Philippe Gautret
email: philippe.gautret@club-internet.fr

Marta Diaz-Menendez

Abraham Goorhuis

Ryan M Wallace

Veerle Msimang

Jesse Blanton

Laurent Dacheux

Perrine Parize

Lucille Blumberg

Hervé Bourhy

Martin P Grobusch

Epidemiology of rabies cases among international travellers, 2013-2019: A retrospective analysis of published reports

Keywords: Rabies, Traveller, Imported, Epidemiology, Diagnosis

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Rabies in international travellers is a rare but dramatic deadly event that usually leads to case reporting in the medical literature [START_REF] Malerczyk | Imported human rabies cases in europe, the United States, and Japan, 1990 to 2010[END_REF] and frequently receives media attention. A previous review for the period 1990-2012 using the PubMed and Scopus search engines, and reviewing ProMED-mail, revealed 60 cases of travel-associated rabies (2-3 cases per year) worldwide [START_REF] Carrara | Imported human rabies cases worldwide, 1990-2012[END_REF]. Most cases were diagnosed in Europe and in the United States of America (USA). Most exposures occurred in Asia (24/40; 40%), notably in India and the Philippines; in Central America and the Caribbean (9/60, 15%); and in North Africa (6/60, 10%). A significant proportion of cases occurred in migrants or their descendants (26/60; 43%). They were infected in their origin country prior to migration (7/26; 27%), or infected during a trip to their origin country for the purpose of visiting friends and relatives (14/26; 54%), or for other reasons (5/26; 19%), whilst the remaining cases were in individuals travelling for tourism, business or expatriation (34/60; 57%). Travel duration was not documented in the majority of the reports. Two cases were recorded in tourists taking two-week trips to India and Kenya. A predominance of male patients was observed (45/60; 75%) and the proportion of adults was high (50/57; 88%). Dogs were involved in most cases (51/55; 93%), bats in three cases and a fox in one case. In half of the cases, the diagnosis was challenging, with multiple missed diagnoses and transfers from specialty to specialty before the diagnosis of rabies was confirmed. In one-third of the cases a confirmed diagnosis of rabies was obtained only post-mortem. This was mostly due to a low index of suspicion for rabies from physicians lacking familiarity with the disease, a negative history of animal bites or exposure to rabies, and atypical clinical presentation of the disease.

We present here an update of rabies cases in international travellers from 2013 to 2019.

Materials and Methods

We retrieved information on human rabies cases in travellers using PubMed (MEDLINE) and Scopus databases (http://www.ncbi.nlm.nih.gov/pubmed; www.scopus.com/scopus/home.url), from January 2013 to December 2019, cross-referencing the following terms: 'rabies', 'imported' and 'travel'. Additionally, we searched the two databases for all rabies case reports and checked for possible travel association. The reference lists of the systematic reviews and other identified papers were scanned for potentially relevant primary studies that could be considered for inclusion in the review. Additional searches were conducted using the ProMED-mail (http://www.promedmail.org/) and Google (http://www.google.fr/) general search engine. Finally, the GeoSentinel/EuroTravNet (https://www.istm.org/geosentinelhttps://www.istm.org/eurotravnet) database was queried for potentially relevant cases.

The inclusion criteria were all available publications written in English, French and Spanish languages on human rabies cases in individuals who crossed an international border between the time of infection and diagnosis or who were infected following expatriation or migration.

Reports with insufficient clinical descriptions were only included in the epidemiological analyses. When possible, corresponding authors of case reports and public health representatives were queried for missing information. We used WHO guide as a standard for rabies prophylaxis (https://www.who.int/rabies/PEP_Prophylaxis_guideline_15_12_2014.pdf).

Results

Epidemiology (Tables 1,2)

A total of 23 cases meeting the inclusion criteria were identified from 2013 through 2019 , an average of three cases per year over the seven-year study period, with a maximum of six cases in 2014. One 2019 case in a Latvian citizen, where country of acquisition was unascertainable (Latvia or India) was excluded. The mean age of patients was 36 years (range, 4-65 years). Three cases were reported in children, including a 12 year-old Yemeni refugee who was infected in Saudi Arabia [START_REF] Dhayhi | First confirmed case of local human rabies in Saudi Arabia[END_REF], a 10 year-old French tourist child infected in Sri-Lanka and a 3 year-old Zimbabwean migrant to South-Africa, infected in Zimbabwe [START_REF]An update on rabies in South Africa, 2017[END_REF]. The male-to-female ratio was 2.8. Most cases were diagnosed in Europe (10/23, 44%), notably in France (3 cases), in The Netherlands (2 cases) and in Spain (2 cases), and the Middle East (6/23, 26%); notably in Saudi Arabia (2 cases) and in Qatar (2 cases). Migrants originating from rabies-endemic low-and-middle income countries and their descendants accounted for 61% (14/21) of cases, following initial migration trips (8 cases) or when visiting friends and relatives in their country of origin (6 cases). Other individuals were from developed countries and acquired rabies when travelling for tourism (6 cases), business (2 cases), and expatriation (1 case). Most exposures occurred in Asia (13/23, 57%) (Figure 1), notably in India (5 cases) and Philippines (3 cases), or in Africa (7/23, 30%), notably in Morocco (4 cases).

Additionally, there were two cases with exposure in Central America and one in Saudi Arabia. Travel duration (excluding migration trip) was documented in 9/15 cases. Median travel duration was 60 days (range from 7-240 days). Of note, a Dutch citizen travelled for one week, in Haiti for business purpose [START_REF]ProMED-mail post. Rabies -Netherlands ex Haiti, canine exposure, human[END_REF] and a Saudi citizen travelled for 12 days in Morocco for tourism [START_REF] Alknawy | First confirmed case of human rabies in Saudi Arabia[END_REF]. A history of an animal bite or scratch was reported in 20/23 cases and involved dogs in 17 cases; with two cases resulting from cat bites in Morocco and one case resulting from the bite of a raccoon-like animal in Nepal. In three patients, no animalrelated injury was reported, but one patient owned a dog in Guatemala, which died of unknown cause [START_REF] Wallace | Rabies death attributed to exposure in Central America with symptom onset in a U.S. detention facility -Texas, 2013[END_REF], and another patient had stray dogs in his residency area. In a case from Mali, phylogenetic analysis based on the full-length viral nucleoprotein nucleotide sequence indicated that the virus isolate belonged to the Africa 2 phyloclade within the Rabies lyssavirus (RABV) species, which is known to circulate dogs in West Africa [START_REF] Contou | Severe ketoalkalosis as initial presentation of imported human rabies in France[END_REF].

Four secondary cases (not travel-associated) were observed in transplant recipients from Kuwait and Saudi Arabia who received organs (heart, liver, kidneys) from an Indian migrant worker donor diseased in Kuwait. Additionally, two cornea recipients from the same donor underwent explantation and survived [START_REF] Al-Fadhli | Case Report 2 :Rabies Through Organ Transplant[END_REF][START_REF] Elsiesy | Donor transmited rabies outbreak involving four transplant recepients in Kuwait and Saudi Arabia[END_REF].

Clinical features and biological confirmation of rabies

The incubation time was documented in 19/23 cases (Figure 2) with a mean incubation time of 87.6 days (median time: 56 days, range, 30-420). The longest incubation time was about 14 months in a Czech patient who sustained a dog bite in Bangladesh while travelling for tourism and developed rabies disease during a stay in France. In 14 reports, the clinical description was adequate to allow classification of the disease. Thirteen cases were furious rabies and one paralytic. Hydrophobia was reported in 7 cases, hypersalivation in 5 cases and aerophobia in 3 cases.

Atypical presentations included a case of severe alkalosis due to hyperventilation with ketonuria and hyperglycemia, as initial presentation [START_REF] Contou | Severe ketoalkalosis as initial presentation of imported human rabies in France[END_REF]. Another patient presented with an acute myocarditis (a common feature in rabies) but with electrocardiogram changes (ST elevation) initially interpreted as suggestive for myocardial infarction [START_REF] Park | Rabies Encephalitis With Myocarditis Mimicking ST-Elevation Myocardial Infarction[END_REF]. One patient was initially misdiagnosed with sepsis [START_REF] Chacko | Diagnostic difficulties in human rabies: A case report and review of the literature[END_REF]. One patient presented with a pneumomediastinum [START_REF] Wallace | Rabies death attributed to exposure in Central America with symptom onset in a U.S. detention facility -Texas, 2013[END_REF], and the single paralytic case was initially misdiagnosed as Guillain-Barré syndrome [START_REF] Cohen | Paralytic rabies misdiagnosed as Guillain-Barre syndrome in a guest worker: A case report[END_REF]. In the majority of cases with available information, diagnosis was made by PCR on skin biopsy or saliva and CSF. Unfortunately, information about the variant types of lyssavirus was lacking in most reports.

In 17 patients (74%), no rabies post-exposure prophylaxis (RPEP) was administered before rabies symptoms appeared. In two cases, no RPEP was mentioned. The remaining four cases reportedly received incomplete RPEP series. One patient from the Netherlands had supposedly received four doses of vaccine in India the next day after sustaining a transdermal bite in her hand, but proof of vaccination was lacking and the vaccination schedule was deviant from any international RPEP guideline (4 vaccinations in a time period of 2 weeks).

