E Scarpellini

R Vos

K Blondeau

V Boecxstaens

R Farré

A Gasbarrini

M.D Jan Tack

ON ESOPHAGEAL MOTILITY AND LOWER ESOPHAGEAL SPHINCTER FUNCTION IN MAN

Keywords: itopride, prokinetics, TLESRS, GERD

Introduction: Itopride is a new prokinetic agent which combines antidopaminergic and cholinesterase inhibitory actions. Previous studies suggested that itopride improves heartburn in functional dyspepsia, and decreases esophageal acid exposure in GERD. It is unclear whether this effect is due to effects of itopride on the LES. Aims: To study the effects of itopride on fasting and postprandial LES function in healthy subjects. Materials and methods: twelve healthy volunteers (5 males; 32.6±2.0 years) underwent three esophageal sleeve manometry studies after 3 days premedication with itopride 50 mg, itopride 100mg or placebo t.i.d. Drug was administered after 30 minutes and a standardized meal was administered after 90 minutes, with measurements continuing to 120 minutes postprandially. Throughout the study, 10 wet swallows were administered at 30-minute intervals, and gastrointestinal symptoms were scored on 100 mm visual analogue scales (VAS) at 15-minute intervals. Results: LES resting pressures, swallowinduced relaxations and the amplitude or duration of peristaltic contractions were not altered by both doses of itopride, at all time points. Itopride pretreatment inhibited the meal-induced rise of transient LES relaxations (TLESRs). Conclusions: Itopride inhibits TLESRs without significantly affecting esophageal peristaltic function or LES pressure.

These observations support further studies with itopride in GERD.

INTRODUCTION

Itopride is a novel prokinetic agent acting both as a dopamine D2 receptor antagonist and as an acetylcholine esterase inhibitor. Both animal [START_REF] Iwanaga | Characterization of acetylcholinesteraseinhibition by itopride[END_REF][START_REF] Iwanaga | Gastroprokinetic effect of a new benzamide derivative itopride and its action mechanisms in conscious dogs[END_REF][START_REF] Cellek | potentiation by cholinesterase inhibitors of cholinergic activity in rat isolated stomach and colon[END_REF] and human studies [START_REF] Choung | Trial of itopride (100 and 200 mg three times daily) on gastric motor and sensory function in healthy volunteers[END_REF][START_REF] Holtmann | A placebo-controlled trial of itopride in functional dyspepsia[END_REF] have shown the ability of the drug to accelerate delayed gastric emptying, associated with antiemetic properties. In a phase 2 controlled trial, itopride was superior to placebo in relieving symptoms of functional dyspepsia [START_REF] Holtmann | A placebo-controlled trial of itopride in functional dyspepsia[END_REF]. In a phase 3 program, this superiority was not confirmed, and comparison of both studies suggested that the presence of heartburn, which was excluded in the phase 3 program, was a predictor of response in the phase 2 studies [START_REF] Talley | Itopride in functional dyspepsia: results of two phase III multicentre, randomised, double-blind, placebo-controlled trials[END_REF]. Heartburn is a typical symptom of gastro-esophageal reflux disease (GERD) [START_REF] Vakil | The Montreal definition and classification of gastroesophageal reflux disease: a global evidence-based consensus[END_REF], and a pilot study in GERD patients confirmed the ability of itopride to decrease esophageal acid exposure [START_REF] Kim | Effect of itopride, a new prokinetic, in patients with mild GERD: a pilot study[END_REF]. The mechanisms underlying a potential beneficial effect of itopride in GERD remain to be elucidated.

The pathophysiology of GERD is multifactorial and involves several well-known mechanisms such as failure of the anti-reflux barrier, impaired esophageal clearance, the presence of caustic factors in the refluxate (acid and/or non-acid) and defective esophageal mucosal resistance [START_REF] Ang | Mechanisms of heartburn[END_REF]. The influence of itopride on the anti-reflux barrier has not been studied. Among the dysfunctions of the anti-reflux barrier, transient lower oesophageal sphincter relaxations (TLESRs) are the major mechanism underlying gastrooesophageal reflux events in normal subjects, and in the majority of GERD patients. [START_REF] Ang | Mechanisms of heartburn[END_REF][START_REF] Tack | Anti-relaxation therapy in GORD[END_REF] TLESRs are controlled by a vago-vagal reflex pathway, triggered by activation of stretch receptors of the proximal stomach, and organized in the brain stem, leading to transient relaxation of the lower esophageal sphincter (LES) [START_REF] Tack | Recent developments in the pathophysiology and therapy of gastroesophageal reflux disease and nonerosive reflux disease[END_REF]. Pharmacological inhibition of TLESRs is considered a relevant target for the control of GERD [START_REF] Ang | Mechanisms of heartburn[END_REF]. Several pharmacological agents, including atropine, morphine, GABA-B agonists, cholecystokinin 1 receptor antagonists and nitric oxide synthase inhibitors, have been shown to inhibit the occurrence of transient lower oesophageal sphincter relaxations [START_REF] Tack | Recent developments in the pathophysiology and therapy of gastroesophageal reflux disease and nonerosive reflux disease[END_REF][START_REF] Boeckxstaens | Reflux inhibitors: a new approach for GERD?[END_REF].

The aim of the present study was to investigate the effect of itopride on oesophageal and lower oesophageal sphincter function in healthy subjects, with a focus on the occurrence of TLESRS.

MATERIALS AND METHODS

Subjects

Studies were performed in 12 healthy volunteers (five men and seven women; mean age, 32.6±2.0 years; range, 23-41 years) with a mean body mass index of 22.2±0.9 kg/m 2 .

None of the subjects had symptoms or a history of gastrointestinal disease or upper gastrointestinal surgery, nor were they taking any medication. Written informed consent was obtained from each subject and the study protocol had been approved previously by the Ethics Committee of the University Hospital.

Study design

All subjects underwent the studies after 3 days premedication with itopride 50 mg, itopride 100mg or matching placebo t.i.d. in a double-blind randomised cross-over design.

Treatment periods occurred at least one week apart. On each day of measurements, subjects were studied after an overnight fast of at least 12 hours. A summary of the protocol is shown in Figure 1. Together with a stationary manometry probe, a pH assembly was passed through the nose under topical anesthaesia and positioned with the pH electrode at 5 cm above the LES. After placement of the assembly, the subjects remained in a sitting position for a habituation period of 20 minutes. This period allowed baseline assessment of esophageal peristalsis and LES function. Ten wet swallows of 5 ml of water were administered at 1-minute interval and followed by ingestion of itoprode or placebo according to the double-blind, randomized cross-over design. During the 30 min after administration of the drug oesophageal and lower oesophageal sphincter pressure and oesophageal pH were continuously monitored. Sixty minutes after drug administration the subjects ingested a mixed liquid meal (400 mL, 600 kcal, 13% proteins, 48% carbohydrates, 39% lipids; Nutridrink®, Nutricia, Bornem, Belgium) and recordings continued for 2 hours after the meal. Throughout the study, 10 wet swallows of 5 ml of water were administered at 30-minute intervals.

Recording methods

Following an overnight fast, an oesophageal manometric catheter fitted with a 6-cm Dent Sleeve was introduced through the mouth. Subsequently, the oesophageal catheter was positioned so that pressures could be recorded from the gastric fundus (side hole 2 cm below the sleeve), the LES (sleeve), oesophageal body (side holes 4, 7 and 10 cm proximal to the sleeve) and pharynx (side hole 28 cm proximal to the sleeve, to detect swallows). The oesophageal catheter was infused at a flow rate of 0.5 mL/min with distilled water using a low-compliance pneumo-hydraulic capillary infusion system (Arndorfer Medical Specialties, Milwaukee, WI, USA). The infusion system was connected to external pressure transducers, and signals were recorded on a polygraph (Synectics Medical, Stockholm, Sweden).

The oesophageal pH was measured with an antimony pH electrode (Synectics Medical, Stockholm, Sweden) positioned 5 cm above the proximal margin of the sleeve. The pH electrode was calibrated in buffers of pH 1 and pH 7 before and after each study. During the study period, the oesophageal pH was recorded continuously using an ambulatory data-logger (MicroDigitrapper, Synectics Medical, Stockholm, Sweden).

Data analysis

Lower oesophageal motility

The basal lower oesophageal sphincter pressure was measured at end-expiration relative to the end-expiratory intra-gastric pressure. The basal lower oesophageal sphincter pressure was visually determined every 3 min and averaged over 30-min intervals.

Oesophageal pH

The percentage of time with an oesophageal pH<4 and the number of acid reflux episodes were calculated. Acid reflux episodes were defined as a decrease in oesophageal pH to a value below pH 4 for at least 4 s or as a rapid drop of at least 1 pH unit if the pH was already below 4.

Statistical analysis

Based on previous studies, the study had an 85% power to detect 30% difference in TLESR rate at the 5% significance level. The changes in the basal LES pressure were evaluated using analysis of variance for repeated measures. The changes in TLESRs were analyzed using analysis of variance for repeated measures and Tukey-Kamer multiple comparisons post-test correction. P < 0.05 was considered to be statistically significant. Data are presented as the mean ± standard error of the mean (S.E.M.).

F

RESULTS

Conduct of the study

The positioning of oesophageal manometry catheter and pH probe were all well tolerated, and all subjects completed the three sessions of studies as planned.

Lower esophageal sphincter pressure

Prior to drug administration, LES resting pressure and swallow-induced relaxations were similar for all 3 conditions (Table 1 1).

Oesophageal motility

Both the amplitude or duration of peristaltic contractions were not significantly altered by both doses of itopride in the pre-prandial and post-prandial periods (Table 1). Swallowinduced relaxations were not altered by either dose of itopride at any time point (Table 2).

