Laura Av Marlow
email: l.marlow@ucl.ac.uk

Jane Wardle

Alice S Forster

Jo Waller

Ethnic differences in HPV awareness and vaccine acceptability

Keywords: Human papillomavirus, knowledge, acceptability, ethnicity, father Word Count: 3, 079

Background -Studies of HPV awareness and HPV vaccine acceptability have included few nonwhite participants, making it difficult to explore ethnic differences. This study assessed HPV awareness and HPV vaccine acceptability in a sample of women representing the major UK ethnic minority groups.

Methods -A cross-sectional study design was used to assess awareness of HPV and acceptability of HPV vaccination. Participants were recruited using quota sampling to ensure adequate representation of ethnic minority women: Indian, Pakistani, Bangladeshi, Caribbean, African, and Chinese women (n=750). A comparison sample of white British women (n=200) was also recruited.

Results -Awareness of HPV was lower among ethnic minority women than white women (6%-18% vs 39% in white women) and this was not explained by generational status or language spoken at home. In the subsample who were mothers (n=601), ethnicity and religion were strongly associated with acceptability of HPV vaccination. Acceptability was highest among white mothers (63%) and lowest among South Asians (11%-25%). Those from non-Christian religions were also less accepting of the vaccine (17-34%). The two most common barriers to giving HPV vaccination were sex-related concerns and side-effects. South Asian women were the most likely to cite sex-related concerns, they were also least likely to believe the vaccine would offer their daughter protection.

Conclusion -These findings suggest some cultural barriers that could be addressed in tailored information aimed at ethnic minorities. They also highlight the importance of recording ethnicity as part of HPV vaccine uptake data.

Introduction

The introduction of human papillomavirus (HPV) vaccination aims to reduce mortality from cervical cancer. The three-dose vaccine is highly effective, providing protection against HPV types 16 and 18, which are responsible for approximately 70% of cervical cancers. [START_REF] Paavonen | Efficacy of a prophylactic adjuvanted bivalent L1 viruslike-particle vaccine against infection with human papillomavirus types 16 and 18 in young women: an interim analysis of a phase III double-blind, randomised controlled trial[END_REF] The UK programme offers vaccination to girls aged 12-13 years. It is expected to cost up to £100m a year and to maximise its benefits, coverage must be high. [START_REF] Kohli | Estimating the long-term impact of a prophylactic human papillomavirus 16/18 vaccine on the burden of cervical cancer in the UK[END_REF] This depends on the vaccine being acceptable to parents.

In the UK, two large studies have explored attitudes to HPV vaccination. [START_REF] Brabin | Future acceptance of adolescent human papillomavirus vaccination: A survey of parental attitudes[END_REF][START_REF] Marlow | Parental attitudes to pre-pubertal HPV vaccination[END_REF][START_REF] Marlow | Trust and experience as predictors of HPV vaccine acceptance[END_REF] The main barriers have been concerns about vaccine side-effects and the sexually-transmitted nature of HPV infection, which provokes worry that the vaccine will promote sexual activity in adolescents. Similar barriers have been identified around the world. [START_REF] Woodhall | Anticipated acceptance of HPV vaccination at the baseline of implementation: a survey of parental and adolescent knowledge and attitudes in Finland[END_REF][START_REF] Lenselink | Parental acceptance of Human Papillomavirus vaccines[END_REF][START_REF] Brewer | Predictors of HPV vaccine acceptability: A theory-informed, systematic review[END_REF][START_REF] Marshall | A cross-sectional survey to assess community attitudes to introduction of Human papillomavirus vaccine[END_REF][START_REF] Chan | Women's attitudes on human papillomavirus vaccination to their daughters[END_REF][START_REF] Ogilvie | Parental intention to have daughters receive the human papillomavirus vaccine[END_REF] In addition, work has shown very low awareness of HPV as a risk factor for cervical cancer. [12;13] To limit inequalities and support informed choice, it is important to understand levels of HPV awareness and HPV vaccine acceptability across all sectors of the population. UK-based studies have included relatively few non-white participants making it difficult to explore ethnic differences. Some of the studies were designed to be population-representative and so this was expected from the outset. [12;13] It also seems that lower response rates occurred for ethnic minority groups. [3;4] Only one study has assessed vaccine uptake in the UK, and it found lower levels in schools with a higher proportion of pupils from ethnic minority backgrounds. [START_REF] Brabin | Uptake of first two doses of human papillomavirus vaccine by adolescent schoolgirls in Manchester: prospective cohort study[END_REF] It is essential that uptake of the HPV vaccine is equitable or the immunisation programme could widen ethnic disparities in health. A first step is therefore to assess ethnic differences in acceptability of the vaccine, and to try to uncover the reasons for any differences. We therefore carried out a survey recruiting participants from the major ethnic minority groups in the UK, with the aims of considering ethnic differences in awareness of HPV and acceptability of HPV vaccination.

Materials and methods

Participants

Data were collected in two waves of the monthly omnibus survey conducted by Ethnibus™ (July and August 2008). Ethnibus™ (www.ethnicfocus.com) recruits participants from the largest ethnic minority groups in proportion to their representation in the UK population. Within each ethnic group, quota-based age distributions are fulfilled. The present sample had a total of 750 female participants from the ethnic minority groups (Indian, Pakistani, Bangladeshi, Caribbean, African and Chinese), plus n=200 white British women.

Postal areas with high proportions of residents from each ethnic group were randomly selected using 2001 census data for England (mostly in London and the Midlands). Multilingual interviewers visited households in these areas and individuals, selected based on their self-reported ethnicity, were invited to participate. Data were collected during face-to-face interviews and each participant received a £5 incentive. Ethnibus™ reported that approximately 70% of individuals who met the eligibility criteria agreed to be interviewed (based on figures recorded by the interviewers) and this was similar to response rates in other Ethnibus™ surveys. The research was exempt from formal ethics committee approval because it ensured complete anonymity.

Measures

All participants were given HPV information based on the Department of Heath's leaflet designed for girls aged 12-13 years and their mothers. This was translated into the most common languages (Urdu, Bangla, Hindi, and Mandarin) by agency-recruited qualified translators, translating into their first language. For all of the other languages (Punjabi, Gujarati, Somali, Sylethi, Uroba, Lugani, Arabic, French, Portuguese), the information was verbally translated during the interview. Questions were developed from previous research and qualitative interviews with 20 ethnic minority mothers. [START_REF] Marlow | Attitudes to HPV vaccination among ethnic minority mothers in the UK: An exploratory qualitative study[END_REF] They were then piloted with 45 women to ensure clarity.