Possibly, counterfeit vaccine was administered [START_REF] Taylor | Avoiding preventable deaths: The scourge of counterfeit rabies vaccines[END_REF], given the fact that serum antibodies against rabies virus were low (<0.5 IU/ml), measured at diagnosis, eight weeks later. This patient did not receive rabies immune globulin (RIG) and developed rabies symptoms eight weeks after exposure [START_REF]ProMED-mail post. Rabies -Netherlands ex India (Tamil Nadu), canine, human[END_REF]. The French patient expatriated to Cambodia received one dose of a vaccine following a transdermal bite in her hand, according to a witness, (could not identify whether that one dose was rabies or tetanus vaccine) but no RIG in Cambodia, and developed rabies eight months later [START_REF] Tarantola | A confirmed rabies case in a French resident in Cambodia, June 2015[END_REF]. The Zimbabwean patient received one dose of confirmed rabies vaccine in Zimbabwe and another in Tanzania following a transdermal bite in his neck but no RIG, according to family and developed rabies 79 days later. Finally, the Italian patient received rabies vaccines in Tanzania (number of doses not documented in the report) but no RIG and developed rabies one month later [START_REF]ProMED-mail post. Rabies -Italy (AP) ex Tanzania (Zanzibar) human, immunocompromised[END_REF]. The type of injury was not described in this last case. Information about treatment in symptomatic patients was missing in most cases; however, a treatment attempt based on the Milwaukee protocol [START_REF] Zeiler | Critical appraisal of the Milwaukee protocol for rabies: this failed approach should be abandoned[END_REF] (or derived from), that includes therapeutic coma, ketamine infusion, amantadine, and the screening/prophylaxis/management of cerebral vasospasm was conducted in six patients [START_REF] Wallace | Rabies death attributed to exposure in Central America with symptom onset in a U.S. detention facility -Texas, 2013[END_REF][START_REF] Cohen | Paralytic rabies misdiagnosed as Guillain-Barre syndrome in a guest worker: A case report[END_REF][START_REF] Chacko | Diagnostic difficulties in human rabies: A case report and review of the literature[END_REF][START_REF] Elsiesy | Donor transmited rabies outbreak involving four transplant recepients in Kuwait and Saudi Arabia[END_REF][START_REF] Dhayhi | First confirmed case of local human rabies in Saudi Arabia[END_REF][START_REF] Murphy | Human Rabies -Virginia, 2017[END_REF]. All 23 patients died.

Discussion

This update shows that rabies cases among travellers continue to occur with no significant change as compared to the period 1990-2012 regarding the absolute number of cases.

Although likely underestimating the true burden of rabies among international travellers and migrants, notably in patients travelling between developing countries, this figure of three cases per year stands in marked contrast with the estimated 0.4% per-month incidence of animal bites requiring RPEP in international travellers that was calculated from prospective cohort survey data conducted among travellers enrolled prior departure and questioned on return [START_REF] Gautret | Rabies vaccination for international travelers[END_REF]. Risk factors cannot be extrapolated from our results because we lack denominators. Of note, only three patients definitely received some fraction of RPEP of whom one only had received a complete course of vaccine, and none had received RIG. RPEP might be difficult to obtain in some countries during travel, notably RIG and in the event that it is obtained, it can be counterfeit [START_REF] Taylor | Avoiding preventable deaths: The scourge of counterfeit rabies vaccines[END_REF]. In a recent GeoSentinel survey, about two-thirds of travellers with an indication for RIG who started RPEP while travelling did not receive RIG [START_REF] Gautret | Rabies post-exposure prophylaxis started during or after travel: A GeoSentinel analysis[END_REF]. The death of the three patients in our series is not indicative of failure of RPEP since vaccine courses were incomplete and RIG was missing despite being indicated due to the nature of injuries in at least two cases.

Similar to the previous period of 1990-2012, a predominance of adults and male patients was observed in travellers with rabies. Unlike in populations living in rabies-endemic countries where children < 15years represent a large portion of human rabies cases (40-50%) [30], children were under-represented in this study (8%) as well as in the previous one (11%) [START_REF] Carrara | Imported human rabies cases worldwide, 1990-2012[END_REF]. This correlates with data on potentially rabid animal exposure in travellers seeking care for RPEP, as observed in a large GeoSentinel survey where children under 15 years accounted for 11% of patients [START_REF] Gautret | Animalassociated exposure to rabies virus among travelers, 1997-2012[END_REF]. This may be due to the age profile of travellers which is different from the age profile in those countries were rabies is most highly endemic. By contrast, the predominance of male patients with rabies (74%), in our study and in the previous one (75%) [START_REF] Carrara | Imported human rabies cases worldwide, 1990-2012[END_REF], does not correlate with the 51% male patient proportion observed in the GeoSentinel survey on travellers seeking care for RPEP [START_REF] Gautret | Animalassociated exposure to rabies virus among travelers, 1997-2012[END_REF]. Europe remained the commonest region where cases are diagnosed which is likely reflecting both the quality of rabies surveillance and the large numbers of tourists and migrants from and to Europe. The Middle-East region emerged as second with reports from Qatar, Kuwait, Saudi Arabia and Israel. Of note, there was no recent case acquired in Mexico, a country from which 5 cases were acquired between 1990-2012, with the last one in 2010 [START_REF] Carrara | Imported human rabies cases worldwide, 1990-2012[END_REF]. This might be chance, but most likely rather reflects the success of Mexico's canine rabies elimination efforts and their newly recognised status by the World Health Organization as "free from dog-mediated human rabies deaths" [START_REF] Ma | Public Veterinary Medicine: Public Health: Rabies surveillance in the United States during 2018[END_REF].

Migrants from low-income countries accounted for most of the recent cases; in contrast with the previous data from 1990-2012, where travellers from high-income countries accounted for the majority of cases. This may be possibly due to increased rabies prevention among travellers. India, the Philippines and Morocco continue to be the top countries for exposure. In a GeoSentinel study about patients receiving RPEP, most exposures occurred in Asia (74%) with top countries being Thailand, Indonesia, Nepal, China and India, and only 5% in North Africa [START_REF] Gautret | Animalassociated exposure to rabies virus among travelers, 1997-2012[END_REF]. New countries of acquisition emerged, including Saudi Arabia, Indonesia, Cambodia, Zimbabwe, Tanzania (Zanzibar) and Guatemala (Figure 1). As observed previously [START_REF] Carrara | Imported human rabies cases worldwide, 1990-2012[END_REF], the diagnosis was challenging in some cases, because of atypical presentation and because a history of animal bite or exposure to rabies was lacking. In one migrant from India to Kuwait, the diagnosis was missed, resulting in subsequent cases in four organ recipients [START_REF] Al-Fadhli | Case Report 2 :Rabies Through Organ Transplant[END_REF][START_REF] Elsiesy | Donor transmited rabies outbreak involving four transplant recepients in Kuwait and Saudi Arabia[END_REF]. A similar scenario occurred in Germany in 2005, with three cases of rabies in patients who received transplants from a donor that was retrospectively diagnosed with rabies resulting from a dog bite in India that was not known at the time he died [START_REF] Maier | Management and outcomes after multiple corneal and solid organ transplantations from a donor infected with rabies virus[END_REF]. This suggests that history of animal bites in a rabies endemic country should be queried before donation.

Understandably, physicians in countries where rabies has been eliminated many years ago are not familiar with rabies symptoms. A history of an animal bite is frequently missing, incubation time may be long and symptoms may be atypical. Despite the rarity of human rabies deaths in many high-income countries, rabies should be suspected in any patient with encephalitis or paralysis who travelled to or migrated from a rabies endemic country [START_REF] Carrara | Imported human rabies cases worldwide, 1990-2012[END_REF].

Comprehensive information about a rabies risk should be given to travellers to rabies endemic countries, notably migrants visiting friends and relatives. As it conveys life-long boostability, pre-travel vaccination which has been recently simplified from three doses over one month to two doses over one week [START_REF] Health Organization | Rabies vaccines: WHO position paper -April 2018[END_REF] should be considered, and not only to long-term travelers since the median duration of travel was 15 days in patients seeking care for RPEP after travel and 20 days in those seeking care during travel, in the GeoSentinel survey [START_REF] Gautret | Animalassociated exposure to rabies virus among travelers, 1997-2012[END_REF] and the median time between departure from home and occurrence of exposure to a potentially rabid animal was nine days in a Dutch study conducted among patients seeking care for RPEP on return to the Netherlands [START_REF] Wieten | Risk of rabies exposure among travelers[END_REF]. This shortened rabies pre-travel vaccination two-dose schedule, and the use of the intra-dermal route that allows reducing the amount of compound needed [START_REF] Pijper | Rabies antibody response after two intradermal pre-exposure prophylaxis immunizations: An observational cohort study[END_REF] makes pre-travel vaccination easier and cheaper [START_REF] Pijper | WHO bites back rabies pre-travel vaccination schedules -Implications for travel medicine[END_REF][START_REF] Gautret | One-week, two-visit, double-dose, intra-dermal (22ID) rabies vaccination schedule for travelers: Time/dose sparing, effective but "off label[END_REF]. Easier access to rabies pre-travel vaccination is of major importance given that animal exposure in international travelers can happen anywhere on almost any continents, including in countries endemic for rabies as recently demonstrated in an updated GeoSentinel survey [START_REF] Muehlenbein | Traveler Exposures to Animals: A GeoSentinel Analysis. Traveler Exposures to Animals: A GeoSentinel Analysis[END_REF].

Acknowledgements.

Figure 1 .

 1 Figure 1. Country of exposure in 83 travel-associated rabies cases (black numbers: 1990-

Figure 2 .

 2 Figure 2. Incubation time (19 human rabies cases in travellers (2013-2019). Logarithmic

Table 1 .