Swallowing rate

Both before and after the meal, the swallowing rate was significantly altered by itopride 100 mg. However, the 50 mg dose was associated with a significant rise in swallowing rate compared to placebo, both before and after the meal ( did not differ significantly between the treatment conditions (Table 3).

Oesophageal pH monitoring

The percentage of time pH < 4 in the oesophagus did not differ between the itopride and placebo studies in the pre-prandial (0.3 ± 0.1%; 0.3 ± 0.2 % and 0.8 ± 0.5 %, for placebo, itopride 50 mg and itopride 100 mg respectively; NS) and postprandial periods (0.3 ± 0.1%; 0.4 ± 0.1 and 0.3 ± 0.2 %, for placebo, itopride 50 mg and itopride 100 mg respectively; NS).

The number of acid reflux episodes during the post-prandial period after itopride was not significantly different from that after placebo (Figure 3). The number of acid reflux episodes was significantly increased postprandially in the placebo and itopride 100 mg groups, but not in the 50 mg group. Individual data showed a decrease in reflux episodes in all subjects after 100 mg, except for one subject who had a very high rate of reflux episodes under this dose. No significant differences in symptom scores (calculated as area under the curve, AUC)

Symptoms and side effects

during both the pre-prandial and post-prandial periods were found between the itopride and placebo studies (details not shown).

DISCUSSION

The analysis of phase 2 and phase 3 clinical trials with itopride in FD, as well as a small pH monitoring study in patients with heartburn suggested a beneficial effect of itopride in GERD [START_REF] Holtmann | A placebo-controlled trial of itopride in functional dyspepsia[END_REF][START_REF] Talley | Itopride in functional dyspepsia: results of two phase III multicentre, randomised, double-blind, placebo-controlled trials[END_REF][START_REF] Kim | Effect of itopride, a new prokinetic, in patients with mild GERD: a pilot study[END_REF]. In order to elucidate the underlying mechanism, we studied the influence of 2 doses of itopride in a double-blind placebo-controlled cross-over study on pre-and postprandial esopahgeal motility in healthy volunteers. Our main finding was that itopride inhibited the post-prandial increase in the rate of TLESRS without significantly affecting post-prandial LES pressure. Esophageal body peristalsis was also not altered by itopride.

Inhibition of TLESRS is a now well-established therapeutic target in GERD, and this effect may help to explain clinical effects of itopride on heartburn and on esophageal acid exposure [START_REF] Holtmann | A placebo-controlled trial of itopride in functional dyspepsia[END_REF][START_REF] Talley | Itopride in functional dyspepsia: results of two phase III multicentre, randomised, double-blind, placebo-controlled trials[END_REF][START_REF] Kim | Effect of itopride, a new prokinetic, in patients with mild GERD: a pilot study[END_REF]. On the other hand, itopride did not affect esophageal acid exposure in the present study, and the rise in postprandial acid reflux events was only significantly inhibited in the 50 mg group, with some evidence of large inter-individual variability in the 100 mg group. The lack of major effects on these reflux parameters is probably attributable to the fact that this study recruited healthy volunteers, and not GERD patients, and the relatively low sample size. Confirmation of these effects in a larger group of GERD patients seems warranted.

The mechanism underlying the inhibition of TLESRs by itopride remains to be established.

In the absence of effects on esophageal peristalsis and LES resting pressure, esophageal motility does not seem to be the target for itopride in TLESR inhibition. TLESRs are controlled by a vago-vagal reflex pathway which is triggered by gastric distention, integrated in the brainstem and induces release of nitric oxide from intrinsic nerves at the LES [START_REF] Tack | Anti-relaxation therapy in GORD[END_REF][START_REF] Tack | Recent developments in the pathophysiology and therapy of gastroesophageal reflux disease and nonerosive reflux disease[END_REF][START_REF] Boeckxstaens | Reflux inhibitors: a new approach for GERD?[END_REF]. The absence of an influence of itopride on swallow-induced LES relaxations, which are also mediated by intrinsic nitrergic nerves, argues against an effect of itopride at this level. Itopride does have the potential to affect the occurrence of TLESRs at the level of triggering through distention of the proximal stomach. Both positron emission tomography studies and gastric barostat studies showed a decreased postprandial volume of the proximal stomach in healthy volunteers after itopride pretreatment [START_REF] Choung | A double-blind, randomized, placebo-controlled trial of itopride (100 and 200 mg three times daily) on gastric motor and sensory function in healthy volunteers[END_REF][START_REF] Akyuz | Influence of itopride and domperidone on gastric tone and on the perception of gastric distention in healthy subjects[END_REF]. Finally, an effect of itopride, which is likely to cross the blood-brain-barrier [START_REF] Katagiri | Effects of itopride hydrochloride on plasma gut-regulatory peptide and stress-related hormone levels in healthy human subjects[END_REF], on integration of TLESRs in the brainstem cannot be excluded, but is difficult to study in man. The effect of itopride on TLESRs seems to lack a clear dose-dependency. This could in part be due to some increased variability with the 100 mg dose, as illustrated in Figure 3.

However, itopride has a dual pharmacological action as it acts both as a dopamine-2 receptor antagonist and as an acetylcholine esterase inhibitor. It is unclear which one of these pharmacological properties underlies the observed effect on TLESRs. For domperidone, another dopamine-2 antagonist, conflicting data are found in the literature regarding its clinical efficacy in GERD [START_REF] Ramirez | Review article: promotility drugs in the treatment of gastrooesophageal reflux disease[END_REF][START_REF] Pritchard | Should domperidone be used for the treatment of gastro-oesophageal reflux in children? Systematic review of randomized controlled trials in children aged 1 month to 11 years old[END_REF][START_REF] Grande | Lack of effect of metoclopramide and domperidone on esophageal peristalsis and esophageal acid clearance in reflux esophagitis. A randomized, double-blind study[END_REF], but its effects on TLESRs have not been studied to date. In a preliminary study, decreased postprandial gastric volumes, measured with the barostat, were also reported in healthy volunteers treated with domperidone [START_REF] Akyuz | Influence of itopride and domperidone on gastric tone and on the perception of gastric distention in healthy subjects[END_REF].

Besides D2 receptor antagonism, itopride also exerts cholinesterase inhibitory action. In a gastric barostat study in healthy volunteers, a cholinesterase inhibitor did not alter proximal stomach volume, but increased the number of phasic contractions [START_REF] Stefano | Neostigmine-induced postprandial phasic contractility in the proximal stomach and dyspepsia-like symptoms in healthy volunteers[END_REF]. It is less likely that this would result in decreased triggering of TLESRs, but the effect of cholinesterase inhibition on TLESRs has not been investigated so far. Conversely, acetylcholine receptor antagonism has been shown to inhibit the occurrence of TLESRs, probably via a central site of action [START_REF] Fang | Cholinergic blockade inhibits gastro-oesophageal reflux and transient lower oesophageal sphincter relaxation through a central mechanism[END_REF]. It is conceivable, but unproven to date, that enhanced cholinergic activity, induced by a cholinesterase inhibitor, might thus lead to enhanced occurrence of TLESRs. If this is indeed the case, higher doses of itopride exerting higher cholinesterase inhibition levels might act to enhance rather than inhibit TLESRs, and this could have contributed to the lack of a dose-dependent effect of itopride in the present study. A decreased rate in swallowing has been implicated in the effects of baclofen on TLESRs and reflux events ( 23), but we only observed a modest but significant increase in swallowing rate with the 50 mg dose of itopride.

The present study has a number of limitations. First, the number of reflux events and the number of TLESRs are generally low. This is probably attributable to the selection of asymptomatic healthy subjects with a normal body mass index, and the small size and caloric content of the meal. Second, the liquid meal may lead to more rapid buffering of intragastric acid, thereby under-estimating reflux events when pH monitoring is used.

Taken together, it is conceivable that a larger therapeutic effect could be obtained in a population of GERD patients, using a larger meal. Furthermore, the study set-up used two independent systems to monitor manometry and reflux events. Hence, reliable analysis of the motor events underlying the reflux patterns is not possible. The current status seems to be that development for US or EU in the functional dyspepsia indication has been abandoned.

I think we need one figure showing the data for individuals -perhaps the total TSELRs for placebo and the 2 doses, with the data points joined... how consistent is the effect? I'd prefer this approach for the final figure -it tells the reader so much more than histograms.

We agree and added graphs with individual data Reviewer: 2 Comments for Transmission to the Authors The authors investigated the effects of the new prokinetic agent, itopride, on esophageal and LES function in healthy subjects. The study was conducted in a double blind crossover control trial with a one week washout period in normal volunteers. The authors show that this agent inhibits TLESRs but has little to no effect on esophageal peristalis or LES pressure. The experimental protocol is well described and the data is convincingly shown. The figure quality is poor and detracts from the relative importance of these findings.

As also pointed out by reviewer 3, Figure and Table 3 overlap. We have deleted Figure 3 and we have replaced it by individual numbers figures to better illustrate the effects of the drug.

The statistical analysis should be better described given the small sample size of ten subjects.

We have elaborated on power calculations and statistical analysis. We have now also added ANOVA with repeated measure analysis.

The major drawback from this study design is that the authors have selected normal volunteers to test this agent, however the authors recognize this relative weakness to the study design and have included this in the discussion section.

We agree and have included this in the discussion. (for your information: a patient study will start before the end of this year).

A proposed mechanism of action of the D2 antagonist/anticholinesterase would enhance the discusson section.

We have added a section on the relative contribution of both pharmacological mechanisms in the discussion section, highlighted in the revised version. Reviewer: 3 Comments for Transmission to the Authors Aim of this study was to evaluate the role of itopride on fasting and postprandial oesophageal and LES motility in healthy subjects. Oesophageal pH was also recorded with a ambulatory data logger.