After hearing the information (see supplementary material), women were read the following: 'If you have a daughter age 12-13 years, please think about her when answering the questions; if you don't have a daughter age 12-13 years, please imagine that you do. Starting in September 2008, girls age 12-13 years (year 8) will be offered the HPV vaccination in school. If your daughter were invited to have the HPV vaccination at school this autumn, would you agree to her having it.' Responses were made on a 5-point scale (definitely not -yes definitely). Women were asked to give a reason for their answer which was recorded verbatim. All participants were asked to indicate the father's role in deciding about HPV vaccination because qualitative work indicated possible ethnic differences in this. [START_REF] Marlow | Attitudes to HPV vaccination among ethnic minority mothers in the UK: An exploratory qualitative study[END_REF] At the end of the interview women were asked: 'Before this interview had you heard of HPV (Human Papillomavirus)', with response options of: yes, no, and don't know. This question was asked at the end of the interview in order to avoid confusion regarding similar terms (e.g. HIV) and to encourage women who had heard of HPV but did not remember the name to say yes. Socio-economic class (SEC) was based on the occupation of the chief earner in the household and was coded: AB managerial/professional; C1 supervisory; C2 skilled manual; D semi-skilled/unskilled manual; E state pensioners or casual/lowest grade workers. These groupings are used in market research. [START_REF]Occupation groups[END_REF] Age group, marital status, religion, and language spoken at home were also assessed.

An additional question asked about generational status, classifying women as '2 nd generation' (UK-born and parents UK-born), '1 st generation' (UK-born but at least one parent non UK-born) or 'immigrant' (non UK-born and parents non UK-born). This question was taken from the Millennium cohort study, a prospective study of children in the UK. [START_REF] Hawkins | Influence of moving to the UK on maternal health behaviours: prospective cohort study[END_REF] Generational status is an indicator of acculturation and is an important issue when studying ethnic minorities in the UK. It has been associated with maternal health behaviors (e.g. breast-feeding) and we expected it to influence acceptability of HPV vaccination. For mothers who are 2 nd generation, both they and their parents were born, brought-up and educated in Britain, and would therefore be expected to have more westernised attitudes. Finally, women indicated whether they had any daughters and what ages they were.

Analysis

Data were analysed using SPSS 15.0. HPV awareness and HPV vaccine acceptability was recoded into binary variables. Women responding to the HPV awareness question were catagorised as 'aware of HPV' (yes) or 'not aware of HPV' (no/don't know). Mothers responding to the HPV vaccine acceptability question were coded as 'acceptors' (yes probably/yes definitely) or 'non-acceptors' (probably not/definitely not/unsure). Initially mothers who were 'unsure' were considered as a separate group, but as they were not distinctly different from those who said probably or definitely not, the two groups were combined. Univariate logistic regression analyses were run to identify predictors of HPV awareness and vaccine acceptability. Significant univariate predictors were entered into a multivariate model.

For the free response data, a coding frame was developed (by LM) and applied (by LM and AF) to the mothers' verbatim reasons for their decision. Inter-rater reliability was 'outstanding' (Kappa =.94).

Chi-square analyses were used to explore reasons for the vaccine decision (cited vs. not cited) and involvement of the father (mother takes lead, father takes lead, decide together). For each analysis different ethnic groups were compared to the white group.

Results

Sample characteristics

The sample included 950 women: white British (n=200), Indian (n=235), Pakistani (n=164), Bangladeshi (n=63), Caribbean (n=130), African (n=107) and Chinese (n=51). Sample characteristics are shown in table 1. Most women were aged 25-34 years (26%) or 35-44 years (28%), were married (66%) and were in socioeconomic classes C or D (supervisory, 24%; or manual workers, 49%). Most women reported some religious affiliation (87%), with the majority being Christian (30%) or Muslim (36%). There were roughly equal proportions of 2 nd generation, 1 st generation and 'immigrants'

among Indian, Caribbean, African and Chinese women. There were fewer 2 nd generation Pakistanis and Bangladeshis (15% and 6% respectively). Most respondents spoke English at home (85%), but this varied by ethnicity and migration.

Awareness of HPV

Overall, 17% of women reported (at the end of the interview) that they had heard of HPV before taking part in the study. Univariate logistic regression explored predictors of HPV awareness, odds ratios (ORs) and confidence intervals (CIs) are shown in table 2. There was no association between SEC and awareness of HPV, but there was a slight difference by age, with higher awareness in women aged 16-24 years than women aged 35-44 years (22% versus 13%). There was also a difference in relation to marital status, with higher awareness in single than married women (21% versus 14%).

There was wide variation across ethnic groups, with 39% of white British women having heard of HPV, but much lower awareness in all ethnic minority groups: Chinese (18%), Caribbean (14%), Pakistani (12%), Indian (9%), African (8%) and Bangladeshi (6%). Religion, migration to the UK and language spoken at home were also predictors of awareness in univariate analyses. Fewer Muslim (10%) and more Christian women (27%) were aware of HPV than women with no religion (18%).

There was greater awareness among '2 nd generation' women (24%) than '1 st generation' (14%) or immigrant women (10%) and women who spoke English at home were more likely to have heard of HPV (19%) than those who spoke another language (11%). In multivariate logistic regression, age, ethnicity and religion remained significant (overall model: χ 2 (18)=123.76, p<.001; Nagelkerke R 2 =.21). Marital status, language and generation were no longer significant.

HPV vaccine acceptability

Just under half of the sample (n=440) had a daughter under 16 years old,and of these 137 had a daughter aged 12-13 years. An additional 17% (n=161) had a daughter aged 16 years or older.

Acceptability did not differ based on the daughter's age, so all women with a daughter, regardless of her age, were included in analysis of acceptability (n=601). Overall, 38% of mothers were 'acceptors' (21% yes definitely; 17% yes probably) and 62% were 'non-acceptors' (18% probably not; 19%

definitely not; 25% 'unsure'). Univariate logistic regression explored predictors of HPV vaccine acceptability (ORs and CIs are shown in table 2). There were no associations between HPV vaccine acceptability and age, marital status or SES. Acceptability varied by ethnic group, being highest in white women (63%) followed by African, Caribbean and Chinese women (51%, 49% and 40%), and much lower levels among Indian, Bangladeshi and Pakistani women (25%, 18% and 11%).