 1 Characteristics of 23 travel-associated rabies cases (2013-2019) and National Referral Unit for Tropical and Travel Medicine, Hospital Universitario La Paz-Carlos III, Madrid, Spain (unpublished data) **Centre National de Référence de la Rage, Institut Pasteur, Paris, France (unpublished data)

	Case	Year	Country of	Country where	Country of	History of	RPEP before	Gender, age	Reason for	Travel	Incubation	Clinical symptoms	Positive samples for	Lyssavirus	References
			exposure	the diagnosis was	origin	animal	symptoms	(years)	travel	duration	period		rabies virus (PCR	species
				established		exposure							and or culture) or
													antibodies
	1	2013	Haiti	The Netherlands	The	Dog bite	No	Male, 52	Business	1 weeks	34 days	Fever, headaches, malaise,	Skin biopsy, CSF,	Rabies lyssavirus	[3]
					Netherlands							arm, shoulder and trunk	saliva (virus)	(RABV)
												pain and dysaesthesia,
												hydrophobia
	2	2013	Philippines	Taiwan	Philippines	Dog bite	No	Male, 31	Migration	Not applicable	55 days	Hand pain, nausea,	Not described	-	[4]
									(worker)			vomiting, anorexia, sore
												throat, fever, conscious
												disturbance, fatigue,
												unsteady gait and hand
												twitches, slurred speech
	3	2013	Guatemala	US, Texas	Guatemala	None	No	Male, 28	Migration	Not applicable	Not	Insomnia, anxiety, nausea,	Skin, brain, saliva	Rabies lyssavirus	[5]
						reported			(illegal)		ascertainable	dysphagia, hypersalivation	(virus) and Serum,	(RABV)
						(owed a dog						and expectoration, agitation,	CSF (antibodies)
						in Guatemala						tachycardia, chest
						which died						pneumomediastinum, fever,
						from						aerophobia
						unknown
						cause in 2011
	4	2014	Indonesia	China (Hong	Indonesia	Dog bite	None reported	Male, 28	Business	Not	About 2 months	Back and loin pain, fever,	Brain (virus)	Not documented	[6]
				Kong)						documented		vomiting, walking
												difficulties
	5	2014	Mali	France	Mali	None	No	Male, 57	VFR	6 months	Not	Fever, sweating,	Skin, saliva,	Rabies lyssavirus	[7]
						reported					ascertainable (2	generalized pain, anxiety,	bronchial secretions	(RABV)
						(stray dogs in					weeks to 6	tachypnea, hyperactivity,	(virus) and serum
						his residency					months)	disorientation, delirium,	(antibodies)
						area)						periods of drowsiness,
												hypersalivation, evolution
												toward rapidly extensive
												flaccid and non-reflexive
												tetraparesis
	6	2014	India	The Netherlands	India	Dog bite	Yes (4 rabies	Female, 35	Migration	Not applicable	8 weeks	Hand, arm and neck pain,	Skin, CSF, saliva	Rabies lyssavirus	[8]
							vaccine injections		(married a			hydrophobia, aerophobia,	(virus)	(RABV)
							in India, no RIG)		Dutch			anxiety
									citizen)
	7	2014	Morocco	Spain	Morocco	Dog bite	No	Female, 46	VFR	4 months	7 months	Fever, foot pain and	Skin, saliva (virus)	Not documented	[9]*
												paresthesia, anxiety,
												dysphagia for liquids,
												delirium
	8	2014	India	Israel	India	None	None reported	Female, 32	Migration	Not applicable	Not	Emotional instability,	Skin, saliva (virus)	Rabies lyssavirus	[10]
						reported			(worker)		ascertainable	anxiety, agitation, sore		(RABV)
												throat, abdominal pain,
												vomiting, diarrhea, leg
												weakness, fever, diffuse
												muscle pain, dizziness, back
												and neck pain, tachycardia,
												dyspnea, generalised
												areflexia and hypotonia,
												trismus, evolution toward
												paralysis of the four limbs.
	9	2014	India	Qatar	India	Dog bite	No	Male, 26	VFR	Not	1 month	Dyspnea, tight pain,	Only CSF antibodies
										documented		dysuria, anxiety,	were search and
												tachycardia, tachypnea,	resulted negative.
													Diagnostic was
													based on clinic and
													epidemiological
													context

****and GeoSentinel (unpublished data)

We thank Moataz Al-Knawy, Kristina Angelo, Vanessa Field, David Hamer, Mogens Jensenius, Paola de Benedictis for their support.

Days between exposure and onset of symptoms


Hajer Hadiji
email: hejer.hadiji@enis.tn

Mustapha Assarar

Wajdi Zouari

Floran Pierre

Karim Behlouli

Bassem Zouari

Rezak Ayad

Damping analysis of nonwoven natural fibre-reinforced polypropylene composites used in automotive interior parts

Keywords: Nonwoven, natural fibres, porosity, free vibrations, damping

The aim of this work is to evaluate the dynamic properties of nonwoven flax, hemp, kenaf and glass fibre-reinforced polypropylene (PP) composites. Also, the influence of some parameters, such as the type of reinforcement, the fibre/matrix weight ratio, the fibre orientation and the porosity content, on the damping behaviour of these nonwoven composites is investigated. To this end, a free flexural vibrations analysis was conducted to experimentally identify their natural frequencies and their associated loss factors. The obtained results show that the nonwoven composites reinforced by natural fibres present higher loss factors compared with those of the glass-PP composite. These interesting damping properties make these nonwoven composites very attractive for automotive applications where the dissipation of vibrations is highly requested.

Introduction

The use of natural fibres as reinforcement of composite materials has been proven to be an interesting alternative to synthetic fibres, especially for car interior components in automotive industry [START_REF] Alves | Ecodesign of automotive components making use of natural jute fiber composites[END_REF][START_REF] Khalfallah | Innovative flax tapes reinforced Acrodur biocomposites: A new alternative for automotive applications[END_REF][START_REF] Mueller | New discovery in the properties of composites reinforced with natural fibers[END_REF]. The increasing interest in natural fibres in such applications is motivated by their various advantages. Indeed, composites based on natural fibres are more recyclable than those reinforced with glass or carbon fibres. Also, they have a limited impact on the environment, which could contribute to a healthy ecosystem [START_REF] Bourmaud | Investigations on the recycling of hemp and sisal fibre reinforced polypropylene composites[END_REF][START_REF] Poilâne | Polymer reinforced by flax fibres as a viscoelastoplastic material[END_REF][START_REF] Kern | Mechanical behavior of microcellular, natural fiber reinforced composites at various strain rates and temperatures[END_REF][START_REF] Chegdani | Mechanics of material removal when cutting natural fiber reinforced thermoplastic composites[END_REF][START_REF] Bhingare | A review on natural and waste material composite as acoustic material[END_REF][START_REF] Caprino | Low impact behaviour of hemp fibre reinforced epoxy composites[END_REF][START_REF] Bourmaud | Recycling of L-Poly-(lactide)-Poly-(butylene-succinate)-flax biocomposite[END_REF]. Moreover, their lightweight combined with their interesting specific mechanical properties increase their use in automotive components as an alternative to glass fibres [START_REF] Joshi | Are natural fiber composites environmentally superior to glass fiber reinforced composites?[END_REF][START_REF] Rao | Extraction and tensile properties of natural fibers: Vakka, date and bamboo[END_REF][START_REF] Wambua | Natural fibres: can they replace glass in fibre reinforced plastics?[END_REF][START_REF] Lefeuvre | Tensile properties of elementary fibres of flax and glass: Analysis of reproducibility and scattering[END_REF][START_REF] Van De Velde | Thermoplastic polymers: overview of several properties and their consequences in flax fibre reinforced composites[END_REF].

In parallel with the development of eco-friendly composites, there has been an increasing use of natural fibres as reinforcement in nonwoven composites for automotive interior parts [START_REF] Thilagavathi | Development of natural fiber nonwovens for application as car interiors for noise control[END_REF][START_REF] Parikh | Reducing Automotive Interior Noise with Natural Fiber Nonwoven Floor Covering Systems[END_REF][START_REF] Gu | Physical Properties of Eco-friendly Kenaf Fiber Imbedded Nonwoven for Automotive Pillar Trim[END_REF]. As a matter of fact, nonwoven products are especially engineered to create structures that present high specific mechanical properties. Indeed, several studies have shown that nonwoven composites exhibit good mechanical properties that depend on many parameters such as their different manufacturing preforms as reported by Martin et al. [START_REF] Martin | Evaluation of the potential of three non-woven flax fiber reinforcements: Spunlaced, needlepunched and paper process mats[END_REF]. Mieck et al. [START_REF] Mieck | Needle-punched hybrid nonwovens of flax and PPFibers -Textile semiproducts for manufacturing of fiber composites[END_REF] have studied the effect of fibre content on the tensile characteristics of needle punched flax-PP nonwoven composites and they have highlighted a strong increase in the tensile properties with the fibre content. Roussière et al. [START_REF] Roussière | Compressive and tensile behaviours of PLLA matrix composites reinforced with randomly dispersed flax fibres[END_REF] have been interested in the compressive and tensile behaviour of nonwoven composites constituted of mats of randomly oriented flax fibres that reinforce different types of matrix at a fixed fibre content. The authors have shown that flax-Polylactic acid (PLA) composite presents tensile properties that are equivalent to those of glass-polyester composite. Furthermore, Merotte et al. [START_REF] Merotte | Mechanical and acoustic behaviour of porosity controlled randomly dispersed flax/PP biocomposite[END_REF][START_REF] Merotte | Flax and hemp nonwoven composites: The contribution of interfacial bonding to improving tensile properties[END_REF] have highlighted the interesting acoustical properties of randomly dispersed nonwoven flax-PP composites, that can be obtained by controlling the porosity content within the composite. The best acoustical properties have been obtained for a porosity content of 60%.