Results have shown that itopride inhibited meal-induced rise in TLESRs. Acid reflux was unaffected. Interesting study. A few issues should be raised: -A dose effect of itopride on rate of TLESRs was not seen. The authors should discuss this.

We agree and have added a section in the discussion -Comparisons among fasting, first and second postprandial hour should be done with tests for multiple comparisons and not t-test or the Wilcoxon test.

We agree and have adapted the statistics; we used ANOVA with repeated measures and Tukey Cramer post test correction for multiple comparisons.

-The liquid formula used is not an optimal meal: substantial intragastric acid buffering induced by this type of meal decreases occurrence of acid reflux, making it harder to see differences between different experimental conditions. Furthermore the postprandial rate of TLESRs is low even during placebo compared to similar studies in healthy volunteers. The authors should discuss these points.

We agree and this was addressed discussion section.

-a limitation of this study was that manometry and pH recording were performed with two independent systems, therefore analysis of motor events underlying reflux episodes could not be done. The authors should acknowledge this.

We agree and this was added to the discussion section.

-the rate of swallowing has been shown to be decreased by drugs affecting the rate of TLESRs. The authors should report the rate of spontaneous swallowinedg in order to better interpret the results.

We have added data on swallowing rate.

-BMI instead of body weight should be used This is corrected -Table 3 should be avoided

We agree that Table 3 This is corrected.

  Itopride and esophageal functionScarpellini et al., 4

  Itopride and esophageal functionScarpellini et al., 9

  Itopride and esophageal functionScarpellini et al., 11

FIGURESFigure 1 .

 1 FIGURES

Figure 2 .

 2 Figure 2. Individual numbers of total transient LES relaxations for the 3 treatment conditions.

Figure 3 .

 3 Figure 3. Acid reflux episodes for the 3 treatment conditions, before and after the meal. * = p< 0.05 compared to preprandial.

  Throughout the study, the sensations of

	fullness, nausea, heartburn, belching, satiety, hunger, anxiety, dizziness, sleepiness and
	fatigue were measured every 15 min using validated 100-mm visual analogue scales.
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Table 3

 3 ).The numbers of transient lower oesophageal sphincter relaxations after the administration of placebo and itopride are summarized in Figure2and Table4. After placebo, ingestion of the meal was associated with a significant increase in the rate of transient lower oesophageal sphincter relaxations during the first and the second post-prandial hour (ANOVA, p<0.001). After itopride 50 mg, no significant rise of TLESR rate was observed during the first postprandial hour (ANOVA, p>0.05), and in a paired comparison, the rate of TLESRs was significantly lower than after placebo during the first hour (t-test, p<0.05).After itopride 100 mg, no significant rise of TLESR rate was seen during the first and the

	Transient lower esophageal sphincter relaxations
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second postprandial hour (ANOVA, p>0.05), and the rate of TLESRs was significantly lower than after placebo during the second hour (t-test, p<0.05). The duration of TLESRS

Table 1 .

 1 TABLES Esophageal motility parameters for the 3 treatment conditions, before and after drug intake, and before and after the meal. No significant differences between groups occurred. *p<0.05 compared to basal.

			Placebo	Itopride 50 mg	Itopride 100 mg
	LES pressure	Basal	19.7±2.5	15.8±2.8	20.2±3.0
	(mm Hg)	Post-drug	17.3±3.0	11.8±1.6	19.8±3.7
		Postprandial	10.3±1.5 *	8.3±1.5 *	11.1±1.8 *
		1 st hour
		Postprandial	8.6±3.0 *	10.0±2.0	8.8±4.8 *
		2 nd hour
	Distal	Basal	76.0 ±3.4	78.4 ± 4.3	76.9 ± 3.7
	contraction	Post-drug	83.0 ± 4.8	80.2 ± 4.2	86.2 ± 2.9
	amplitude (mm	Postprandial	78.6 ± 3.6	76.8 ± 3.1	79.5 ± 3.9
	Hg)	1 st hour
		Postprandial	73.9 ± 4.3	73.3 ± 2.9	76.9 ± 4.1
		2 nd hour
	Distal	Basal	4.6 ± 0.3	5.2 ± 0.4	4.8 ± 0.3
	contraction	Post-drug	5.0 ± 0.3	5.3 ± 0.4	4.7 ± 0.2
	duration (sec)	Postprandial	5.1 ± 0.3	5.4 ± 0.3	4.7 ± 0.2
		1 st hour
		Postprandial	4.9 ± 0.3	5.2 ± 0.3	4.6 ± 0.2
		2 nd hour

Table 2 .

 2 Characteristics of swallow-induced relaxations for the 3 conditions, before and after drug intake, and before and after the meal. No significant differences occurred between groups or over time.

		Placebo	Itopride 50 mg	Itopride 100 mg
	Relaxation (%)
	Basal	97.7±0.8	97.8±0.7	96.4±0.7
	Post-drug	94.4±1.6	92.4±2.3	96.4±1.2
	Postprandial	92.2±3.9	95.5±1.1	96.8±0.6
	1 st hour
	Postprandial	95.9±1.2	93.3±1.7	93.0±3.0
	2 nd hour
	Duration (sec)
	Basal	11.9±0.4	13.9±0.8	12.8±0.8
	Post-drug	11.3±0.7	13.0±0.5	11.7±0.5
	Postprandial	11.6±0.6	13.4±0.7	11.7±0.7
	1 st hour
	Postprandial	11.7±0.5	13.0±0.5	12.9±0.6
	2 nd hour

Table 3 .

 3 Number of swallows for the 3 treatment conditions, before and after the meal. * p< 0.05 compared to placebo.

	Pretreatment	Pre-prandial	First post-	Second post-	TOTAL
			prandial hour	prandial hour
	Placebo	25.2 ± 2.8	19.0 ± 1.1	20.5 ± 2.2	63.8 ± 5.1
	Itopride 50 mg	27.3 ± 2.3	24.6 ± 2.1*	23.8 ± 1.7	75.8 ± 5.5*
	Itopride 100 mg	25.3 ± 2.7	21.4 ± 2.5	21.9 ± 2.6	63.1 ± 8.4

Table 4 .

 4 Number of transient lower oesophageal sphincter relaxations for the 3 treatment conditions, before and after the meal. * P < 0.05 compared to preprandial. # p< 0.05 compared to placebo.

	Pretreatment	Pre-prandial	First post-	Second post-	TOTAL
			prandial hour	prandial hour
	Placebo	0.3 ± 0.1	1.3 ± 0.2 *	1.7 ± 0.3 *	3.0 ± 0.5 *
	Itopride 50 mg	0.4 ± 0.3	0.5 ± 0.3 #	1.2 ± 0.4 *	1.7 ± 0.7 *
	Itopride 100 mg	0.7 ± 0.2	1.0 ± 0.3	0.4 ± 0.2 #	1.7 ± 0.4 *

  and figure 3 are identical. We have kept the table, and have replaced Figure3with individual data points for the first and second postprandial hour -Fig 2, the evaluated variable is "number of TLESRs" and not "number of TLESRs/hour" -minor point, page 6, line 19: "or as a rapid drop in pH of at least 1 unit if pH already below 4"

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	This is corrected

This study was supported by a Methusalem grant from Leuven University to Prof. Jan Tack and a Rome Foundation Fellowship to Emidio Scarpellini. Ricard Farré and Kathleen Blondeau are postdoctoral research fellows from the FWO Flanders.


Van Oudenhove

PhD Joris Vandenberghe

MD Rita Vos

MSc Lieselot Holvoet

MSc Koen Demyttenaere

MD, PhD Jan Tack

Lukas Van Oudenhove
email: lukas.vanoudenhove@med.kuleuven.be

Dr Lukas Van Oudenhove

RISK FACTORS FOR IMPAIRED HEALTH-RELATED QUALITY OF LIFE IN FUNCTIONAL DYSPEPSIA

Keywords: Functional dyspepsia < Disease-based, Functional GI diseases < Disease-based, Psychiatric disorders < Topics, Outcomes research functional dyspepsia, (health-related) quality of life, psychosocial, psychiatric, somatization, FGID, functional gastrointestinal disorders, HRQoL, health-related mental composite score

Background The influence of patient characteristics on HRQoL in functional dyspepsia (FD) is poorly understood. Aim To determine the contribution of gastric sensorimotor function, psychosocial factors & 'somatization' to HRQoL in FD. Methods In 259 tertiary care FD patients, we studied gastric sensorimotor function with barostat. We measured psychosocial factors and 'somatization' using self-report questionnaires. HRQoL was assessed using the SF-36 physical and mental composite scores (PCS, MCS). Bivariate associations between gastric sensorimotor function, psychosocial factors & 'somatization' on the one hand and PCS and MCS on the other were estimated. Variables significantly associated with PCS or MCS in bivariate analysis were entered into hierarchical multiple linear regression models. Results Mean PCS was 40.1±9.5; mean MCS was 45.1±10.8. 'Somatization' (p<0.0001) and chronic fatigue (p=0.002) were significantly associated with impaired PCS [R²=.52, p<.0001]. The effects of abuse history and depression were 'mediated' by 'somatization'. Trait anxiety (p=.02), alexithymia (p=.06), depression (p=.06), positive affect (p<.0001), negative affect (p=.002) and generalized anxiety disorder (p=.01) were significantly associated with impaired MCS (R²=.67, p<0.0001). Conclusion 'Somatization' is the most important risk factor for impaired physical HRQoL in FD; it 'mediates' the effect of abuse history and depression. Mental HRQoL is mainly explained by psychosocial factors.