Acceptability also varied on the basis of generational status and whether English was spoken at home.

It was higher in '2 nd generation' (50%) than '1 st generation' migrants (35%) and 'immigrants' (25%), and among mothers who spoke English at home (44%) than those who spoke another language (26%).

Religion was associated with acceptability with fewer 'acceptors' among Hindus (34%) and Muslims (18%) compared to those with no religion (64%). In multivariate analyses, which included SEC, only ethnicity and religion remained significant (overall model: χ 2 (13)=129.14, p<.001; Nagelkerke R 2 =.26).

Reasons for intended vaccine decision

Table 3 shows the reasons that mothers cited for their intended vaccine decision. The most common reasons for giving the vaccine were: the protection it would offer from 'HPV' or 'cervical cancer', health reasons e.g. for their daughter's 'health', 'safety' or 'wellbeing', and because of a general positive response to the vaccine, e.g. 'I feel positive about it'. Other reasons included 'peace of mind', 'because there is a need for it', 'because it will be made freely available' and 'because it is part of a parent's responsibility'.

The most common reasons for declining were: needing more information (either about 'side-effects' or generally), sex-related concerns (e.g. 'it encourages promiscuity' or 'risk of premature sex'), religious/cultural reasons (e.g. 'we're very religious, no sex before marriage') and concerns about safety. Other reasons not to give the vaccination included believing it would be unnecessary or inappropriate, age-related reasons (e.g. 12-13 years is too young), lack of trust in vaccinations, and wanting to discuss the decision with other family members.

We explored whether some ethnic groups were more or less likely to cite specific reasons for their decision. Citing the 'protection' that the vaccine would offer occurred less among Indian (16%), Pakistani (11%), Bangladeshi (13%) and Caribbean mothers (14%) compared with white mothers (29%), but there were no differences between white and African or Chinese mothers. Needing more information was cited more by Bangladeshi mothers than white mothers (44% compared to 16%), but there were no differences between white mothers and mothers from any other backgrounds. We were able to look at differences for Indian and Pakistani mothers in citing sex-related reasons, religious reasons, daughter's health and future benefits. Sex-related reasons were more likely to be cited by both Indian (15%) and Pakistani mothers (20%) than white British mothers (2%). None of the other reasons differed significantly. Limited numbers meant that differences could not be explored for Bangladeshi, Caribbean, African and Chinese women (more than 20% of cells in the χ 2 analyses had an expected count of less than 5). Bold -represents when a 2x2 chi-square was used to analyse the difference in that ethnic group compared to the white British group. When figures are not bolded it was not possible to compute χ 2 results because more than 20% of cells in the analysis had a count of less than 5. * p<.05

The role of fathers in deciding about HPV vaccination

Table 4 shows the mothers' responses to the question about fathers' involvement in the decion to vaccinate against HPV. Overall 41% of mothers said they would take the lead in deciding about HPV vaccination and 52% said they would make a joint decision with the father. Again, this varied by ethnic group, with a shared decision most likely in Indian (61%), Pakistani (57%), Bangladeshi (66%), African (63%) and Caribbean groups (56%) and least likely in Chinese (30%) and white groups (36%). In comparison to white British mothers, all ethnic minorities except the Chinese were more likely to share the decision. A small proportion (7%) said the father would take the lead role in deciding about HPV vaccination and this was slightly more common among Chinese (17%), Bangladeshi (16%), Pakistani (10%) and Indian (9%), followed by African (5%) and Caribbean mothers (3%). None of the white mothers said the father would take the lead role in the decision (χ 2 results are not reported for this finding because more than 20% of cells in the analysis had a count of less than 5).

Discussion

Acceptability of HPV vaccination for a 12-13 year old daughter was much lower in ethnic minority mothers than white mothers, with the lowest levels among mothers from South Asian backgrounds.

This was the case even after controlling for SEC. This suggests that previous research with predominantly white British parents cannot be extrapolated to ethnic minority parents, emphasising the importance of including minority women in future research. If these findings map onto uptake, it may mean that some areas of the UK achieve particularly low uptake. The non-white population accounts for 8% across Britain, but this rises to 30% in some areas (Slough, Leicester, Luton, Birmingham and London), and is even greater in parts of London (e.g. Brent: 71% and Newham: 66%). [START_REF] Dobbs | Focus on: Ethnicity and Religion[END_REF] To date, collection of ethnicity data by the NHS has been limited, but this is expected to improve, [START_REF] Vs | Collection of data on ethnic origin in England[END_REF] and the parental consent form for HPV vaccination in England includes a box to record ethnicity. These findings support the importance of monitoring ethnicity in relation to uptake of the HPV vaccination.

Generation and language spoken at home were not significant predictors of acceptability in multivariate analyses, suggesting that acculturation does not mediate the effect of ethnicity. However, religion remained an important factor and 'religious reasons' were one of the main reasons cited for declining the vaccine. This is consistent with previous work that found parents with 'strong religious or cultural views' were less likely to accept HPV vaccination. [START_REF] Brabin | Future acceptance of adolescent human papillomavirus vaccination: A survey of parental attitudes[END_REF] It is also consistent with attitudes to HPV testing, which some minority women felt reflected "nontraditional cultural or religious practices concerning sex and monogamy".[p. 44,[START_REF] Mccaffery | Attitudes towards HPV testing: a qualitative study of beliefs among Indian, Pakistani, African Caribbean and white British women in the UK[END_REF] The importance of religion appears to come from a strong belief in sexual abstinence until marriage, and this is a barrier that will be a challenge to overcome.

There is evidence that South Asian women have fewer sexual partners than white women; nonetheless, 13-29% report more than one lifetime sexual partner and in South Asian men this is nearly 50%. [START_REF] Fenton | Ethnic variations in sexual behaviour in Great Britain and risk of sexually transmitted infections: a probability survey[END_REF] Liaising with religious groups about the best ways to communicate HPV information may help make HPV vaccination more acceptable.

Across the board, one of the most common barriers to accepting HPV vaccination was concern about side effects. This is consistent with a recent study of HPV vaccine uptake [START_REF] Brabin | Uptake of first two doses of human papillomavirus vaccine by adolescent schoolgirls in Manchester: prospective cohort study[END_REF] and was important to all mothers regardless of ethnicity. An additional reason given 'against' HPV vaccination was the belief that the vaccine would 'lead to early sex' or 'encourage promiscuity,' which again has been suggested as a reason for non-acceptability in numerous other studies. [3;4;6;8;10;11] This concern was cited more by South Asian women.