The above-cited works on nonwoven natural fibre-reinforced polymer composites have been principally interested in the investigation of their mechanical properties. However, the application of these materials in car interior parts requires better understanding of their damping properties that show their ability to absorb vibrations and dissipate energy. Indeed, the damping phenomena is a major factor that needs to be analysed and improved in order to reduce vibration in structures and avoid fatigue fractures. For this reason, many researchers have already developed several concepts to identify the dynamic properties of synthetic fibrereinforced composite materials [START_REF] Chandra | Damping studies in fiber-reinforced composites -a review[END_REF][START_REF] Sahla | Free vibration analysis of angle-ply laminated composite and soft core sandwich plates[END_REF][START_REF] Draoui | Static and Dynamic Behavior of Nanotubes-Reinforced Sandwich Plates Using (FSDT)[END_REF]. For example, in relation with laminated composites, Sahla et al. [START_REF] Sahla | Free vibration analysis of angle-ply laminated composite and soft core sandwich plates[END_REF] have studied the impact of geometric ratio and fibre angle on the dynamic behaviour of laminated composites using the mathematical model developed by Draiche et al.[27]. This type of composites has also been studied by Abualnour et al. [START_REF] Abualnour | Thermomechanical analysis of antisymmetric laminated reinforced composite plates using a new four variable trigonometric refined plate theory[END_REF] and Belbachir et al. [START_REF] Belbachir | Bending analysis of anti-symmetric cross-ply laminated plates under nonlinear thermal and mechanical loadings[END_REF] in order to investigate its thermomechanical behaviour. Regarding the high interest of using nanoplates and nanotubes as a reinforcement of polymer composites, several research works have recently studied their buckling and vibration behaviours by considering mathematical models [START_REF] Bellal | Buckling behavior of a single-layered graphene sheet resting on viscoelastic medium via nonlocal four-unknown integral model[END_REF][START_REF] Karami | Resonance behavior of functionally graded polymer composite nanoplates reinforced with graphene nanoplatelets[END_REF][START_REF] Semmah | Thermal buckling analysis of SWBNNT on Winkler foundation by non local FSDT[END_REF][START_REF] Bousahla | Buckling and dynamic behavior of the simply supported CNT-RC beams using an integral-first shear deformation theory[END_REF][START_REF] Medani | Static and dynamic behavior of (FG-CNT) reinforced porous sandwich plate using energy principle[END_REF]. For instance, Medani et al. [START_REF] Medani | Static and dynamic behavior of (FG-CNT) reinforced porous sandwich plate using energy principle[END_REF] have investigated the dynamic behaviour of graded carbon nanotube-reinforced porous sandwich plates using a model based on the First Shear Deformation Theory. Among all the tested parameters, the authors have founded that the variation of porosity has the greatest influence on the vibration properties.

For natural fibre-reinforced woven composites, several research works have already highlighted their good damping properties particularly by using the dynamic mechanical analysis (DMA) [START_REF] Duc | Damping of thermoset and thermoplastic flax fibre composites[END_REF][START_REF] Duc | Dynamic mechanical properties of epoxy/flax fibre composites[END_REF][START_REF] Wielage | Processing of natural-fibre reinforced polymers and the resulting dynamic-mechanical properties[END_REF] or free vibration analyses [START_REF] Assarar | Analysis of the Damping of Sandwich Materials and Effect of the Characteristics of the Constituents[END_REF][START_REF] Assarar | Evaluation of the damping of hybrid carbon-flax reinforced composites[END_REF][START_REF] Cheour | Effect of water ageing on the mechanical and damping properties of flax-fibre reinforced composite materials[END_REF]. For example, Duc et al. [START_REF] Duc | Damping of thermoset and thermoplastic flax fibre composites[END_REF][START_REF] Duc | Dynamic mechanical properties of epoxy/flax fibre composites[END_REF] have compared the dynamic properties of unidirectional and twill flax, carbon and glass fibrereinforced composites by using the DMA. Their results have shown that composites based on flax fibres exhibit higher damping properties than glass and carbon composites [START_REF] Duc | Damping of thermoset and thermoplastic flax fibre composites[END_REF]. Duc et al. have attributed this difference to the fibre-matrix interphase and the different friction mechanisms intrinsic to flax fibre yarns such as the intra-cell and inter-cell wall frictions.

Furthermore, these authors have analysed the effect of fibre-matrix adhesion, fibre diameter and the twist angle of yarns in flax fabrics and have shown their important influence on the damping properties of the studied woven composites [START_REF] Duc | Dynamic mechanical properties of epoxy/flax fibre composites[END_REF]. Similar results have been found by Wielage et al. [START_REF] Wielage | Processing of natural-fibre reinforced polymers and the resulting dynamic-mechanical properties[END_REF] who have investigated the dynamic properties of flax, hemp and glass fibre-reinforced polypropylene composites and have proven that the loss factor of composites based on flax and hemp fibres is relatively higher than that of glass composite. In addition, the dynamic behaviour of commingled, sandwich and hybrid composites has been significantly investigated [START_REF] Assarar | Analysis of the Damping of Sandwich Materials and Effect of the Characteristics of the Constituents[END_REF][START_REF] Assarar | Evaluation of the damping of hybrid carbon-flax reinforced composites[END_REF][START_REF] Assarar | Damping analysis of sandwich composite materials[END_REF][START_REF] Monti | Experimental and finite elements analysis of the vibration behaviour of a bio-based composite sandwich beam[END_REF][START_REF] El-Hafidi | Determination of dynamic properties of flax fibres reinforced laminate using vibration measurements[END_REF][START_REF] George | Viscoelastic behaviour of novel commingled biocomposites based on polypropylene/jute yarns[END_REF]. For example, Assarar et al. [START_REF] Assarar | Evaluation of the damping of hybrid carbon-flax reinforced composites[END_REF] analysed the effect of stacking sequence on the damping properties of flax-carbon hybrid composites. They have shown a significant increase in the damping properties of flax-carbon hybrid laminates when the flax layers are placed outside the carbon laminate. These authors have also suggested some flaxcarbon configurations that can lead to bending stiffness comparable to that of carbon laminate with enhanced damping properties.

After a literature review, it appears that only few studies have been interested in the damping properties of nonwoven composites [START_REF] Ni | Synchronous improvement of loss factors and storage modulus of structural damping composite with functionalized polyamide nonwoven fabrics[END_REF][START_REF] Zhang | Effect of natural fibre reinforcement on the sound and vibration damping properties of bio-composites compression moulded by nonwoven mats[END_REF]. The work proposed by Ni et al. [START_REF] Ni | Synchronous improvement of loss factors and storage modulus of structural damping composite with functionalized polyamide nonwoven fabrics[END_REF] has dealt with the damping properties of hybrid composites with polyamide nonwoven fabrics. Ni et al. [START_REF] Ni | Synchronous improvement of loss factors and storage modulus of structural damping composite with functionalized polyamide nonwoven fabrics[END_REF] have shown the loss factor enhancement thanks to the polyamide nonwoven fabrics without reducing the storage modulus. The second work by Zhang et al. [START_REF] Zhang | Effect of natural fibre reinforcement on the sound and vibration damping properties of bio-composites compression moulded by nonwoven mats[END_REF] has highlighted the interesting loss factors of compression moulded nonwoven mats based on bamboo, cotton, flax and PLA fibres. This paper proposes a systematical analysis of the damping properties of nonwoven flax, hemp, kenaf and glass fibre-reinforced polypropylene composites, using free-free flexural vibration tests. The obtained results were analysed referring to the microstructure of the fibres and the matrix. Furthermore, the effect of the porosity content, fibre orientation and fibre/matrix weight ratio on the damping properties of these materials was investigated.

Finally, a prediction of the loss factor in term of the porosity content is proposed.

Materials

The nonwoven composites studied in this work were supplied by Ecotechnilin SAS in France and were elaborated from flax, hemp, kenaf, glass and polypropylene commingled fibres. The flax-PP, hemp-PP, kenaf-PP and glass-PP nonwoven fabrics were manufactured using the carding/cross lapping/needle punching process at a fibre matrix ratio of 50 % wt [START_REF] Russel | Handbook of Nonwovens[END_REF]. They are known under the commercial name "FibriPlast 300" and their areal weight is 273 ± 16 g/m 2 . The plates of nonwoven composites were manufactured by platen press process: the commingled fabrics were cut under shapes of 210×300 mm 2 and placed between two steel trays to be hot pressed at 11 bar and 200°C. The hot nonwoven fabrics were then placed between cooled plates and pressed for 1 minute in order to obtain a final thickness of 1.9 mm. Note that the number of plies of each fabric depends on the desired porosity content of the final composite. Indeed, the thickness of each composite plate was fixed to 1.9 mm and the number of plies stacked into the mould varies between 2 and 8 plies in order to obtain a porosity content between 9 % and 64 %. Finally, the composite samples were cut, using a laser cutting machine, from each composite plate in the Machine Direction (MD) and the Cross Direction (CD) for the different tests. Table 1 summarizes the different characteristics of the studied materials.