Functional dyspepsia (FD) is a highly prevalent functional gastrointestinal disorder (FGID) defined according to 'Rome III criteria' as "presence of symptoms thought to originate in the gastroduodenal region, in the absence of any organic, systemic, or metabolic disease that is likely to explain the symptoms" [START_REF] Tack | Functional Gastroduodenal Disorders[END_REF] . Its etiopathogenesis remains incompletely understood and is likely to be heterogeneous and multifactorial [START_REF] Tack | Functional Gastroduodenal Disorders[END_REF] . According to the 'biopsychosocial model', FGID and other 'functional somatic syndromes' result from a complex and reciprocal interaction between biological, psychological and social factors [START_REF] Van Oudenhove | Recent insights on central processing and psychological processes in functional gastrointestinal disorders[END_REF][START_REF] Drossman | The functional gastrointestinal disorders and the Rome III process[END_REF] .

Impaired health-related quality of life (HRQoL) has been demonstrated in FGID in general and FD in particular, especially in referral populations, but also at the primary care or population level. HRQoL in FGID has been found to be lower compared to the general healthy population as well as compared to patient groups with chronic (organic) disorders, at least in some domains [START_REF] Haag | Is there any association between disturbed gastrointestinal visceromotor and sensory function and impaired quality of life in functional dyspepsia?[END_REF][START_REF] Chang | Review article: epidemiology and quality of life in functional gastrointestinal disorders[END_REF][START_REF] El-Serag | Health-related quality of life in functional dyspepsia[END_REF][START_REF] Talley | Functional dyspepsia, delayed gastric emptying, and impaired quality of life[END_REF][START_REF] Biggs | Effect of childhood adversity on health related quality of life in patients with upper abdominal or chest pain[END_REF][START_REF] Monés | Quality of Life in Functional Dyspepsia[END_REF] . It should be noted, however, that some earlier studies found no difference in HRQoL between FD and healthy controls or patients suffering from organic gastrointestinal (GI) disorders [START_REF] El-Serag | Health-related quality of life in functional dyspepsia[END_REF][START_REF] Biggs | Effect of childhood adversity on health related quality of life in patients with upper abdominal or chest pain[END_REF] , in contrast to most recent studies [START_REF] Haag | Is there any association between disturbed gastrointestinal visceromotor and sensory function and impaired quality of life in functional dyspepsia?[END_REF][START_REF] Talley | Functional dyspepsia, delayed gastric emptying, and impaired quality of life[END_REF][START_REF] Monés | Quality of Life in Functional Dyspepsia[END_REF][START_REF] Jones | Psychosocial correlates of symptoms in functional dyspepsia[END_REF] . Thus, there is some discrepancy in the existing literature.

Understanding risk factors for impaired HRQoL in FGID is important, as these may provide guidance for improving assessment and treatment in this difficult-to-treat condition [START_REF] Chang | Review article: epidemiology and quality of life in functional gastrointestinal disorders[END_REF] . However, research on these risk factors in FD is rather sparse. Gastric sensorimotor function, psychosocial factors (including abuse history, personality traits, affect and psychiatric comorbidity) and 'somatization' (defined as a tendency to experience and report multiple somatic symptoms that cannot be adequately explained by organic findings) may all be potential risk factors [START_REF] Chang | Review article: epidemiology and quality of life in functional gastrointestinal disorders[END_REF] , but they haven't been examined in a single FD study yet. This is especially important as impaired HRQoL in FGID is likely to result from the complex biopsychosocial interplay between these factors [START_REF] Chang | Review article: epidemiology and quality of life in functional gastrointestinal disorders[END_REF] .

However, the influence of some of these factors on HRQoL in FD has been studied recently.

First, dyspepsia symptom levels have been shown to be associated with all domains of 'generic' Van Oudenhove et al HRQoL [START_REF] Talley | Functional dyspepsia, delayed gastric emptying, and impaired quality of life[END_REF][START_REF] Monés | Quality of Life in Functional Dyspepsia[END_REF] , but in other studies, dyspepsia symptoms were only associated with the physical, and not the mental component of HRQoL [START_REF] Jones | Psychosocial correlates of symptoms in functional dyspepsia[END_REF][START_REF] Haag | Impairment of health-related quality of life in functional dyspepsia and chronic liver disease: the influence of depression and anxiety[END_REF][START_REF] Fischler | Heterogeneity of symptom pattern, psychosocial factors, and pathophysiological mechanisms in severe functional dyspepsia[END_REF] . Second, a significant effect of gender was found, with women having lower QoL) in a primary care sample [START_REF] Talley | Functional dyspepsia, delayed gastric emptying, and impaired quality of life[END_REF][START_REF] Welén | Functional dyspepsia affects women more than men in daily life: A case-control study in primary care[END_REF] . Third, a number of studies demonstrated the importance of psychosocial risk factors for impaired QoL. Childhood adversities, including sexual, physical and psychological abuse or neglect, were significantly associated with lower QoL, in the mental and physical domains. The effect on physical QoL was found to be (partially) mediated by "distress", defined as the sum of anxiety and depression scores [START_REF] Biggs | Effect of childhood adversity on health related quality of life in patients with upper abdominal or chest pain[END_REF] . Other studies confirmed the role of anxiety and depression as important risk factors for impaired QoL, although results on their influence on the physical domain of HRQoL vary [START_REF] Haag | Impairment of health-related quality of life in functional dyspepsia and chronic liver disease: the influence of depression and anxiety[END_REF][START_REF] Aa | Quality of life in patients with functional dyspepsia: a prospective 1-year follow-up study in Spanish patients[END_REF] . Finally, Talley et al found at best a weak relationship between gastric emptying and HRQoL 7 ; this finding was replicated very recently [START_REF] Haag | Is there any association between disturbed gastrointestinal visceromotor and sensory function and impaired quality of life in functional dyspepsia?[END_REF] . Importantly, to the best of our knowledge, the influence of 'somatization' on HRQoL has not been studied in FD, despite its established importance as a predictor of HRQoL in irritable bowel syndrome (IBS) [START_REF] Chang | Review article: epidemiology and quality of life in functional gastrointestinal disorders[END_REF] [START_REF] Van Oudenhove | Relationship between anxiety and gastric sensorimotor function in functional dyspepsia[END_REF][START_REF] Van Oudenhove | Determinants of Symptoms in Functional Dyspepsia: Gastric Sensorimotor Function, Psychosocial Factors or Somatization?[END_REF] . However, the data on HRQoL in general and the hypotheses tested in the present study in particular are novel and have not been reported on elsewhere. Further details about patient selection have been published elsewhere [START_REF] Van Oudenhove | Relationship between anxiety and gastric sensorimotor function in functional dyspepsia[END_REF] .

Gastric sensorimotor function testing

Details about gastric sensorimotor function testing have been published elsewhere [START_REF] Van Oudenhove | Relationship between anxiety and gastric sensorimotor function in functional dyspepsia[END_REF][START_REF] Ghoos | Measurement of gastric emptying rate of solids by means of a carbon-labeled octanoic acid breath test[END_REF] . Briefly, we used our standard barostat protocol. During isobaric stepwise distension, patients scored their perception of upper abdominal sensation at the end of every distending step using a graphic rating scale (0-6) with verbal descriptors. Perception, discomfort & pain thresholds were defined as the lowest pressure above minimal distending pressure evoking a perception score of 1 or more, 5 or more & 6 or more, respectively, based on previous studies from our group [START_REF] Van Oudenhove | Relationship between anxiety and gastric sensorimotor function in functional dyspepsia[END_REF][START_REF] Van Oudenhove | Determinants of Symptoms in Functional Dyspepsia: Gastric Sensorimotor Function, Psychosocial Factors or Somatization?[END_REF][START_REF] Tack | Symptoms associated with hypersensitivity to gastric distention in functional dyspepsia[END_REF][START_REF] Sarnelli | Reproducibility of gastric barostat studies in healthy controls and in dyspeptic patients[END_REF] . Meal-induced gastric relaxation (accommodation) was quantified as the difference between the average volumes during 30 minutes before and 60 minutes after meal administration. In all patients who did not recently undergo a gastric emptying study at another institution (n=154), gastric emptying for solids was measured using the previously validated [START_REF] Aa | Quality of life in patients with functional dyspepsia: a prospective 1-year follow-up study in Spanish patients[END_REF] Coctanoic acid breath test. Gastric half-emptying time (t 1/2 ) for solids was calculated as previously described [START_REF] Ghoos | Measurement of gastric emptying rate of solids by means of a carbon-labeled octanoic acid breath test[END_REF] . The sexual and physical abuse questionnaire, developed and validated in a GI population by Leserman et al, was filled out on the day of the study together with the self-report questionnaires (i.e. questionnaires that were completed by the participants themselves, without involvement of an interviewer) described below. This questionnaire yields dichotomous answers for both sexual and physical abuse during childhood and adulthood [START_REF] Leserman | The reliability and validity of a sexual and physical abuse history questionnaire in female patients with gastrointestinal disorders[END_REF] .

Abuse history measurements

'Trait' psychological factors

Alexithymia

Alexithymia is a stable psychological trait consisting of three dimensions: difficulty identifying feelings & distinguishing between feelings and bodily sensations, difficulty describing feelings and externally oriented thinking [START_REF] De Gucht | Alexithymia and somatisation: A quantitative review of the literature[END_REF][START_REF] Taylor | The 20-Item Toronto Alexithymia Scale: IV. Reliability and factorial validity in different languages and cultures[END_REF] . In this study, the well-validated 20-item Toronto Alexithymia Scale was used to assess alexithymia, yielding continuous scores (total as well as subscales for the three dimensions) [START_REF] Taylor | The 20-Item Toronto Alexithymia Scale: IV. Reliability and factorial validity in different languages and cultures[END_REF] .

Trait anxiety

The 20-item trait scale of the State-Trait Anxiety Inventory measures stable individual differences in "anxiety proneness", that is "differences between people in the tendency to perceive situations as threatening and to respond to them with elevations in state anxiety" [START_REF] Spielberger | Manual for the State-Trait Anxiety Inventory (form Y Self-evaluation Questionnaire)[END_REF][START_REF] Van Der Ploeg | Handleiding bij de Zelf-Beoordelings Vragenlijst [Manual for the Dutch adaptation of the STAI-Y[END_REF] and yields a continuous total score.