Ethnicity was also associated with HPV awareness, with much lower levels in all the ethnic minority women, particularly Indian, African and Bangladeshi women (<10%). We decided to ask about awareness of HPV at the end of the interview, so that women knew what HPV was before saying whether they had heard of it. This makes it unlikely that levels of awareness are underestimated in this study and means that the findings may not be comparable to other studies which have assessed it at the beginning of the interview. Interestingly, language spoken at home did not explain this effect, suggesting that it is not purely the result of a language barrier. One alternative explanation could be variation in exposure to publicity about HPV due to lower coverage in culturally-specific media or because sex-related topics are considered 'taboo' and as a consequence are discussed less in some cultures. Given that knowledge of HPV is necessary for informed decision-making about vaccination, tailoring information campaigns and channelling these through media outlets aimed at specific ethnic groups may help to raise awareness.

One additional finding of interest was that ethnic minority mothers were more likely to believe the father would play an important role in the decision to vaccinate against HPV. To date there has been little research into fathers' attitudes in the UK, and the Department of Health leaflet about HPV has been aimed explicitly at girls and their mothers. Future research exploring parental decision-making with regard to HPV vaccination among ethnic minorities should include fathers.

There are several limitations to this study. The sampling method means the findings may not be generalisable to all ethnic minority mothers in the population, although the quota sampling technique allowed us to focus on and compare ethnic minority groups. The response rate of 70% was good; however the figure is based on details recorded by the field-interviewers. As the interviewers sometimes forget to report these response details Ethnibus describe the response rate as approximate rather than exact. The response rate should therefore be interpreted with caution. Another issue is that although all mothers in the acceptability analysis had a daughter, not all daughters were aged 12-13 years, and this meant that some mothers were responding hypothetically. Thirdly, we did not assess actual vaccine uptake and statements about intention can only be indicative of acceptance of HPV vaccination. Expected vaccine acceptance in this sample of white mothers was 63%, which was lower than the 75% and 81% that have been found in other studies. [3;4] However, in previous surveys parents were asked to return a questionnaire about vaccination, and thus these studies tend to get responses only from the most 'motivated' parents, whereas in the present study, the questions formed part of a larger survey on a range of issues, so attitudes to this topic are unlikely to have biased participation.

Over the coming years it will be possible to incorporate behavioural outcomes into work on HPV attitudes, but for now exploring acceptability offers some insight into a decision that is facing parents of adolescent girls right now. It gives a head start in understanding possible inequalities before uptake data from the first cohorts of girls are available. Understanding ethnic differences in acceptability of HPV vaccination will be particularly useful to health promotion specialists working in ethnicallydense areas of the country, helping to limit inequalities and support informed choice by all.

What is already known on this subject

• HPV vaccination is now offered to all girls aged 12-13 years.

• In one study, uptake was lower in schools with a higher proportion of ethnic minority pupils.

• One criticism of the UK-based studies is their limited information on non-white participants.

What does this study add

• Ethnicity and religion are predictors of HPV awareness and acceptability of HPV vaccination.

• Sex-related concerns are more likely to be a barrier among ethnic minority parents.

• The ethnic differences found in this study support the importance of monitoring ethnicity in vaccine uptake data.

Table 1 : Sample Characteristics for women in each ethnic group (column percentages)

 1 represents when a 2x2 chi-square was used to analyse the difference in that ethnic group compared to the white British group. When figures are not bolded it was not possible to compute χ 2 results because more than 20% of cells in the analysis had a count of less than 5. * p<.05

		White	Indian	P'stani	B'deshi	C'bbean	African	Chinese
		(n=200)	(n=235)	(n=164)	(n=63)	(n=130)	(n=107)	(n=51)
	Age
	16-24	10	20*	23*	29*	22*	20*	24*
	25-34	29	29	24	24	24	30	18
	35-44	25	26	34	25	22	35	43*
	45-54	17	12	10	16	15	9	16
	55+	21	15	10*	6*	17	7*	0*
	Marital status
	Married/Cohabitating	73	63*	71	78	52*	62	71
	Single	21	25	25	8*	42*	34*	22
	Divorced/Separated/Widowed	7	12	4	14	5	5	8
	Socio-economic Class
	AB Managerial/professional	15	18	7*	21	7	6*	8
	C1 Supervisory	18	27*	28*	21	22	22	28
	C2 Skilled manual	29	27	35	30	29	19	31
	D Semi-skilled/unskilled manual	22	16	14	18	28	29	14
	E State pensioners/unemployed	17	12	15	11	15	24	20
	Religion
	Christian	64	9*	0.0*	0*	76*	36*	8*
	Hindu	0	56	0	0	0	0	0
	Sikh	0	17	0	0	0	0	0
	Muslim	0	18	100	100	0	64	0
	Other	4	0	0	0	0	0	35
	None	33	0	0	0	24	1	53
	Language
	English	100	57*	51*	67*	100	38*	27.5*
	Punjabi	0	17	13	0	0	0	0
	Hindi	0	9	0	0	0	0	0
	Gujarati	0	13	0	0	0	0	0
	Urdu	0	5	36	0	0	0	0
	Bangla	0	0	0	22	0	0	0
	Mandarin	0	0	0	0	0	0	73
	Somali	0	0	0	0	0	49	0
	Other	0	0	0	11	0	13	0
	Generational status
	2 nd generation	94	26*	15*	6*	35*	24*	28*
	1 st generation	6	32	54	48	29	36	33
	Immigrant	0	43	32	46	35	40	39
	P'stani=Pakistani, B'deshi=Bangladeshi, C'bbean=Caribbean
	Bold -

Table 2 : Univariate logistic regression analyses exploring predictors of HPV awareness (n=950) and acceptability of HPV vaccination (mothers only, n=601)