The porosity content of each composite was determined according to the ASTM D2734-09 standard using the following expression:

1 1 ( ) f f c m f w w φ ρ ρ ρ - = - + (Eq. 1)
where f w is the fibre weight ratio and c ρ , m ρ , f ρ are the composite, matrix and fibre densities, respectively. Note that c ρ is measured from the weight and the volume of each composite sample.

Experimental procedure

The dynamic properties of the nonwoven composite samples were determined using free flexural vibrations tests with test-specimens of 25 mm wide. Three lengths of these specimens (230, 250 and 270 mm) were also considered to obtain a variation of the peak frequencies of the response signals. Each specimen was suspended vertically by two fine rubber wires to obtain free-free boundary conditions as shown in Figure 1. Next, it was excited manually at different points using an impulse hammer PCB 086C03. The specimen response was then detected by an accelerometer PCB 352C23, which measures the acceleration of the transverse vibrations.

The excitation and the response signals were digitalized by the LMS SCADAS dynamic analyser that allows displaying the deformed shapes using LMS PolyMax (Polyreference Modal Analysis eXtended) [START_REF] Peeters | The PolyMAX frequency domain method: a new standard for modal parameter estimation[END_REF]. Finally, the natural frequencies of each composite sample and their associated loss factors were derived by fitting the experimental Frequency Response Functions (FRF) to the PolyMax FRF [START_REF] Peeters | The PolyMAX frequency domain method: a new standard for modal parameter estimation[END_REF].

Results and discussions

Influence of the reinforcement fibre type

In this section, the damping properties and the bending moduli of glass-PP, kenaf-PP, hemp-PP and flax-PP nonwoven composites are compared for a fixed porosity content of ~20% and 50% weight of fibre. Figure 2 shows the evolution of their loss factors with the frequency in the machine and the cross directions. The obtained results firstly show that the loss factor of the studied nonwoven composites varies slightly with the frequency. A similar evolution of the loss factor has been already found in the case of unidirectional and twill flax-epoxy composites [START_REF] Assarar | Evaluation of the damping of hybrid carbon-flax reinforced composites[END_REF][START_REF] Cheour | Effect of water ageing on the mechanical and damping properties of flax-fibre reinforced composite materials[END_REF][START_REF] Assarar | Improving the damping properties of carbon fibre reinforced composites by interleaving flax and viscoelastic layers[END_REF]. Moreover, it is worthy to note the high damping properties of nonwoven composites based on natural fibres when compared with those of the glass-PP composite. Indeed, the loss factor of hemp-PP and flax-PP composites reaches ~5% while it does not exceed ~2% for the glass-PP composite. To better illustrate the difference between the dissipative properties of the tested nonwoven composites, Figure 3 shows a comparison between their loss factors at a fixed frequency of 500 Hz. We remark that those of flax, hemp and kenaf nonwoven composites are 2 to 2.50 times higher than that of the glass-PP composite. These relatively high damping properties reflect the capacity of these materials to absorb vibrations and justify their use in car interior parts instead of nonwoven glass reinforced composites.

The relatively good dissipative properties of flax-PP, hemp-PP and kenaf-PP composites shown in Figures 2 and3 can be essentially explained by the interesting damping properties of natural fibres as reported in several literature results [START_REF] Duc | Damping of thermoset and thermoplastic flax fibre composites[END_REF][START_REF] Duc | Dynamic mechanical properties of epoxy/flax fibre composites[END_REF][START_REF] Assarar | Evaluation of the damping of hybrid carbon-flax reinforced composites[END_REF][START_REF] Assarar | Improving the damping properties of carbon fibre reinforced composites by interleaving flax and viscoelastic layers[END_REF]. In fact, natural fibres have a form of bundle of unit fibres, which are not perfectly separated and gathered in groups. This grouping of unit fibres induces friction mechanisms between them, which lead to an energy dissipation within the fibre creating more damping capacity. This could be supported by the Scanning Electron Microscopy (SEM) micrographs of glass-PP and hemp-PP composites presented in Figure 4. These observations highlight the difference of fibre structure between synthetic and natural fibres. In fact, the presence of groups of elementary fibres in the hemp fibre architecture induces a high internal friction leading to more dissipation of energy by the composite. Moreover, the morphology of natural fibres generates a supplementary source of energy dissipation caused by the friction between the primary and the secondary walls of each elementary fibre, and between the cellulose microfibrils, the hemicellulose and the lignin of each wall [START_REF] Bourmaud | Relationships between micro-fibrillar angle, mechanical properties and biochemical composition of flax fibers[END_REF].

In order to select the nonwoven composite that presents the best compromise between bending stiffness and damping, Figure 5 shows a comparison between five properties of the four tested nonwoven composites in the machine direction: bending modulus, fibre volume fraction, composite density, loss factor and porosity content. The axes are represented with the most beneficial values towards the outside of the diagram, which means that, from the five features, the larger the area built is, the better the composite materials are considered. Note that the bending moduli of the nonwoven composites were determined based on the natural frequencies. They were determined by the following expression in the case of free-free configuration [52]:

3 2 2 12 f i i s E h w L λ ρ = , ( 2 1)
.( / 2) 1,.., 7

i i i λ π = + = (Eq. 2)
where f E is the bending modulus, L the length, h the thickness and s ρ the surface density of the nonwoven composite beam. i λ is a coefficient for the free-free configuration [START_REF] Assarar | Analysis of the Damping of Sandwich Materials and Effect of the Characteristics of the Constituents[END_REF] and i is the flexural mode number.

The fibre volume fractions of the nonwoven composite samples were determined by the following expression:

(%)

c f f f v w ρ ρ = × (Eq. 3)
where f w is the fibre weight ratio and c ρ and f ρ are the composite and the fibres densities, respectively.

The radar chart of Figure 5 shows that the change of the fibre type directly affects the selected features. In fact, at the same fibre weight ratio for all the nonwoven composites, the fibre volume fraction of glass-PP is clearly lower than those of flax-PP, kenaf-PP and hemp-PP composites which is principally due to the high density of synthetic fibres compared with natural ones. Moreover, the use of glass fibres enhances the bending modulus of the composite regarding to the relatively high stiffness of the glass fibre compared with flax, hemp and kenaf fibres. However, this decreases the glass-PP loss factor because of the lack of energy dissipation within the synthetic fibre microstructure. Indeed, the loss factors of natural fibre reinforced nonwovens are significantly higher than that of glass-PP. For the kenaf-PP composite, its area in the radar chart increases compared with the glass-PP. In addition, the use of kenaf fibres as reinforcement clearly decreases the loss factor and doesn't lead to a significant improvement of the bending modulus compared with hemp or flax reinforced nonwoven composites. The hemp-PP and flax-PP composites have areas that increase more significantly than the kenaf-PP and shifts to the downer part of the diagram. This means that these composites ensure the best damping properties with a low density. Their bending moduli remain lower than those of glass-PP composite but they can be comparable if we consider the difference of density between glass and flax or hemp fibres.

Therefore, for applications necessitating high absorption of vibrations and stiffness properties combined with a low weight, hemp-PP and flax-PP nonwoven composites can be highly recommended.

Regarding the relatively high use of flax fibres among plant fibres as reinforcement in natural fibre-reinforced composites [START_REF] Khalfallah | Innovative flax tapes reinforced Acrodur biocomposites: A new alternative for automotive applications[END_REF][START_REF] Poilâne | Polymer reinforced by flax fibres as a viscoelastoplastic material[END_REF], as well as the interesting damping and stiffness properties of the flax-PP nonwoven composite, the following studies are only conducted on this material.

Influence of fibre orientation

The results presented in the latter section show that the loss factor in the machine direction seems to be slightly higher than that in the cross direction. Consequently, free flexural vibration tests were conducted on flax-PP nonwoven samples in several directions (0, 30, 45, 60 and 90°) in order to quantify the influence of fabrics orientation on their dynamic properties. Figure 6 depicts the evolution of the loss factor and the natural frequency of flax-PP with respect to fabrics orientation, for the third and the fifth flexural bending modes. This figure shows that the flax-PP loss factor and flexural frequency vary very slightly from the machine (0°) to the cross direction (90°). This slight variation can be explained by the apparition of a preferred orientation of the nonwoven fabrics during the carding/overlapping/needle punching process [START_REF] Russel | Handbook of Nonwovens[END_REF].

Influence of the fibre/matrix weight ratio

In this section, the influence of fibre content on the loss factors and the flexural frequencies of the flax-PP nonwoven composite is analysed. To this end, three flax fibre/PP matrix weight ratios are considered: 30/70, 50/50 and 70/30. This study is conducted at a fixed porosity content of about 20% as summarized in Table 1. The evolution of the first five natural frequencies and their associated loss factors with the fibre weight ratio is depicted in Figures 7 and8, respectively. These results show that the first five flexural frequencies slightly increase with the flax fibre weight ratio. The slight increase of the 70/30 wt% flax-PP composite frequency can be related to the higher stiffness and density of flax fibres compared with the flax-PP composite with 30% of fibre weight ratio. The results of Figure 8 clearly show that the damping of flax-PP decreases with the flax fibre weight content. For example, this decrease is about 17.9% to 24.28% when increasing the flax weight ratio from 30 to 70% in the machine and the cross directions, respectively. In fact, the damping properties of the PP matrix are higher than those of the flax fibre [START_REF] Duc | Damping of thermoset and thermoplastic flax fibre composites[END_REF][START_REF] Cheour | Effect of water ageing on the mechanical and damping properties of flax-fibre reinforced composite materials[END_REF] which allows further dissipation of energy and absorption of vibrations in particular for the flax-PP composite with 30% of fibre weight ratio. However, the use of flax fibres with high weight ratio (70%) results in a significant decrease of the loss factor. This could be explained by the decrease of the matrix contribution in the energy dissipation process of the flax-PP composite. Accordingly, the decrease in the loss factor when increasing the flax fibre weight ratio firstly indicates that the damping properties of the matrix are superior to those of the flax fibre. Secondly, it shows that the damping phenomena induced by the polypropylene matrix is predominant compared to other damping mechanisms such as those related to the friction between flax fibres, the fibre/matrix interaction and the architecture of flax fibres as discussed in section 4.1.