'State' psychological factors & psychiatric disorders measurements

Depression

The depression module of the Patient Health Questionnaire (PHQ-9) was used to screen for depressive comorbidity according to the Diagnostic and Statistical Manual of Mental Disorders, 4 th edition (DSM-IV) [START_REF] Kroenke | The PHQ-9. Validity of a Brief Depression Severity Measure[END_REF][START_REF]Diagnostic and Statistical Manual of Mental Disorders[END_REF] . The 9 DSM-IV depressive symptoms (past two weeks) are rated on a Likert scale (0-3). Depression score (sum of the 9 items) was used as a continuous variable.

Anxiety disorders

The anxiety disorder module of the PHQ allows a diagnosis (yes/no) of current DSM-IV panic disorder and generalized anxiety disorder using the recommended algorithm [START_REF] Lowe | Detecting panic disorder in medical and psychosomatic outpatients: Comparative validation of the Hospital Anxiety and Depression Scale, the Patient Health Questionnaire, a screening question, and physicians' diagnosis[END_REF][START_REF] Spitzer | Validation and Utility of a Self-report Version of PRIME-MD: The PHQ Primary Care Study[END_REF] .

Positive & Negative Affect

The Positive And Negative Affect Schedule (PANAS), consisting of two 10-item mood scales measuring positive affect & negative affect over the past two weeks, was used in this study [START_REF] Watson | Development and Validation of Brief Measures of Positive and Negative Affect: The PANAS Scales[END_REF] .

Somatic symptoms measurements

'Somatization'

The PHQ somatoform disorder module (PHQ-15) is a well-validated self-report questionnaire composed of 15 somatic symptoms, including 14 of the 15 most prevalent DSM-IV somatization disorder criteria [START_REF]Diagnostic and Statistical Manual of Mental Disorders[END_REF][START_REF] Kroenke | The PHQ-15: validity of a new measure for evaluating the severity of somatic symptoms[END_REF] . All items are rated on a Likert scale (0 to 2). Current 'somatization' (past month) was measured.

To avoid overlap with the PHQ-9 depression measure, which may be problematic in the multiple regression models, we did not take into account the two somatic depression items (taken from the PHQ-9) included in the PHQ-15. Thus, the 'somatization' score we used throughout the study is the sum of the remaining thirteen items. It should be noted that this abbreviated version is not a validated instrument, which should be considered a limitation.

Moreover, a limitation of the PHQ-15 as a self-report measure (without interview) is that it cannot distinguish between 'medically explained' and 'unexplained' symptoms [START_REF] Kroenke | The PHQ-15: validity of a new measure for evaluating the severity of somatic symptoms[END_REF] , which is an important feature of the 'somatization' concept [START_REF] De Gucht | Somatization: A Critical Review of Conceptual and Methodological Issues[END_REF][START_REF] Lipowski | Somatization: the concept and its clinical application[END_REF] . In this study, adequate clinical and technical investigations were performed to rule out a medical explanation of GI symptoms, but not systematically of other somatic symptoms as included in the PHQ-15, although major non-GI medical co-morbidity that may account for these somatic symptoms was ruled out on an "as needed" basis. Nevertheless, it should be emphasized that the PHQ symptom count in this study can only be characterized as indicative of 'somatization'. However, total self-reported PHQ somatic symptom counts are highly associated with physician-rated somatoform disorder symptom counts [START_REF] Kroenke | The PHQ-15: validity of a new measure for evaluating the severity of somatic symptoms[END_REF][START_REF] Kroenke | A Symptom Checklist to Screen for Somatoform Disorders in Primary Care[END_REF] . Furthermore, the distinction between medically explained and unexplained symptoms may be problematic and less relevant than previously thought [START_REF] Creed | Can DSM-V facilitate productive research into the somatoform disorders?[END_REF][START_REF] Kroenke | Physical symptom disorder: A simpler diagnostic category for somatization-spectrum conditions[END_REF][START_REF] Mayou | Somatoform Disorders: Time for a New Approach in DSM-V[END_REF][START_REF] Barsky | Somatization Increases Medical Utilization and Costs Independent of Psychiatric and Medical Comorbidity[END_REF] On the day of the study, the intensity of 9 dyspeptic symptoms was scored on a Likert scale [0-3 (absent, mild, moderate, severe)], as previously reported. Dyspepsia symptom score is defined as the sum of all 9 items 38 .

Weight loss

Weight loss since the onset of dyspepsia symptoms was determined by self-report at the inclusion outpatient clinic visit (i.e. patients were weighed and were asked about the amount of weight loss since the onset of their dyspepsia symptoms.

IBS

IBS was assessed with a previously used 10-item yes/no self-report questionnaire assessing the Rome II criteria for IBS [START_REF] Fischler | Heterogeneity of symptom pattern, psychosocial factors, and pathophysiological mechanisms in severe functional dyspepsia[END_REF] .

Chronic fatigue symptoms

Chronic fatigue was considered present when the answers on two yes/no screening questions regarding duration (> 6 months) of and disability due to fatigue were positive. It should be noted as a limitation that this can only be seen as indicative of comorbid chronic fatigue as a symptom, not as a full assesment of chronic fatigue syndrome according to its diagnostic criteria.

Health-related quality of life measurement

The SF-36 Health Survey (version 1), a widely used and validated measure of generic (as opposed to disease-specific) HRQoL, was used in its "standard" version (i.e. employing a 4-week time frame) [START_REF] Ware | SF-36 Physical & Mental Health Summary Scales: A Manual for Users of Version 1[END_REF][START_REF] Aaronson | Translation, Validation, and Norming of the Dutch Language Version of the SF-36 Health Survey in Community and Chronic Disease Populations[END_REF] . The SF-36 is composed of 36 questions and standardized response choices, organized into eight multi-item scales: physical functioning, role limitations due to physical health problems, bodily pain, general health perceptions, vitality, social functioning, role limitations due to emotional problems, and general mental health. All raw scale scores are linearly converted to a 0 to 100 scale, with higher scores indicating higher levels of functioning population norms has been shown to make a minimal difference compared to scoring based on country-specific norms and has been recommended for comparing results from different countries [START_REF] Jr | The Equivalence of SF-36 Summary Health Scores Estimated Using Standard and Country-Specific Algorithms in 10 Countries: Results from the IQOLA Project[END_REF] . Based on these norm-based scores for each scale, physical and mental composite scores (PCS, MCS) can be calculated [START_REF] Ware | SF-36 Physical & Mental Health Summary Scales: A Manual for Users of Version 1[END_REF][START_REF] Aaronson | Translation, Validation, and Norming of the Dutch Language Version of the SF-36 Health Survey in Community and Chronic Disease Populations[END_REF] . We will use norm-based scores for all SF-36 scores throughout the article because of the ease of interpretation; all data from other studies were converted to NBS for comparison purposes.

Statistical analysis SAS 9.2 and Enterprise Guide 4.2 (SAS Institute, Cary, NC) were used. If a certain variable(s) was (were) missing for a patient, this patient was excluded form all analyses in which the missing variable(s) was (were) used. Data are presented as mean ± standard deviation. Significance level was set at p=0.05.

First, bivariate association measures between gastric sensorimotor variables, abuse history, 'trait' and 'state' psychological variables and somatic symptom variables on the one hand and SF-36 PCS or MCS on the other were calculated using Spearman's correlations for continuous variables and Kruskal-Wallis test for categorical variables, as some of the variables were not normally distributed.

Second, two different multiple linear regression models were built with PCS and MCS as the dependent variables. Gastric sensorimotor variables, abuse history, 'trait' and 'state' psychological variables and somatic symptom variables that were bivariately associated with the dependent variable (p<0.05) were entered into the regression model as independent variables in a hierarchical way. Tolerances were used to check potential multicollinearity, with tolerance <0.25 being the criterion to remove a variable from the model. Sociodemographics were controlled for when needed (i.e. when associated with the dependent variables in bivariate analysis). Gastric sensorimotor variables were entered in the first step, abuse history variables in the second step, 'trait' psychological variables in the third step, 'state' psychological variables in the fourth step and somatic symptom variables in the final step. Although it remains to a speculative given the cross-sectional nature of the present data, this order was chosen because it reflects the putative temporal order of events leading to impaired HRQoL best. For example, sexual/physical abuse has been shown to be a risk factor for 'trait' psychological factors, 'state' psychiatric comorbidity and 'somatization' in longitudinal studies [START_REF] Chen | Sexual abuse and lifetime diagnosis of psychiatric disorders: systematic review and meta-analysis[END_REF][START_REF] Paras | Sexual Abuse and Lifetime Diagnosis of Somatic Disorders: A Systematic Review and Meta-analysis[END_REF][START_REF] Rademaker | Self-reported early trauma as a predictor of adult personality: a study in a military sample[END_REF] and psychiatric comorbidity has been demonstrated to be a risk factor rather than a consequence of functional somatic symptoms [START_REF] Janssens | Anxiety and depression are risk factors rather than consequences of functional somatic symptoms in a general population of adolescents: The TRAILS study[END_REF][START_REF] Sykes | Psychopathology in Irritable Bowel Syndrome: Support for a Psychophysiological Model[END_REF] . Moreover, entering variables in this order (especially 'somatization' in the last step) can give an indication about the putative mediational effects formulated in the hypothesis. Although it should be noted that in principle, it is not theoretically possible to study mediation in a cross-sectional sample because it assumes temporal precedence (see definition below in this paragraph). Therefore, the term 'mediation' as used throughout this article should be interpreted in a more limited sense, i.e. devoid of its temporal precedence aspect. However, we decided to use the term 'mediation' as the order in which variables were entered may well reflect the putative temporal order of events based on the literature (see above).