 2

			Awareness of HPV	Acceptability of HPV vaccination
		%	OR (95% CI)	P-value	%	OR (95% CI)	P-value
	Ethnicity
	White British	39	1.00		63	1.00
	Indian	9	0.15 (0.09-0.26)	<.001	25	0.20 (0.12-0.33)	<.001
	Pakistani	12	0.22 (0.13-0.38)	<.001	11	0.07 (0.04-0.14)	<.001
	Bangladeshi	6	0.11 (0.04-0.30)	<.001	18	0.13 (0.06-0.29)	<.001
	Caribbean	14	0.25 (0.14-0.45)	<.001	49	0.55 (0.32-0.98)	.040
	African	8	0.13 (0.08-0.27)	<.001	51	0.61 (0.33-1.10)	.102
	Chinese	18	0.34 (0.16-0.73)	.006	40	0.39 (0.18-0.87)	.022
	Age
	16-24	22	1.78 (1.08-2.93)	.024	17	0.38 (0.14-1.02)	.054
	25-34	18	1.42 (0.88-2.30)	.149	43	1.43 (0.94-2.16)	.091
	35-44	13	1.00		35	1.00
	45-54	19	1.55 (0.88-2.74)	.128	36	1.06 (0.63-1.77)	.834
	55+	11	0.81 (0.42-1.56)	.527	43	1.42 (0.87-2.32)	.167
	Marital status
	Married/Cohabitating	14	1.00		37	1.00
	Single	21	1.60 (1.09-2.33)	.015	36	0.95 (0.55-1.65)	.848
	Divorced/Separated/Widowed	23	1.65 (0.91-3.00)	.099	43	1.24 (0.68-2.28)	.480
	Socio-economic Class
	AB Managerial/professional	21	1.00		38	1.00
	C1 Supervisory	17	0.78 (0.44-1.38)	.400	34	0.81 (0.46-1.43)	.471
	C2 Skilled manual workers	16	0.74 (0.43-1.29)	.293	34	0.83 (0.48-1.42)	.486
	D Semi-skilled/unskilled manual workers	15	0.67 (0.37-1.22)	.187	38	0.98 (0.55-1.73)	.935
	E State pensioners/unemployed	16	0.73 (0.39-1.37)	.325	48	1.48 (0.83-2.66)	.187
	Religion
	None	18	1.00		64	1.00
	Christian	27	1.73 (1.02-2.93)	.043	53	0.61 (0.37-1.03)	.066
	Hindu	12	0.61 (0.30-1.24)	.173	34	0.28 (0.15-0.53)	<.001
	Muslim	10	0.51 (0.23-0.92)	.024	18	0.12 (0.07-0.21)	<.001
	Other	16	0.93 (0.42-2.05)	.855	17	0.12 (0.04-0.33)	<.001
	Language
	English	19	1.00		44	1.00
	Not English	11	0.52 (0.35-0.79)	.002	26	0.45 (0.31-0.65)	<.001
	Generational status
	2 nd generation	24	1.00		50	1.00
	1 st generation	14	0.51 (0.34-0.76)	.001	35	0.54 (0.36-0.80)	.002
	Immigrant	10	0.37 (0.23-0.57)	<.001	25	0.34 (0.22-0.51)	<.001
	Aware of HPV
	Yes	-	-	-	41	1.00
	No	-	-	-	37	0.83 (0.52-1.32)	.432

Table 3 : Reasons for HPV vaccine decision (percentage of mothers citing each reasons, n=601)

 3

		White	Indian	P'stani	B'deshi	C'bbean	African	Chinese
		(n=149)	(n=130)	(n=112)	(n=45)	(n=74)	(n=61)	(n=30)
	Reasons for accepting
	Protection	29	16*	11*	13*	14*	25	30
	Daughters health	9	6	5	2	16	7	7
	General positive	5	2	3	0	7	7	0
	Benefits	5	3	5	0	3	7	0
	Availability	3	1	0	0	3	0	3
	There is a necessity	2	1	1	0	1	0	0
	Responsibility	3	0	0	0	1	0	0
	Peace of mind	0	0	1	0	3	2	0
	Reasons for not-accepting
	More information	16	12	21	44*	18	10	20
	Sex related reasons	2	15*	20*	4	16	5	10
	Safety/side effects	7	12	6	13	5	5	3
	Religion/culture	5	8	6	0	3	7	3
	No necessity	0	8	5	2	0	2	0
	Age related reasons	1	2	1	4	1	3	0
	Trust	0	2	5	0	0	2	0
	Discuss with family	1	2	1	0	0	2	0
	P'stani=Pakistani, B'deshi=Bangladeshi, C'bbean=Caribbean

Table 4 : Fathers roles (column percentages)

 4 represents when a 2x2 chi-square was used to analyse whether the reason was cited more/less in that ethnic group compared to the white British group. * indicates a significant difference, p<.05

		White	Indian	P'stani	B'deshi	C'bbean	African	Chinese
		(n=149)	(n=130)	(n=112)	(n=45)	(n=74)	(n=61)	(n=30)
	I would take the lead role	64	31*	32*	18*	42*	32*	53
	We would decide together (50:50)	36	61*	57*	66*	56*	63*	30
	Her father would take the lead role	0	9*	10	16	3	5	17
	P'stani=Pakistani, B'deshi=Bangladeshi, C'bbean=Caribbean
	Bold -

Acknowledgements

This study was supported by Cancer Research UK. We thank the Department of Health for organising the translation of the HPV information presented to women in this study.

Competing interests

Jane Wardle has previously received funds for research and consultancy fees from Sanofi Pasteur MSD and GSK biologicals.

"The Corresponding Author has the right to grant on behalf of all authors and does grant on behalf of all authors, an exclusive licence (or non-exclusive for government employees) on a worldwide basis to the BMJ Publishing Group Ltd and its Licensees to permit this article (if accepted) to be published in Journal of Epidemiology and Community Health and any other BMJPGL products to exploit all subsidiary rights, as set out in our licence (http://jech.bmj.com/ifora/licence.pdf)"


Ylva Almquist
email: ylva.almquist@chess.su.se

Peer status in school and adult disease risk: A 30-year follow-up study of disease-specific morbidity in a Stockholm cohort

Keywords: Peer status, birth cohort, longitudinal, disease-specific, in-patient care

Background: Children have a social status position of their own, apart from that of the family, that may have an impact on short-term and long-term health. The aim of the present study was to analyse the associations between childhood social status in school, i.e. peer status, and disease-specific morbidity in adulthood.

Methods: Data was derived from a longitudinal study using a 1953 cohort born in Stockholm, Sweden: The Stockholm Birth Cohort Study (1953-2003). Peer status was sociometrically assessed in 6th grade (1966). Hazard ratios for adult disease-specific morbidity based on information on in-patient care (1973-2003) were calculated by peer status category for men and women separately, using Cox regression.

Results:

The results indicate that the lower the childhood peer status, the higher the overall adult disease risk. There were however differences in the degree and magnitude to which disease-specific in-patient care varied with peer status. Some of the steepest gradients were found for mental and behavioural disorders (e.g. alcohol abuse and drug dependence), external causes (e.g. suicide) and various lifestyle-related diseases (e.g. ischaemic heart disease and diabetes). The results were not explained by childhood social class.