Influence of the porosity content

In view of the high porosity content present in nonwoven composites intended for car interior parts, it is crucial to analyse its contribution in the damping performance of these composites.

To this end, flax-PP composites with five porosity contents (9, 22, 37, 50 and 64%) and fixed fibre weight ratio of 50% were tested in the machine and the cross directions and the obtained results are depicted in Figure 9. These results indicate that the loss factor of flax-PP significantly increases with the porosity content as it reaches approximately 8% for a porosity content of 64%. In fact, an increase of 611% of the porosity content (from 9 to 64%) enhances the loss factor by 108.7%.

These interesting damping properties of the flax-PP nonwoven composite are essentially related to the high damping properties of the nonwoven flax fibres and the polypropylene matrix, as discussed in sections 4.1 and 4.3, in addition to the morphology of this porous material. In fact, SEM micrographs of the flax-PP composite cross section at ~7, 32 and 48% of porosity content, depicted in Figure 10, confirm the presence of voids that are connected to each other and located at the fibre/matrix interface. These voids increase with the porosity content and become more and more connected, which explain the relatively high damping properties obtained for the flax-PP nonwoven composite with a very high porosity content.

Indeed, for ~7% of porosity content (Figure 10.a), the pores are very small and not connected to each other which contribute to a good fibre/matrix adhesion. At ~32% of porosity content, the pores are bigger and start to connect to each other leading to a decrease of the quality of the fibre/matrix adhesion (Figure 10.b). At a higher porosity content of ~48% (Figure 10.c), the voids are found to be more connected to each other which causes a poor impregnation of some fibres with the matrix [START_REF] Merotte | Mechanical and acoustic behaviour of porosity controlled randomly dispersed flax/PP biocomposite[END_REF]. This important discontinuity of the fibre/matrix interface induces poor adhesion between the reinforcement and the matrix leading to more energy dissipation within the nonwoven composites with high porosity content.

The obtained loss factors for the five porosity contents in the machine and the cross directions are shown in Figure 11 at a frequency of 500Hz. These curves can be fitted with the following second order polynomial equations:

In the machine direction: In the cross direction: This could help to predict the flax-PP loss factor at a fixed porosity content.

Conclusion

Damping properties of four nonwoven composites (flax-PP, hemp-PP, kenaf-PP and glass-PP)

were investigated in this study using free-free flexural vibration tests. The obtained results

showed that nonwoven composites based on hemp, kenaf and flax fibres present more interesting damping properties than the glass-PP composite. Besides, some material parameters like the fibre/matrix weight ratio and the porosity content were found to have a direct impact on the capacity of the flax-PP nonwoven composite to absorb vibrations. In fact, an increasing of the polypropylene weight ratio within the composite enhances its dissipation of energy and increases its damping properties. Moreover, an increasing of the porosity content clearly enhances the flax-PP damping properties. In addition to that, a prediction of the flax-PP loss factor in term of the porosity content was proposed based on the experimental results. This could be useful to choose the adequate parameters for the flax-PP nonwoven composite regarding the requested damping performance of a specific automotive interior part.

Figure captions:

Figure 1 .

 1 Figure 1. Experimental equipment.

Figure 2 .

 2 Figure 2. Evolution of the loss factor with the frequency for a fixed porosity content of ~20%: (a) the machine direction and (b) the cross direction.

Figure 3 .

 3 Figure 3. Loss factors of the studied nonwoven materials at a fixed frequency of 500 Hz in (a) the machine direction and (b) the cross direction.

Figure 4 .

 4 Figure 4.SEM micrographs of (a) glass-PP and (b) hemp-PP nonwoven composites.

Figure 5 .

 5 Figure 5. Radar chart according to five selected features of the studied nonwoven composites in the machine direction.

Figure 6 .

 6 Figure 6. Evolution of the flax-PP loss factor with the nonwoven fabrics orientation for (a) the third and (b) the fifth flexural modes.

Figure 7 .

 7 Figure 7. Evolution of the flax-PP first five flexural frequencies for three fibre/matrix weight ratios: (a) the machine direction and (b) the cross direction.

Figure 8 .

 8 Figure 8. Evolution of the flax-PP loss factor for three fibre/matrix weight ratios: (a) the machine direction and (b) the cross direction.

Figure 9 .

 9 Figure 9. Evolution of the flax-PP loss factor with the porosity content in (a) the machine direction and (b) the cross direction.

Figure 10 .

 10 Figure 10. SEM micrographs of flax-PP composite cross section at (a) ~7%, (b) ~32% and (c) ~48% of porosity content ((1) disconnected voids and (2) connected voids).

Figure 11 .

 11 Figure 11. Evolution of the flax-PP loss factor with the porosity content at a fixed frequency of 500 Hz in the machine and the cross directions (MD and CD).

Figure 1 .

 1 Figure 1.

Figure 2 .

 2 Figure 2.

Figure 6 .

 6 Figure 6.

Table caption :Table 1 .

 caption1 Characteristics of the studied nonwoven composites.

	Tables :
	Table1
	Composite	Fibre orientation	Fibre/matrix wt (%)	Porosity (%)
	Glass-PP	MD, CD	50/50	23.00±2.30
	Kenaf-PP	MD, CD	50/50	22.36±2.40
	Hemp-PP	MD, CD	50/50	19.91±1.69
	Flax-PP	MD, 30°, 45°, 60°, CD	50/50	22.31±2.01
	Flax-PP	MD, CD	30/70 70/30	22.42±1.29 23.49±2.23
				08.82±1.22
				22.31±2.01
	Flax-PP	MD, CD	50/50	36.53±2.95
				50.27±1.81
				63.53±1.21
			1

Acknowledgements

The authors would like to gratefully acknowledge the LASMIS research team (Institut Charles Delaunay, University of Technology of Troyes, France) for using its Optical Microscope. The authors would also like to thank EcoTechnilin SAS for supplying the nonwoven materials.


MD François Chaumier

MD Thomas Flament

MD, PhD Thierry Lecomte

MD Hélène Vegas

MD Marion Stacoffe

MD Eric Pichon

MD Bérangère Narciso

MD Morgane Caulet

MD Catherine Barbe

MD Anaïs Jaillais

MD Delphine Carmier

MD Marie-Agnès By

PhD Marianne Bourdon

PhD Jean-Benoît Hardouin

Cross-Cultural Adaptation and Psychometric Validation of the French Version of the FAMCARE-Patient (FFP-16) Questionnaire for Outpatients With Advanced-Stage Cancer

Keywords: Satisfaction, questionnaire, cancer, cross-cultural, validation, psychometric

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

BACKGROUND

The quality of care indicates the adequacy of caregivers' responses in satisfying the needs and expectations of patients [START_REF] Coulter | Measuring and improving patients' experiences: How can we make health care systems work for patients? In: Measuring up: improving health system performance in OECD countries[END_REF]. Using a sample of 2249 American patients, Jenkinson identified three areas of patient care that influence satisfaction: (i) physical comfort and symptom management, (ii) emotional support and caregivers' availability, and (iii) respecting the patient's wishes and his/her place in decision-making [START_REF] Jenkinson | Patients' experiences and satisfaction with health care: results of a questionnaire study of specific aspects of care[END_REF]. In advanced stages of a serious illness, satisfaction level is known to be correlated to the quality of life [START_REF] Lynn | Measuring quality of care at the end of life: a statement of principles[END_REF] and "quality of dying"(4), which includes accessibility, symptom management, emotional support, coordination and personalization of care, communication and education, and finally active participation in decision-making [START_REF] Kaasa | Quality of life in palliative care: principles and practice[END_REF][START_REF] Hales | The quality of dying and death[END_REF].

The FAMCARE-Patient scale or FAMCARE-P16 questionnaire [START_REF] Lo | Measuring patient satisfaction in oncology palliative care: psychometric properties of the FAMCARE-patient scale[END_REF][START_REF] Lo | The FAMCARE-Patient scale: measuring satisfaction with care of outpatients with advanced cancer[END_REF] is the only satisfaction assessment tool specifically designed for outpatients with advanced-stage cancers. It is a selfadministrated survey that was constructed on the basis of the 20-item FAMCARE measure for family satisfaction with care [START_REF] Kristjanson | Validity and reliability testing of the FAMCARE Scale: measuring family satisfaction with advanced cancer care[END_REF]. It is structurally composed of 16 items, cohered into a single patient satisfaction factor. Each item is evaluated using a 5-point Likert scale (1-5; 1, very dissatisfied; 5, very satisfied), with a total score ranging from 16 to 80. Patients with an individual score of ≥64 are considered to be generally satisfied because this cut-off value is associated with a rating of 4 (satisfied) on all 16 items. This tool demonstrated high internal reliability, and patient satisfaction can be modified accordingly by a palliative care intervention [START_REF] Follwell | Phase II study of an outpatient palliative care intervention in patients with metastatic cancer[END_REF][START_REF] Zimmermann | Early palliative care for patients with advanced cancer: a cluster-randomised controlled trial[END_REF][START_REF] Groenvold | Randomised clinical trial of early specialist palliative care plus standard care versus standard care alone in patients with advanced cancer: the Danish Palliative Care Trial[END_REF].