When potential 'mediation' was detected in the hierarchical regression model, the mediation hypothesis was further tested as described by Baron and Kenny, and the Sobel test was used to test significance of the indirect (i.e. mediation) effect [START_REF] Baron | The moderator-mediator variable distinction in social psychological research: conceptual, strategic, and statistical considerations[END_REF] .

We will use the classification of risk factors formulated by Kraemer et al throughout this article [START_REF] Kraemer | How Do Risk Factors Work Together? Mediators, Moderators, and Independent, Overlapping, and Proxy Risk Factors[END_REF] . Briefly, in this influential paper from the psychiatric literature, the authors distinguish between the following types of risk factors. First, mediation implies that two risk factors A & B are mutually associated, A precedes B and when A & B are considered jointly as risk factors for the outcome, B dominates A (i.e. the effect of A is turned non-significant when B is entered into the model). Second, independent risk factors are not mutually associated, no temporal precedence is assumed and when considered jointly, both risk factors are significantly associated with the outcome. Third, overlapping risk factors are mutually associated, no temporal precedence is assumed and when considered jointly, both risk factors are significantly associated with the outcome. Van Oudenhove et al 330 FD patients were asked to participate at the GI outpatient clinic. There were 4 refusals to participate at the clinic visit (1.2% of the total sample). 46 patients (13.9%) cancelled their study visit or didn't show up, allowing 280 barostat investigations to be performed. In 21 patients (6.4%), the procedure had to be stopped prematurely as patients didn't tolerate tube insertion or had severe discomfort once the tube was inserted. 259 patients (78.5%) completed the study (Figure 1). 195 patients (75.3% of the completers) were women; the mean age was 39.5± 12.9 years.

RESULTS

Patient characteristics

HRQoL descriptive statistics

The mean norm-based scores for the [START_REF] Ware | SF-36 Physical & Mental Health Summary Scales: A Manual for Users of Version 1[END_REF] and Dutch 40 population norms, and other studies in FD 4, 7-9, 49, 50 , IBS [START_REF] Ca | Irritable bowel syndrome in France: quality of life, medical management, and costs: the Encoli study[END_REF][START_REF] Jones | Quality of Life in Patients With Inflammatory Bowel Disease and Irritable Bowel Syndrome Differs Between Subjects Recruited from Clinic or the Internet[END_REF][START_REF] Berg | Quality of life of patients with irritable bowel syndrome is low compared to others with chronic diseases[END_REF][START_REF] Dean | Impairment in work productivity and health-related quality of life in patients with IBS[END_REF] in Figure 2. PCS and MCS were not significantly correlated (ρ=-0.05, p=0.43), which supports the concept of them being two distinct aspects of HRQoL.

Bivariate associations

Significant bivariate associations are shown in Table 1.

Impaired PCS was associated with sociodemographics (female gender, employment status), gastric sensorimotor function (lower discomfort threshold, slower gastric emptying), abuse history (overall adult abuse), 'state' psychiatric comorbidity/psychological factors (depression, positive affect) and somatic symptom variables ('somatization', dyspepsia symptoms, weight loss and chronic fatigue).

Impaired MCS was not associated with sociodemographics, gastric sensorimotor function or any any somatic symptom variable. Associations were found with abuse history (overall adult abuse), 'trait' psychological factors (trait anxiety and alexithymia) and 'state' psychiatric

Multiple linear regression

Chronic fatigue (p=0.002) and, most strongly, 'somatization' (p<0.0001) were significant risk factors for impaired PCS in the final model, with employment status (p=0.06) and dyspepsia symptom score (p=0.07) showing a trend (Table 2). The model was highly significant (p<0.0001) and explained 52% of the variance in PCS. As chronic fatigue and 'somatization' are significantly associated (Kruskal-Wallis χ²=21.1, p<0.0001), they can be considered overlapping risk factors for impaired PCS [START_REF] Kraemer | How Do Risk Factors Work Together? Mediators, Moderators, and Independent, Overlapping, and Proxy Risk Factors[END_REF] . Overall adult abuse history and depression were significant risk factors for impaired PCS before 'somatization' was entered into the model, which may be indicative of 'mediation' (in its limited sense defined in the methods section) of their effect on PCS by 'somatization'. Further formal testing confirmed this 'mediation' hypothesis in both cases (Figure 3a-b). Significance of both indirect effects was confirmed using the Sobel test (Z=-3.11, p=0.002 and Z=-4.12, p<0.0001, respectively). When gastric emptying was entered together with gastic discomfort threshold in step 1 of the model (controlling for gender and employment status), emptying was not significantly associated with PCS (β±SE 0.002±0.02, p=0.92). Given the relatively high number of missing values for emptying and the lack of significance, emptying was not included in the models shown in Table 2. No multicollinearity was detected (all tolerances > 0.50).

Significant risk factors for impaired MCS in the final model were trait anxiety (p=0.02), presence of generalized anxiety disorder (p=0.01), negative affect (p=0.002) and positive affect (p<0.0001); a trend was observed for alexithymia (p=0.06) and depression (p=0.06) (Table 3).

The model was highly significant (p<0.0001) and explained 66% of the variance in MCS. Given the fact that all these variables are mutually associated (data not shown), they should be considered overlapping risk factors for impaired MCS [START_REF] Kraemer | How Do Risk Factors Work Together? Mediators, Moderators, and Independent, Overlapping, and Proxy Risk Factors[END_REF] . However, given the fact that the magnitude of the associations between the independent variables was small to moderate, no multicollinearity was detected in the multiple regression model (all tolerances > 0.38).

HRQoL scores

In the present study, PCS and MCS in tertiary care FD were 1 and 0.5 standard deviation below population norms, respectively. If these scores are compared to other studies in FGID (Figure 2A), the present PCS score is at the lower end of the range, whereas the present MCS score is at the higher end. This figure also shows that in IBS, PCS tends to be higher and MCS tends to be lower compared to FD. If we look at the individual scale scores (Figure 2B), patients in the present study score particularly low on the role limitations physical, bodily pain, general health and social functioning dimensions compared to other FGID studies; scores on the other scales are intermediate compared to other studies. Differences with other studies may be at least partially explained by the fact that this is a tertiary care sample, but most studies that are used for comparison are also from referral settings [START_REF] Haag | Is there any association between disturbed gastrointestinal visceromotor and sensory function and impaired quality of life in functional dyspepsia?[END_REF][START_REF] Biggs | Effect of childhood adversity on health related quality of life in patients with upper abdominal or chest pain[END_REF][START_REF] Haag | Is there a benefit from intensified medical and psychological interventions in patients with functional dyspepsia not responding to conventional therapy?[END_REF][START_REF] Wiklund | Does endoscopy have a positive impact on quality of life in dyspepsia?[END_REF][START_REF] Jones | Quality of Life in Patients With Inflammatory Bowel Disease and Irritable Bowel Syndrome Differs Between Subjects Recruited from Clinic or the Internet[END_REF] .

Hypothesis 1 & 2: 'somatization' as a risk factor for impaired physical HRQoL

We were able to confirm the first hypothesis, as we found that 'somatization' is the most important risk factor independently associated with impaired physical HRQoL in FD. This is a novel finding that has, to the best of our knowledge, not been reported in the literature before.

However, the fact that increased experiencing and reporting of somatic symptoms in general (including extra-intestinal symptoms) is a more important risk factor than dyspepsia symptoms alone is well in line with intuition. It also fits with previous findings that 'somatization' is the most important determinant of symptoms as well as comorbidity and treatment response in FGID [START_REF] Van Oudenhove | Determinants of Symptoms in Functional Dyspepsia: Gastric Sensorimotor Function, Psychosocial Factors or Somatization?[END_REF][START_REF] Whitehead | Comorbidity in Irritable Bowel Syndrome[END_REF][START_REF] Creed | The relationship between somatisation and outcome in patients with severe irritable bowel syndrome[END_REF] .

The second hypothesis was also confirmed, as 'somatization' was found to 'mediate' (in its limited sense defined in the methods section) the effect of abuse history and depression on physical HRQoL. This indicates that the effects of abuse history and psychiatric comorbidity on physical HRQoL, which have been found before, may be indirect (i.e. through 'somatization') rather than direct, as suggested in previous studies [START_REF] Biggs | Effect of childhood adversity on health related quality of life in patients with upper abdominal or chest pain[END_REF][START_REF] Haag | Impairment of health-related quality of life in functional dyspepsia and chronic liver disease: the influence of depression and anxiety[END_REF] . The fact that 'somatization', which was the most important risk factor for impaired physical HRQoL in the present study, was not included in previous studies, may also account for the fact that the variance in PCS score explained by our present final model (52%) is considerably higher than previously reported models (ranging from 15% to 40%) [START_REF] Haag | Is there any association between disturbed gastrointestinal visceromotor and sensory function and impaired quality of life in functional dyspepsia?[END_REF][START_REF] Talley | Functional dyspepsia, delayed gastric emptying, and impaired quality of life[END_REF][START_REF] Biggs | Effect of childhood adversity on health related quality of life in patients with upper abdominal or chest pain[END_REF][START_REF] Haag | Impairment of health-related quality of life in functional dyspepsia and chronic liver disease: the influence of depression and anxiety[END_REF] .