Conclusion:

The present study underscores the importance of recognizing children's social position, apart from that of their family, for later health. Not only psychologically related diseases but also those related to behavioural risk factors demonstrate some of the largest relative differences by peer status, suggesting that health-related behaviour may be one important mechanism in the association between peer status and morbidity.

INTRODUCTION

The relationship between social position and health is well-established; it indicates that people in higher positions have better health and live longer than those in lower positions. [START_REF] Marmot | The status syndrome. How social standing affects our health and longevity[END_REF] While most studies tend to focus on one phase in life, some researchers have emphasised the contribution of socially-patterned exposures across the life course to health inequalities, thus stressing the need to adopt a life-course perspective on inequalities in health. [START_REF] Smith | Life-course approaches to socioeconomic differentials in cause-specific adult mortality, in Poverty inequality and health. An international perspective[END_REF][START_REF] Smith | Socioeconomic differentials, in A life course approach to chronic disease epidemiology[END_REF][START_REF] Smith | Down at heart -the meaning and implications of social inequalities in cardiovascular disease[END_REF][START_REF] Hallqvist | Can we disentangle life course processes of accumulation, critical period and social mobility? An analysis of disadvantaged socio-economic positions and myocardial infarction in the Stockholm Heart Epidemiology Program[END_REF][START_REF] Vågerö | Explaining health inequalities beyond Black and Barker[END_REF][START_REF] Lawlor | Association of childhood socioeconomic position with cause-specific mortality in a prospective record linkage study of 1,839,384 individuals[END_REF] This approach has commonly been used in studies which examine the relevance of social position in childhood for children's current and future health. [START_REF] Smith | Adverse socioeconomic conditions in childhood and cause specific adult mortality: prospective observational study[END_REF][START_REF] Osler | Socioeconomic position in early life, birth weight, childhood cognitive function, and adult mortality. A longitudinal study of Danish men born in 1953[END_REF][START_REF] Lawlor | Childhood socioeconomic position, educational attainment, and adult cardiovascular risk factors: The Aberdeen Children of the 1950s Cohort Study[END_REF][START_REF] Galobardes | Childhood socioeconomic circumstances and cause-specific mortality in adulthood: Systematic review and interpretation[END_REF][START_REF] Power | Socioeconomic position in childhood and early adult life and risk of mortality: A prospective study of the mothers of the 1958 British Birth Cohort[END_REF] Childhood social position is in most cases indicated by parents' occupational class, income or education. It has, nevertheless, been argued that children may have a social position of their own, apart from that of the family, that may have an impact on short-term and long-term health. [START_REF] Östberg | Status relations in school and their relevance for health in a life course perspective: Findings from the Aberdeen children of the 1950's cohort study[END_REF] Here, school is an important context, where children spend most of their waking hours, interacting with peers on a daily basis. In the school class, a hierarchical structure of social relations emerges, in which different positions represent varying degrees of 'peer status'. The notion of peer status refers to the degree of which the individual is an accepted, integrated and respected member of the group. [START_REF] Östberg | Status relations in school and their relevance for health in a life course perspective: Findings from the Aberdeen children of the 1950's cohort study[END_REF][START_REF] Östberg | Children in classrooms: Peer status, status distribution and mental wellbeing[END_REF] It also includes the recognition among peers of achieved prestige, visibility and reputation. [START_REF] Adler | Socialization to gender roles: Popularity among elementary school boys and girls[END_REF] Peer status is thus not only viewed as the degree of liking by peers, but also as a construct based on power and status in the group. [START_REF] Lease | Children's social constructions of popularity[END_REF][START_REF] Xie | Social networks and configurations in inner city schools: Aggression, popularity, and implications for student with EBD[END_REF] While associations between childhood peer status and a number of health outcomes in childhood have been found, [START_REF] Östberg | Children in classrooms: Peer status, status distribution and mental wellbeing[END_REF][START_REF] Due | Socioeconomic health inequalities among a nationally representative sample of Danish adolescents: the role of different types of social relations[END_REF][START_REF] Låftman | The pros and cons of social relations: An analysis of adolescents' health complaints[END_REF] less is known about the influence of peer status on adult health. [START_REF] Östberg | Status relations in school and their relevance for health in a life course perspective: Findings from the Aberdeen children of the 1950's cohort study[END_REF] It is, however, reasonable to suppose that peer status may have an impact on long-term health, possibly mediated through resources (e.g. emotional, material, and social), self-image, aspirations and expectations, as well as subsequent life choices (e.g. healthy versus non-healthy lifestyles). Thus, while the relationship between peer status and health may be interpreted as process of mutual influence that evolves over time, [START_REF] Hay | Peer relations in childhood[END_REF] there are good reasons to focus the influence of peer status on health. The health outcomes studied in relation to peer status hitherto have primarily concerned psychological health or self-reported health outcomes. The present study seeks to investigate the associations between childhood peer status and disease-specific types of morbidity in adulthood, using hospital discharge data. It will also examine whether these associations remain when parental social class is taken into account.

METHODS

The data material used is the Stockholm Birth Cohort Study, created in 2004/2005 by a probability matching of two longitudinal studies: The Stockholm Metropolitan Study (SMS) and The Swedish Work and Mortality Data Base (WMD). [START_REF] Stenberg | Stockholm Birth Cohort Study 1953-2003: A new tool for life-course studies[END_REF] The Metropolitan cohort comprised all children born in 1953 and living in the greater Stockholm metropolitan area in 1963 (n=15,117). The SMS-data covers the period 1953-1986, while the follow-up data from the WMD covers the period 1981-2003. Approximately 96 % (n=14,294) of the SMS cohort was matched successfully. Ethical permission was obtained from the Stockholm Regional Ethics Committee.