In French, there is currently no tool dedicated to the assessment of satisfaction in outpatients with advanced-stage cancers. This entails the use of non-validated and heterogeneous measurement tools in this population. The aim of our study was to cross-culturally adapt the FAMCARE-Patient questionnaire for the French population and to subsequently perform a psychometric validation of this French version.

METHODS

Cross-cultural adaptation process

The FAMCARE-P16 questionnaire was translated into French following standard recommendations [START_REF] Beaton | Guidelines for the process of cross-cultural adaptation of self-report measures[END_REF]. Forward-backward translations were performed by four people-two native English speakers and two native French speakers-fluent in French and English. The backward translation was compared to the original version by the author herself. The forward semantic translated version was adapted to French cultural context and lifestyle by an expert committee with oncology and palliative care physicians and nurses, psychologists, anthropologist, and linguistic researchers and methodologists as members. A pre-final version was pilot tested using cognitive debriefing interviews to evaluate the acceptability and comprehension of each item. Modifications were made according to patients' comments, and the final version of the French FAMCARE-P16 (FFP-16) questionnaire was validated by the expert committee.

Psychometric validation process and analyses

Design

This was a single-centre, cross-sectional, and observational study specifically designed to validate the FFP-16 questionnaire. All procedures performed in the study were in accordance with the ethical standards of the institutional research committee (Committee for the Protection of Persons consenting to biomedical research, n°2015-S15). This study was registered in the European trial register (EudraCT n°2015-A01707-42).

Patients

Informed consent was obtained individually from all participants included in the study. The inclusion criteria were the same as those for the validation of the original English version: diagnosis of an advanced-stage cancer, i.e. metastatic gastrointestinal, genitourinary, breast, lung, or gynaecological cancer (for lung cancer, stages IIIA and B were included; patients with metastatic breast or prostate cancer who were refractory to hormonal therapy and those with locally advanced pancreatic cancer were included); >18 years of age; native French-speakers; and ambulatory patients with an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2. ECOG score is provided on a 6-point scale (0-5; 0, fully active; 5, dead) that assesses the patient's ability for selfcare and ambulation.

Patients were all recruited from the outpatient clinic or chemotherapy day hospital of the University Hospital of Tours (France).

Questionnaires and Data Collection

During the psychometric validation process, two other questionnaires were selected in addition to the FFP-16 questionnaire. Patients completed all questionnaires, i.e., self-administrated FFP-16 questionnaire, the French versions of the QLQ-C15-PAL questionnaire from the European Organization for Research and Treatment of Cancer (EORTC), and the Edmonton Symptom Assessment Scale (ESAS), in the hospital on day-1.

EORTC-QLQ-C15-PAL is a 15-item quality-of-life questionnaire validated in advanced stages of cancer. Fourteen items, which are related to nine functional and symptom scales, were evaluated using a 4-category Likert scale. The last item is a 7-point global quality-of-life scale with a score ranging from 1 (very poor) to 7 (excellent) [START_REF] Groenvold | The development of the EORTC QLQ-C15-PAL: a shortened questionnaire for cancer patients in palliative care[END_REF].

ESAS was designed to assess nine symptoms that commonly occur in patients with cancer.

Severity of each symptom is rated from 0 to 10 on a numerical scale [START_REF] Bruera | The Edmonton Symptom Assessment System (ESAS): a simple method for the assessment of palliative care patients[END_REF].

Questionnaires were collected by a protocol researcher. Some of the patients were asked to complete the FFP-16 questionnaire at home on day-3 to provide data for the assessment of testretest reliability. This interval was chosen to be long enough so that the patients forgot their previous answers and close enough so that their clinical condition has not changed. Completed questionnaires were mailed back to the coordinator of the participating centre with a pre-stamped envelope.

Data on patients' clinical and demographic characteristics were also collected at inclusion.

Sample Size

A sample size of more than 100 patients is considered as a "very good" indicator of the quality of a patient-reported outcome measurement, according to the COSMIN recommendations [START_REF] Terwee | COSMIN methodology for evaluating the content validity of patient-reported outcome measures: a Delphi study[END_REF]. Our sample size determination was defined a priori with a subject to item ratio of 10 and was set to a minimum of 160 patients.

Analyses

Analyses were conducted using Stata 15.1 (StataCorp LLC, College station, TX, USA). Missing data were handled by Personnal Mean Score (PMS) imputation [START_REF] Huisman | Imputation of missing item responses: some simple techniques[END_REF]. Validity of the questionnaire was appreciated using several indices [START_REF] Vet Hcw De | Measurement in medicine: a practical guide[END_REF].

-Content validity was determined on the basis of qualitative evaluation, which involves the judgement of coherence between the original and translated items and their relevance, by experts.

-Face validity was defined on the basis of interviews with the patients included in the cross-cultural adaptation process and by a quantitative analysis of the validation sample (rate of missing data and time to complete the questionnaire).

-Structural validity was evaluated by a confirmatory factor analysis (CFA) of patients' responses during the validation process, to confirm the one factor structure of the original English tool. A good fit is indicated by a comparative fit index (CFI) of >0.95 and a root mean square error of approximation (RMSEA) of <0.05. An acceptable fit is indicated by a CFI of 0.90-0.95 and a RMSEA of 0.05-0.08 [START_REF] Gadelrab | Evaluating the fit of structural equation models: sensitivity to specification error and descriptive goodness-of-fit Indices[END_REF]. A factor loading of >0.5 was expected for each item.

-Reliability of the FFP-16 score was computed using the Cronbach's alpha coefficient (α > 0.7 was expected) [START_REF] Vet Hcw De | Measurement in medicine: a practical guide[END_REF].

-Coherence of the FFP-16 responses was evaluated using the Mokken's model (a correct fit is indicated by Loevinger's coefficient of scalability (H) > 0.3, a good fit by H > 0.5) [START_REF] Sijtsma | Introduction to nonparametric item response theory[END_REF].

-Reproducibility of the FFP-16 score was computed using intraclass correlation coefficient (ICC; >0.6 was expected) [START_REF] Shrout | Intraclass correlations: uses in assessing rater reliability[END_REF].

-Criterion validity was determined by analysing non-trivial Spearman's correlation of the FFP-16 score with scores obtained from the EORTC-QLQ-C15-PAL and ESAS questionnaires [START_REF] Vet Hcw De | Measurement in medicine: a practical guide[END_REF]. Our a priori hypothesis was an independence between the concept of satisfaction, performance status, symptoms, and quality-of-life.

RESULTS:

Cross-cultural adaptation and face validity

According to the original author of the FAMCARE-Patient questionnaire, there is no difference in meaning between the original version and the backward translated version. Content validity of the French version was assessed by the expert committee, and some items were reformulated to facilitate adaptation to French language and cultural context (Supplemental Data). A pilot version was tested by conducting interviews with 29 eligible patients. Most of the items were found to be clear and easy to understand; however, changes in format were needed with regard to three items (questions about prognosis and family) to limit misunderstanding and missing data.

These successive modifications were tested with 12 then 10 additional patients, ie 51 patients in the cross-cultural adaptation process (Figure 1).

With regard to acceptability, the translated questionnaire was considered to be good or very good by all patients. The completion mean time was 5.1 min (standard deviation 1.4 min).

Psychometric validation process

Patients

One hundred and seventy-six adults participated in the validation study. Their sociodemographic and clinical characteristics are presented in Table 1. The overall educational level was low. Time since diagnosis was <2 years in 95 patients (54%). Most patients received chemotherapy or hormonotherapy (97%) and were recruited from the chemotherapy day hospital (91%).

Acceptability and item-descriptive statistics

Item acceptability was considered to be good, except for three items with >10% missing data.

Table 2 presents standardised factor loading for each item, all of which are >0.6 -better than the expected value. There was no floor or ceiling effects for all the items.

Statistical analyses

CFA indicated that a one-factor structure had an acceptable fit to the FFP-16 questionnaire, with CFI = 0.93 and RMSEA = 0.07. Internal reliability was high as shown by Cronbach's alpha (α = 0.95) and coherence of the responses to the questionnaire was strong as shown by H values (significantly positive and >0.5) (Table 2). Furthermore, reproducibility of the FFP-16 score in 43 patients was very good (ICC = 0.91).

We correlated the summed score of the FFP-16 questionnaire with that of the ECOG, EDS, individual ESAS items, and individual QLQ-C15-PAL subscales. The FFP-16 score did not significantly correlate with the scores of these scales, with the exception of the anxiety-and well-being-related scores of ESAS (Spearman's correlation coefficient = -0.18 and -0.20 respectively, p < 0.05) and the overall quality-of-life score of QLQ-C15-PAL (Spearman's correlation coefficient = 0.30, p < 0.05).

DISCUSSION:

The cross-cultural adaptation of the FAMCARE-P questionnaire for the French population was achieved with satisfaction, and this version showed satisfactory psychometric properties in terms of structure, reliability, coherence, and reproducibility. CFA confirmed the validity of original one-factor model of the FFP-16 questionnaire. Regarding the reliability of the FFP-16 questionnaire, statistical analysis demonstrated an adequate internal consistency. This questionnaire was confirmed to be acceptable to patients. However, there was a significant quantity of missing data with regard to two items about loved ones (items 15 and 16). Most of the patients who did not answer these items did not identify relatives (family or friends) for the dedicated previous question. They may not have been concerned but they had no possibility of a "not applicable" response.