An important issue that remains to be elucidated is whether 'somatization' needs to be conceptualized as a primary phenomenon ('functional somatization') or rather as the result of a complex psychobiological process in which psychological factors/processes such as abuse history, hypervigilance, symptom-specific anxiety or negative affect lead to amplification of bodily signals through central sensitization of interoceptive/pain-processing neural systems (secondary phenomenon, 'presenting somatization') [START_REF] De Gucht | Somatization: A Critical Review of Conceptual and Methodological Issues[END_REF][START_REF] De Gucht | Explaining medically unexplained symptoms: Toward a multidimensional, theory-based approach to somatization[END_REF][START_REF] Naliboff | Towards a Nondualistic Approach to Multisystem Illness[END_REF][START_REF] Anand | Peripheral and Central Mechanisms of Visceral Sensitization in Man[END_REF][START_REF] Leserman | Relationship of Abuse History to Functional Gastrointestinal Disorders and Symptoms: Some Possible Mediating Mechanisms[END_REF] . Although the presently used measures conceptualize 'somatization' in a purely descriptive way (i.e. by simply counting 'unexplained' somatic symptoms, corresponding at best with 'functional somatization'), our present finding that 'somatization' may act as a mediator for the effect of abuse history and depression on physical HRQoL provides some further support for the hypothesis that psycho(bio)logical factors may underlie the descriptive phenomenon of 'somatization'.

Although the mechanisms by which 'somatization' 'mediates' the effect of depression and abuse history cannot be derived from the present study, it has recently been shown that both depression and abuse history may interfere with pain-processing systems in the brain [START_REF] Van Oudenhove | Regional brain activity in functional dyspepsia: a H 2 15 O-PET study on the role of gastric sensitivity & abuse history[END_REF][START_REF] Strigo | Association of Major Depressive Disorder With Altered Functional Brain Response During Anticipation and Processing of Heat Pain[END_REF] , which may well lead to increased generalized somatic symptom reporting (i.e. 'somatization').

Hypothesis 3: mental HRQoL is best explained by a combination of psychosocial factors

This hypothesis could also be confirmed and we identified the most important risk factors associated with impaired mental HRQoL in FD. The final model explained 66% of the variance, which is again considerably more than previous studies, probably due to the inclusion of a more extensive set of psychosocial factors (including abuse history, 'trait' and 'state' psychological factors/psychiatric comorbidity). First, abuse history was significantly associated with MCS only before 'trait' psychological factors were controlled for. Moreover, it only explained a small Van Oudenhove et al amount of the variance in MCS (3%). As this may indicate mediation of the effect of abuse by alexithymia or trait anxiety, formal testing of mediation was performed. However, alexithymia did not reduce the effect of abuse to non-significance, which is required for mediation [START_REF] Baron | The moderator-mediator variable distinction in social psychological research: conceptual, strategic, and statistical considerations[END_REF] . Trait anxiety, on the contrary, did reduce the significance of the effect of abuse history on MCS considerably, but its association with abuse history itself, which is also required for mediation, was only borderline significant (p=0.07) (data not shown) [START_REF] Baron | The moderator-mediator variable distinction in social psychological research: conceptual, strategic, and statistical considerations[END_REF] . Therefore, we cannot fully confirm the hypothesis that the effect of abuse on MCS was mediated by either of both 'trait' psychological factors. This is in line with previous findings by Biggs et al, who found a significant effect of abuse on MCS only before "distress" ('state' anxiety and depression') were controlled for [START_REF] Biggs | Effect of childhood adversity on health related quality of life in patients with upper abdominal or chest pain[END_REF] . Second, the association of 'trait' psychological dimensions with MCS was elucidated and these were found to explain an important part of the variance in MCS (42%). Alexithymia has been shown before to play an important role in functional somatic syndromes, including FGID 21, 63, 64 , but we are not aware of any studies on its effect on HRQoL in FD. In the present study, its association with impaired mental HRQoL was borderline significant (p=0.06) in the final model (i.e. after 'state' psychosocial factors were entered). Trait anxiety was found to have a significant direct effect in the final model, even after controlling for 'state' factors. Third, 'state' psychological factors/psychiatric comorbidity explained an additional 21% of the variance. (Lack of) positive affect was the most significant risk factor here, followed by negative affect and comorbid generalized anxiety disorder; depression showed a trend (p=0.06). Positive and negative affect are two independent, distinctive measures of mood [START_REF] Watson | Development and Validation of Brief Measures of Positive and Negative Affect: The PANAS Scales[END_REF] . Positive affect reflects "enthusiasm, activity & energy and alertness", whereas "negative affect is a general dimension of subjective distress and unpleasurable engagement" [START_REF] Watson | Development and Validation of Brief Measures of Positive and Negative Affect: The PANAS Scales[END_REF] . Negative affect has received considerable attention in the literature about functional somatic syndromes, but (lack of) positive affect may be equally important, although relatively neglected [START_REF] De Gucht | Neuroticism, alexithymia, negative affect, and positive affect as determinants of medically unexplained symptoms[END_REF][START_REF] Zautra | Emotions, Stress & Health[END_REF] . Negative and positive affect have indeed been shown to be independently associated with number of medically unexplained symptoms [START_REF] De Gucht | Neuroticism, alexithymia, negative affect, and positive affect as determinants of medically unexplained symptoms[END_REF] , but we are not aware of any studies on the influence of positive affect on HRQoL in FD. These results may indicate that positive affect may be an important additional factor to consider in FGID research, besides various measures of negative affect. Finally, it should be noted that most of these 'state' psychological factors should be considered overlapping rather than independent risk factors for impaired MCS. This is the first study to include gastric sensitivity and accommodation measured by barostat as potential risk factors for impaired HRQoL in FD. Accommodation was not associated with HRQoL, whereas a significant though relatively weak association between gastric discomfort threshold and PCS was found in bivariate analysis. In the multiple regression analysis, gastric sensitivity remained borderline significant (p<0.08) until entering 'somatization' in the last step.

Unlike in the case of abuse and 'somatization', where evidence exists in the literature, it is very hard to speculate on the putative temporal order of things here. However, gastric hypersensitivity may be the manifestation of a more generalized hypersensitivity for (painful) somatic stimuli, which may be one of the key psychobiological mechanisms underlying 'somatization' [START_REF] De Gucht | Explaining medically unexplained symptoms: Toward a multidimensional, theory-based approach to somatization[END_REF][START_REF] Naliboff | Towards a Nondualistic Approach to Multisystem Illness[END_REF][START_REF] Aaron | A Review of the Evidence for Overlap among Unexplained Clinical Conditions[END_REF] . We therefore speculate that gastric sensitivity and 'somatization' may act as proxy risk factors for impaired physical HRQoL; this term does, contrary to "mediator", not contain an assumption on temporal precedence [START_REF] Kraemer | How Do Risk Factors Work Together? Mediators, Moderators, and Independent, Overlapping, and Proxy Risk Factors[END_REF] . In other words, gastric hypersensitivity could be one aspect or manifestation of the multidimensional process of 'somatization'. This is supported by the emerging body of evidence showing a signficant association between psychosocial factors and (gastric) sensory thresholds [START_REF] Van Oudenhove | Limitations of current paradigms for visceral sensitivity testing[END_REF] . In the present study, a significant correlation between gastric discomfort threshold and 'somatization' was indeed found (r=-0.22, p=0.0006).

In bivariate analysis, we also found a significant though weak correlation between gastric emptying and PCS; significance was, however, completely lost in a multiple linear regression model controlling for gender, employment status and gastric discomfort threshold. This is in line with a previous study [START_REF] Talley | Functional dyspepsia, delayed gastric emptying, and impaired quality of life[END_REF] , where gastric emptying was weakly associated with PCS in bivariate analysis, but not in multiple linear regression controlling for age, gender, BMI and dyspepsia symptoms. In another very recent study, gastric emptying was not associated with PCS, although an association between emptying and MCS was found in a pain-predominant subgroup only [START_REF] Haag | Is there any association between disturbed gastrointestinal visceromotor and sensory function and impaired quality of life in functional dyspepsia?[END_REF] . First, we only used self-report measures (i.e. questionnaires that were completed by the participants themselves, without involvement of an interviewer), which may be prone to certain forms of bias. For example, abuse history questionnaires may be prone to recall bias and their results may be confounded by present depressive symptoms [START_REF] Raphael | Childhood abuse and pain in adulthood: more than a modest relationship?[END_REF] . Moreover, abuse history questionnaires may be prone to social desirability reporting bias, although this may be a problem with abuse interview as well. Furthermore, the abuse measures we used are validated specifically in (functional) GI populations with an interview as comparison [START_REF] Leserman | The reliability and validity of a sexual and physical abuse history questionnaire in female patients with gastrointestinal disorders[END_REF] and have been widely used. The specific problems regarding the self-report measures of 'somatization' and CF comorbidity have already been adressed in the methods section. Although a structured clinical interview remains the 'gold standard' for diagnosing psychiatric comorbidity, we chose selfreport measures that have been validated with a structured interview as a comparison, although not always in (functional) GI populations.

Limitations of the study

Second, this is a cross-sectional study, permitting conclusions about associations but not about causality, temporal order of directionality of the relationships between the variables. For example, the order in which (groups of) variables were entered in the regression models was chosen to reflect the putative temporal order of things in the best way possible (based on conceptual as well as empirical grounds), but this remains an assumption. Strictly speaking, mediation requires temporal precedence of the mediator by the mediated variable [START_REF] Kraemer | How Do Risk Factors Work Together? Mediators, Moderators, and Independent, Overlapping, and Proxy Risk Factors[END_REF] . Although this cannot be determined here, it is conceivable and has been shown before that abuse precedes the onset of 'somatization' [START_REF] Leserman | Relationship of Abuse History to Functional Gastrointestinal Disorders and Symptoms: Some Possible Mediating Mechanisms[END_REF][START_REF] Salmon | Abuse, Dissociation, and Somatization in Irritable Bowel Syndrome: Towards an Explanatory Model[END_REF] and that a stable personality trait as alexithymia precedes and predicts the onset of 'state' depression [START_REF] Conrad | Alexithymia, temperament and character as predictors of psychopathology in patients with major depression[END_REF] . We therefore used the term 'mediation' is a more limited sense (i.e. devoid of its temporal precedence aspect) throughout this paper. However, these results, especially on 'mediation', should be interpreted with sufficient caution and require replication in longitudinal studies before any definite conclusions can be drawn. Third, the patient population consists of tertiary care FD patients, limiting generalizability of the results towards other populations of FD patients. As patients were recruited consecutively, they reflect the average tertiary care FD patients and were therefore heterogeneous in terms of onset and course of illness, psychiatric comorbidity, previous medication use, etc. Fourth, we only used a generic and not a disease-specific measure of HRQoL and we did not include a positive or negative control group, as a consequence of which we cannot determine whether these findings are specific for FD. However, the generic HRQoL instrument we used has been widely used and the use of norm-based scoring allows reliable comparison with other studies.