Peer status was measured in 6th grade, when the children were 12-13 years of age (1966). It was established by the question: "Whom in this class do you best like to work with at school?" This question includes dimensions of school performance as well as of friendship, likeability and social inclusion. For example, Stütz finds a high positive correlation between children's nominations of work partners and their nominations of best friends. [START_REF] Stütz | Kamratstatus[END_REF] All pupils were instructed to nominate three classmates in no particular order. School classes with less than 10 pupils were excluded from the analyses. The nominations were categorised into five status groups: marginalized (0 nominations), peripheral (1 nomination), accepted (2-3 nominations), popular (4-6 nominations), and favourite (7 or more nominations). [START_REF] Östberg | Children in classrooms: Peer status, status distribution and mental wellbeing[END_REF] This categorisation follows the recommendations that have been made for sociometric information based on three positive nominations, with the mean value as guideline. [START_REF] Stütz | Kamratstatus[END_REF] (For a further description, see [START_REF] Östberg | Status relations in school and their relevance for health in a life course perspective: Findings from the Aberdeen children of the 1950's cohort study[END_REF][START_REF] Östberg | Children in classrooms: Peer status, status distribution and mental wellbeing[END_REF] ) Because the status distribution does not vary systematically between school classes of different size, it is assumed that the categorisation of peer status reflects a child's relative standing in the school class irrespective of class size. [START_REF] Östberg | Children in classrooms: Peer status, status distribution and mental wellbeing[END_REF] Parental social class was included as a control variable. This information was derived from the 1963 Population Register and, in most cases, refers to the male head of the family. [START_REF] Janson | The school study -A code book[END_REF] The categories were: upper and upper middle class; entrepreneurs; officials and non-agricultural employees; skilled workers; unskilled workers and others (e.g. homemakers, pensioners and students). Information on overall morbidity (i.e. any event leading to in-patient care) was derived from the Swedish Hospital Discharge Register, covering the years 1973-2003. This register contains data about in-patient care, based on all discharges from Swedish hospitals (overnight patients). The diagnoses contained in these records are primarily based on the judgement of the doctor [START_REF] Weitoft | Is perceived nervousness and anxiety a predictor of premature mortality and severe morbidity? A longitudinal follow up of the Swedish survey of living conditions[END_REF] and classified using the 8th Revision (1973-1986), the 9th Revision (1987-1996) and the 10th Revision (1997-2003) of the International Classification of Diseases (ICD). In the present study, underlying diagnoses were grouped according to the European Shortlist for Causes of Death as established by Eurostat (see Spijker [START_REF] Spijker | Socioeconomic determinants of regional mortality differences in Europe[END_REF] for a further description). The shortlist was chosen not only to facilitate a meaningful grouping of diseases, but also to enable comparisons with similar previous studies (e.g. Erikson and Torssander's work on social class and cause-specific mortality [START_REF] Erikson | Social class and cause of death[END_REF] ). Since it focuses on causes of death, however, some important morbidity outcomes with low mortality (such as depression) are not identified. The shortlist is largely based on the ICD-chapters (although somewhat more compressed) and includes 65 hierarchically arranged groups, of which 17 constitute first-level groups and the rest second-level groups. [START_REF]Causes of death: 1994-1995 statistics[END_REF] In-patient care due to complications of pregnancy, childbirth and puerperium were not included in the present study. Furthermore, in-patient care due to certain conditions originating in the perinatal period, and for congenital malformations and chromosomal abnormalities, were excluded since they precede the establishment of peer status. For the analysis, individuals were first categorised into a dichotomous variable indicating overall in-patient care (i.e. the presence or the absence of a hospital discharge between 1973 and 2003, regardless of diagnosis). They were then categorised as discharged or not for all disease-specific groups respectively. Consequently, any given individual may appear in multiple groups. Although this must be kept in mind when interpreting the results, if only the very first event had been included (in line with previous studies analysing multiple years of hospital data [START_REF] Weitoft | Is perceived nervousness and anxiety a predictor of premature mortality and severe morbidity? A longitudinal follow up of the Swedish survey of living conditions[END_REF][START_REF] Weitoft | Mortality, severe morbidity, and injury in children living with single parents in Sweden: A population-based study[END_REF] ), this would firstly have disqualified diseases with a later onset and, secondly, resulted in several disease-groups not being large enough to analyse.

The study population was defined as those with full data for all included variables who attended a school class with at least 10 children, leaving 12,504 individuals eligible for analysis. The procedure of analysing the associations between peer status and cause-specific in-patient care was the following: first, associations between peer status and in-patient care were analysed using Cox's proportional hazards regression models, producing hazard ratios with the highest peer status group ('favourite') as the reference category. Subjects entered the study on 1973-01-01 and were censored when dying due to any disease, on the date of first discharge (for each disease-specific group separately) or at the end of follow-up (2003-12-31).

In both cases, only information on year is available; month of discharge or death is therefore set at the last day of June in the appropriate year. The issue of tied failures times has been handled by controlling the results through the exactm command in Stata; an exact marginallikelihood method that is appropriate when tied failures are numerous. In a second step, a summary measure of the size of the peer status differences was constructed, using a procedure adopted from Erikson and Torssander. [START_REF] Erikson | Social class and cause of death[END_REF] Slopes were calculated by means of OLS regressions of the logged parameter values of the five categories of peer status. These slopes were produced for each first-level, as well as for those second-level disease-specific groups which contained at least 30 discharges. The significance of the slopes (5 % level) is based on Kendall's rank order tests of the assumption of a monotonous increase in the hazard ratios from the highest peer status category to the lowest, as opposed to an assumption of no association. Finally, for comparative purposes, additional analyses of peer status and morbidity were conducted. Here, beta coefficients from Cox regressions, with peer status included as a continuous measure (i.e. number of nominations, ranging from 0-22), were calculated.

RESULTS

The hazard ratios for peer status and overall in-patient care (Table 1) demonstrate a clear gradient for men and women alike. This suggests that the lower the peer status, the higher the risk of overall in-patient care in adulthood. These associations remain when childhood social class is adjusted for. The slope is estimated at 0.0935 for men and 0.0928 for women, with a marginal decrease when parental social class is added to the analyses. Large differences by peer status are found in mental and behavioural disorders, and in the second-level groups alcohol abuse and drug dependence. For example, drug dependence demonstrates a very steep slope, both for men (0.24) and women (0.17). Second-level groups related to external causes of injury and poisoning, such as suicide and intentional self-harm, accidental poisoning and events of undetermined intent, also demonstrate steep gradients. For example, the slope for accidental poisoning is 0.44 for men and 0.23 for women.

Another finding concerns diseases of the circulatory system. Although there is no evident slope of this first-level group, the second-level groups ischaemic heart disease (IHD) and cerebrovascular diseases for men and women, as well as other heart diseases for women, show some of the steepest gradients of all the included disease-specific groups. For example, the slope for IHD is 0.46 for men and 0.29 for women. Slopes related to endocrine, nutritional and metabolic diseases are also very steep. For instance, the slope for diabetes is 0.26 for men and 0.18 for women.