Compared to the original English version, the FFP-16 questionnaire showed an acceptable fit of a single-factor structure, with higher Cronbach's alpha (0.95 vs. 0.94), higher CFI (0.93 vs. 0.88) and lower RMSEA (0.07 vs. 0.11) [START_REF] Lo | The FAMCARE-Patient scale: measuring satisfaction with care of outpatients with advanced cancer[END_REF]. Factor loadings of the French version were approximately same as those of the original version [START_REF] Lo | Measuring patient satisfaction in oncology palliative care: psychometric properties of the FAMCARE-patient scale[END_REF][START_REF] Lo | The FAMCARE-Patient scale: measuring satisfaction with care of outpatients with advanced cancer[END_REF]. An English shorter 13-item version (FAMCARE-P13) showed an acceptable fit compared to the poor one of the original 16-item version, but with a lower internal reliability [START_REF] Lo | The FAMCARE-Patient scale: measuring satisfaction with care of outpatients with advanced cancer[END_REF]. The FAMCARE-P13 was also translated from English to Greek [START_REF] Parpa | Psychometric properties of the patients' satisfaction instrument FAMCARE-P13 in a palliative care unit[END_REF]. In this study, the CFA showed a very poor CFI with a one-factor structure (0.59). It could be explained by translation errors or by Greek cultural specificities. Moreover, the Greek study used the FAMCARE-P13 in patients hospitalized in palliative care units, contrary to the original tool in ambulatory patients. In this work, the secondary exploratory factor analyses identified a two-factor structure with an acceptable fit. In our study, CFA confirmed a one-factor model with an acceptable fit and we found a good reliability of the 16-item version, better than the 13-item version (Cronbach's alpha 0.95 vs 0.94).

In our work, the satisfaction score was not correlated with the patient's overall condition.

Indeed, the ECOG score assesses the patient's ability to take care of himself and to move around. In advanced stages of cancer, this autonomy is often limited and decreased by fatigue. The absence of correlation between the FFP-16 score and ECOG status demonstrates that satisfaction is a distinct concept, independent of the patient's physical performance. We also found that satisfaction was not correlated with the overall ESAS distress score as well as individual ESAS physical symptom score.

These results further show that the concept of satisfaction is independent of the patient's general and physical condition. FFP-16 score was significantly correlated with the well-being and anxiety scores of ESAS as well as the overall QLQ-C15-PAL quality-of-life score. This could be explained by the subjective dimension of the concept of satisfaction, which can be influenced by uneasiness, anxiety, or a feeling of poor quality-of-life. It was similar for the original English FAMCARE-Patient questionnaire validation [START_REF] Lo | The FAMCARE-Patient scale: measuring satisfaction with care of outpatients with advanced cancer[END_REF]. However, these correlations are weak and close to independence. Moreover, we did not find correlation between FFP-16 score and the emotional functioning dimension scale of QLQ-C15-PAL questionnaire, which does not allow us to conclude that there is a clear correlation between these concepts. A French questionnaire assessing outpatient satisfaction with care in ambulatory chemotherapy or radiotherapy treatment was adapted from the In-Patsat32 questionnaire from the EORTC [START_REF] Can | A psychometric validation study of the Quality of Life and FAMCARE scales in Turkish cancer family caregivers[END_REF]. It was not dedicated to patients with advanced-stage cancer but exclusively to patients undergoing cancer treatment. CFA revealed good convergent validity and excellent internal consistency. Items and subscales of this questionnaire were not significantly correlated to the quality of life, emphasising that satisfaction and quality of life are distinct concepts.

Our study could be criticized for choosing a questionnaire that is based on the data initially collected from American or Canadian patients. Indeed, it has not been demonstrated that French patients with advanced stages of cancer do have the same areas of satisfaction with care as North American patients. However, during the individual interviews for the cross-cultural adaptation process, most patients felt that the tool was suitable for assessing their satisfaction-with no missing areas identified. Furthermore, using the same questionnaire that is validated in several languages, improves the possibility of promoting international research. Secondarily, our work could also be criticized for changing the form of the questionnaire, particularly with regard to family-related items.

This was necessary to limit missing data for these items. During the individual interviews, questions about family and its place in medical decisions were misinterpreted because patients were committed to medical confidentiality and self-decision. This could be explained by a French cultural specificity. That is why this change in form can be justified by a rigorous transcultural adaptation according to the French cultural context. Finally, we regret the absence of items related to the emotional, social and spiritual dimensions, especially in a questionnaire dedicated to patients with advanced stages of cancer. However, we have chosen to focus on the existing questionnaire without creating a new one. Despite these potential shortcomings, we obtained a version of the FAMCARE-P questionnaire adapted to the French cultural context, with good psychometric properties and according to a rigorous methodology.

CONCLUSION:

The present study will allow the use of a validated French scale to evaluate the satisfaction of outpatients with advanced stages of cancer. This will facilitate the improvement of the quality of patient care by caregivers and physicians. This will also allow the use of a validated tool in clinical research for international multicenter studies. This study will be continued with the development of a new clinical tool to assess patients' issues and supportive care needs, in order to improve their satisfaction of care.

Figure

  Figure 1. French version of the FAMCARE-Patient questionnaire (FFP-16) Legend: 1 (very dissatisfied), 2 (dissatisfied), 3 (undecided), 4 (satisfied), 5 (very satisfied)

1 .

 1 French version of the FAMCARE-Patient questionnaire (FFP-16)

	Legend: 1 (very dissatisfied), 2 (dissatisfied), 3 (undecided), 4 (satisfied), 5 (very
	satisfied)
	How satisfied are you with:
	1. Doctor's attention to your description of symptoms
	2. the accuracy with which doctors assess your symptoms
	3. Information given about how to manage pain
	4. Information given about side effects
	5. Speed with which symptoms are treated
	6. Information given about your tests
	7. The way tests and treatments are performed
	8. The way tests and treatments are followed up by the doctor
	9. How you are informed about your illness' progress
	10. Answers from health professionals
	11. Referrals to specialists, if necessary
	12. The availability of doctors to answer your questions
	13. The availability of nurses to answer your questions
	14. Coordination of care

About your close surroundings: Who are your loved ones: family, friends, other ? How satisfied are you with: 15. The availability of doctors to your loved ones Would you involve them in the medical decisions that concern you: yes/no How satisfied are you with: 16. The way doctors respect this choice

Table 1 .

 1 Characteristics of the participants involved in the validation process (N = 176)

	Characteristic	N (%) or	Min-Max	α
		Mean (SD)
	Sex
	Female	96 (55 %)
	Male	81 (45 %)
	Age (years)	64 (11)	23-89
	Married/common-law	117 (70 %)
	Bachelor's degree or higher	55 (31 %)
	Disease site
	Gastrointestinal organs	52 (30 %)
	Breast	40 (23 %)
	Lung	42 (24 %)
	Female reproductive organs	14 (8 %)
	Genitourinary organs	27 (15 %)
	Other	1 (1 %)
	Performance status (ECOG)	0.86 (0.60)	0-2
	ESAS distress score (EDS)	19 (14)	0-73
	FFP-16 score	68 (23)	28-74	0.95
	α = Cronbach's alpha; maximum possible score for EDS = 90; maximum possible score
	for FFP-16 = 80

Table 2 .

 2 Characteristics of FFP-16 items

	Item	Mean (SD)	Missing date	Floor and	Factor loading Loevinger's
			rate	ceiling effects		coefficient (H)
	1	4.4 (0.6)	1%	1% -49%	0.76	0.64
	2	4.3 (0.7)	1%	1% -42%	0.79	0.63
	3	4.2 (0.7)	4%	1% -36%	0.70	0.55
	4	4.1 (0.8)	1%	1% -31%	0.72	0.59
	5	4.3 (0.8)	1%	1% -41%	0.77	0.61
	6	4.1 (0.8)	1%	2% -34%	0.70	0.58
	7	4.4 (0.7)	1%	1% -52%	0.65	0.54
	8	4.4 (0.7)	2%	1% -53%	0.72	0.60
	9	4.2 (0.7)	2%	2% -37%	0.73	0.58
	10	4.2 (0.6)	4%	1% -33%	0.81	0.66
	11	4.2 (0.7)	12%	2% -37%	0.74	0.58
	12	4.3 (0.7)	1%	2% -42%	0.76	0.60
	13	4.5 (0.7)	2%	1% -54%	0.67	0.56
	14	4.3 (0.7)	1%	1% -46%	0.69	0.55
	15	4.2 (0.7)	15%	1% -31%	0.64	0.52
	16	4.3 (0.6)	19%	2% -40%	0.71	0.55

Acknowledgments: We would like to thank R. Aubry and D. Leboul for their help in designing the study and A. Caille, B. Discepoli, F. Etourneau, and D. Mallet for their expert advice. We are grateful to all the patients who participated in this study and to the clinical and research staff of the Chemotherapy Day Hospitals of Oncology, Pneumology and Gastroenterology Department of the University Hospital of Tours.

Funding sources: This study was supported by grants from Fondation de France, Fonds pour les Soins Palliatifs, Ligue contre le Cancer, Société Française d'Accompagnement et de Soins Palliatifs. They had no involvement in the study design, collection, analysis, and interpretation of data, writing the report, or decision to submit the article for publication.

Competing interests:

The authors have no competing interests to declare.