Conclusion

We presented the first study in FD to investigate a comprehensive set of potential risk factors for impaired generic HRQoL, including gastric sensorimotor function, psychosocial factors/psychiatric comorbidity and 'somatization', from which we can conclude the following.

First, 'somatization' is the most important risk factor associated with impairment in the physical domain of HRQoL. Second, abuse history and depression are also associated with physical HRQoL, but their effect is indirect, i.e. mediated by 'somatization'. Third, impaired mental HRQoL in FD is best explained by a combination of overlapping psychosocial factors, of which (lack of) positive affect is the most important one, besides other state and trait factors that are related to negative affectivity (trait anxiety, present negative affect, comorbid generalized anxiety disorder). Fourth, gastric sensorimotor function is not significantly associated with impaired HRQoL when 'somatization' is controlled for, but we may speculate that gastric hypersensitivity is the manifestation of a more generalized hypersensitivity for somatic stimuli, which is a psychobiological process that may underlie the descriptive concept of 'somatization'.

We believe the most important clinical "take home message" from this study is that, if we want to obtain a realistic picture of the QoL of FD patients, we need not to focus narrowly on gastric mechanisms and symptoms, but adopt a broader view including psychosocial factors and (extraintestinal) somatic symptoms.

STATEMENT OF INTERESTS

TABLES

  . The putative influence of gastric sensitivity or gastric accommodation (meal-induced gastric relaxation) on QoL has not been studied either. The general aim of the present study is to determine the relative contribution of gastric sensorimotor function, psychosocial factors & 'somatization'/somatic symptom reporting to HRQoL in FD. More specifically, we wanted to test the following hypotheses. First, 'somatization' is the most important risk factor for impairment in the physical domain of HRQoL in FD. Second, 'somatization' 'mediates' the influence of psychosocial factors on impairment in the physical domain of HRQoL in FD. Third, impaired mental HRQoL in FD is best explained by a combination of various psychosocial factors (abuse history, psychological traits, current psychological state and/or psychiatric comorbidity). Fourth, gastric sensorimotor function is not a significant risk factor for impaired HRQoL when psychosocial factors and 'somatization' are controlled for. speaking patients recently diagnosed with FD (either at their visit to our tertiary care clinic or at a recent secondary care gastroenterologist visit that lead to referral to our centre) were recruited between January 2002 & February 2009. The patient sample of the present study does partially overlap with the study population from our recent studies on the relationship between anxiety and gastric sensorimotor function as well as on determinants of symptoms in FD

  .

  or well-being. Norm-based scores can be calculated for each scale based on 1998 US population norms, with the population norm for all scale scores being 50 and a low score indicating poor health; a score of 40 represents one standard deviation below the norm[START_REF] Ware | SF-36 Physical & Mental Health Summary Scales: A Manual for Users of Version 1[END_REF] . Scoring based on US

  Van Oudenhove et al comorbidity/psychological factors (depression, panic disorder, generalized anxiety disorder, positive and negative affect).

DISCUSSION

  To the best of our knowledge, this is the first study in FD to investigate a comprehensive set of potential risk factors for impaired HRQoL, including gastric sensorimotor function, psychosocial factors/psychiatric comorbidity and 'somatization'.

Hypothesis 4 :

 4 gastric sensorimotor function is not a significant risk factor for impaired HRQoL when psychosocial factors and 'somatization' are controlled for

  Van Oudenhove et alThis study was funded by a grant from the Research Foundation -Flanders (FWO-Vlaanderen) to Prof. Tack. Lukas Van Oudenhove is a postdoctoral research fellow of the Research Foundation -Flanders (FWO-Vlaanderen).

Figure 1 Patient participation flowchart Figure 2

 12 Figure 1

Figure 3 a

 3 Figure 3

  8 individual SF-36 scales were 46.1±10.1 (physical functioning), 39.8±11.7 (role limitations physical), 38.2±9.8 (bodily), 38.1±9.0 (general health), 46.3±8.8 (vitality), 38.2±11.5 (social functioning), 46.3±12.8 (role limitations emotional) and 44.4±10.8 (mental health). This resulted in mean composite scores of 40.2±9.5 (PCS) and 45.1±10.8 (MCS). The scores from the present study are compared with US

Table 1

 1 Significant bivariate associations of SF-36 Physical and Mental Composite Scores with sociodemographic, gastric sensorimotor, psychosocial and somatic symptom variables : only available in a subset of patients, not used in multiple regression analysis; ρ=Spearman's rho correlation coefficient; χ²-values from Kruskal-Wallis test

	variable	ρ	χ²	p
	Physical Composite Score
	sociodemographics
	gender		6.9	0.009
	employment status		44.9	<0.0001
	gastric sensorimotor function
	discomfort threshold	0.20		0.002
	emptying*	-0.23		0.004
	abuse history
	overall adult abuse		8.8	0.003
	'state' psychosocial
	depression	-0.36		<0.0001
	positive affect	0.22		0.0006
	somatic symptoms
	dyspepsia symptoms	-0.31		<0.0001
	weight loss	-0.35		<0.0001
	chronic fatigue		51.6	<0.0001
	'somatization'	-0.50		<0.0001
	Mental Composite Score
	abuse history
	overall lifetime abuse		6.4	0.01
	'trait' psychosocial
	alexithymia	-0.42		<0.0001
	trait anxiety	-0.64		<0.0001
	'state' psychosocial
	depression	-0.54		<0.0001
	panic disorder		15	0.0001
	generalized anxiety disorder		38.9	<0.0001
	positive affect	0.56		<0.0001
	negative affect	-0.62		<0.0001

*

Table 2

 2 Hierarchical multiple linear regression model with SF-36 Physical Composite Score as the dependent variable

	variable	β/F variable	B variable	p variable	η² variable	R² model
	step 0: sociodemographics
	gender*	-1.77±1.49		0.24	0.006	0.21
	employment status	F=9.18		<0.0001	0.180
	step 1: gastric sensorimotor function
	gender	-1.66±1.53		0.28	0.005	0.23
	employment status	F=8.0		<0.0001	0.154
	discomfort threshold	0.31±0.17	0.12	0.07	0.013
	step 2: abuse history
	gender*	-1.88±1.73		0.28	0.008	0.26
	employment status	F=4.34		0.001	0.123
	discomfort threshold	0.35±0.20	0.13	0.08	0.019
	overall adult abuse history° -5.29±1.98		0.008	0.044
	step 3: 'state' psychosocial
	gender*	-1.87±1.70		0.27	0.008	0.29
	employment status	F=3.71		0.003	0.111
	discomfort threshold	0.37±0.20	0.14	0.06	0.024
	overall adult abuse°	-3.80±1.99		0.06	0.024
	depression	-0.30±0.15	-0.17	0.04	0.028
	positive affect	0.03±0.10	0.02	0.81	0.004
	step 4: somatic symptoms
	gender*	-2.28±1.50		0.13	0.018	0.52
	employment status	F=2.22		0.06	0.082
	discomfort threshold	0.26±0.19	0.10	0.16	0.016
	overall adult abuse°	-1.50±1.80		0.40	0.006
	depression	0.10±0.14	0.05	0.48	0.004
	positive affect	0.03±0.09	0.02	0.79	0.001
	dyspepsia symptoms	-0.26±0.14	-0.13	0.07	0.025
	weight loss	0.004±0.08	0.003	0.96	0.000
	chronic fatigue^	-4.26±1.34		0.002	0.075
	'somatization'	-0.77±0.18	-0.36	<0.0001	0.125
	all models p<0.0001; *: reference category=men; °: reference category=no abuse; ^:reference
	category=no chronic fatigue
	η² variable : squared full partial correlation, calculated based on type III sum of squares

Table 3

 3 Hierarchical multiple linear regression model with SF-36 Mental Composite Score as the dependent variable

	variable	β±SE variable	B variable	p variable	η² variable	R² model
	step 1: abuse history
	overall lifetime abuse°	-4.2±1.8		0.014	0.030	0.030
	step 2: 'trait' psychosocial
	overall lifetime abuse°	-2.06±1.41		0.15	0.013	0.45
	alexithymia	-0.23±0.06	-0.26	<0.0001	0.089
	trait anxiety	-0.46±0.06	-0.49	<0.0001	0.245
	step 3: 'state' psychosocial
	overall lifetime abuse°	-1.79±1.15		0.12	0.015	0.66
	alexithymia	-0.09±0.05	-0.10	0.06	0.022
	trait anxiety	-0.14±0.06	-0.15	0.02	0.034
	depression	-0.26±0.14	-0.13	0.06	0.022
	panic disorder *	1.39±1.59		0.38	0.005
	generalized anxiety disorder^	-5.51±2.15		0.01	0.040
	positive affect	0.45±0.09	0.30	<0.0001	0.142
	negative affect	-0.34±0.11	-0.24	0.002	0.060
	all models p<0.0001; °: reference category=no abuse; *: reference category=no panic disorder; ^:
	reference category=no anxiety disorder
	η² variable : squared full partial correlation, calculated based on type III sum of squares

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