Most of the remaining first-level groups demonstrate slopes in the range between 0.10 and 0.20. Some gender differences can be noted: for women, there is no observable slope for neoplasms (0.05) (which is not surprising, since breast cancer is more common among more highly-educated women [START_REF] Strand | The reversed social gradient: higher breast cancer mortality in the higher educated compared to lower educated. A comparison of 11 European populations during the 1990s[END_REF] ), while the opposite result is found for men (0.20). This pattern can also be observed for infectious and parasitic diseases and diseases of the genitourinary system. For diseases of the digestive system, however, the slope is fairly steep for women (0.13) but not for men (0.06). The same pattern is found for diseases of the skin and subcutaneous tissue. Finally, diseases of the blood(-forming) organs and immunological disorders demonstrate little evidence of slopes for men and women alike.

Beta coefficients from Cox regressions, with peer status included as a continuous measure, are presented in the last column of Table 2 (men) and Table 3 (women). Although these coefficients are based on a different scale than the slopes, the results are very similar (with only some exceptions) to the slopes based on the categorised peer status measure.

DISCUSSION

The results suggest that childhood social status in school is associated with overall adult morbidity leading to hospital care: the lower the peer status in school, the higher the risk of in-patient care in adulthood. This gradient exists for women and men alike. When in-patient care is divided into disease-specific groups, however, there are substantial differences in the degree and magnitude to which they vary with peer status, suggesting that peer status position in childhood is associated with most -but not all -types of morbidity. Thus, these findings are to some extent in line with theories of 'general susceptibility' among individuals in lower social positions, suggesting that there is a common set of general risk factors underlying the association between social position and health. [START_REF] Marmot | Inequalities in death -specific explanations of a general pattern?[END_REF] However, the variation in associations also emphasises the importance of interpreting the heterogeneous contributions in order to find the mechanisms and pathways through which peer status is linked to disease. [START_REF] Galobardes | Childhood socioeconomic circumstances and cause-specific mortality in adulthood: Systematic review and interpretation[END_REF] The gradient for mental and behavioural disorders (including depression, anxiety, alcohol abuse and drug use) and the large relative differences for external causes (such as suicide attempts and intentional self-harm) are consistent with results from previous studies. [START_REF] Cowen | Long-term follow-up of early detected vulnerable children[END_REF][START_REF] Roff | Childhood social adjustment, adolescent status, and young adult mental health[END_REF] For example, Östberg and Modin found an association between childhood peer status and selfreported health problems in adulthood. [START_REF] Östberg | Status relations in school and their relevance for health in a life course perspective: Findings from the Aberdeen children of the 1950's cohort study[END_REF] Despite the fact that the degree of severity most probably differs between diseases influencing self-reported health problems and diseases leading to in-patient care, the results from Östberg and Modin's study are quite similar to the results found in the present study. The most interesting finding in the present study, however, are the steep gradients for ischaemic heart disease and cerebrovascular diseases for men and women, other heart diseases for women, and diabetes. These types of disease are known to be socially patterned, [START_REF] Smith | Life-course approaches to socioeconomic differentials in cause-specific adult mortality, in Poverty inequality and health. An international perspective[END_REF][START_REF] Unwin | Journal of Epidemiology and Community Health[END_REF] and they have previously been linked to childhood socioeconomic status, but not to the child's status position in school. A plausible mechanism may involve lifestyle factors, health related behaviours, and perhaps stress. To verify this, further research is needed.

The results for peer status and disease-specific morbidity correspond quite well with previous analyses of adult social class and cause-specific mortality, [START_REF] Erikson | Social class and cause of death[END_REF] which may lead to the conclusion that peer status merely mediates the association between childhood socioeconomic status and morbidity. However, when parental social class is controlled for, the estimates are overall somewhat attenuated but the main findings remain unaltered. This suggests that the differences in morbidity by peer status are not accounted for by parental social class. Hence, although these types of status structure share important similarities inasmuch as they both are hierarchical structures of social position, there are also important differences due to the different structural levels on which these status positions are distributed. While the child's peer status position is created in the classroom (micro-level) thus directly affecting the child in everyday face-to-face interaction, childhood social status in society (macro-level) influences the child primarily via the parents. Thus, it may be assumed that psychosocial mechanisms (e.g. social support, social influence, and social engagement) are more directly linked to the former type of structure. [START_REF] Berkman | From social integration to health: Durkheim in the new millennium[END_REF] It has been suggested that these mechanisms influence health through three pathways: the psychological, the behavioural, and the physiological. [START_REF] Berkman | Social integration, social networks, social support, and health, in Social Epidemiology[END_REF] In the present study, some of the largest relative differences in diseasespecific morbidity by peer status were found in disease-specific groups that were psychologically related (e.g. mental disorders, suicide attempts and intentional self-harm) or affected by behavioural risk factors (e.g. diabetes and circulatory diseases such as ischaemic heart disease). [START_REF] Lawlor | Association of childhood socioeconomic position with cause-specific mortality in a prospective record linkage study of 1,839,384 individuals[END_REF] Hence, this study adds support to the notion of peer status being linked to health through behavioural and psychological pathways, and as such, influencing diseases with these particular kinds of aetiology. The results can also be seen as to support the physiological pathway, for instance, through obesity.

Peer status is here thought of as influencing morbidity, but one may argue that diseases that may have an early onset, such as mental disorders, precede the establishment of peer status.

Previous studies have, however, found that peer status predicts depressive symptoms irrespective of symptoms at an earlier point in time. [START_REF] Keisner | Depressive symptoms in early adolescence: Their relations with classroom problem behavior and peer status[END_REF] Nevertheless, peer status and health are perhaps best seen as parts of a process of mutual influence, evolving over time. [START_REF] Hay | Peer relations in childhood[END_REF] In a similar way, peer status appears to be continuously renegotiated. Status mobility is however restrained, particularly for individuals in the lowest and highest peer status positions. [37] Thus, one may assume that the assignment of social positions in the peer status hierarchy is a fairly stable phenomenon. To the extent that peers constitute significant others, [START_REF] Mead | self and society[END_REF] the exposure to expectations and access to resources that accompany any given peer status position are likely to have a long-term impact on the child's identity, behaviour, and ambitions, as well as the choices they make for themselves. This may in turn affect health development across the life course.

Few data materials permit a life-course approach to peer status in school and morbidity. The Stockholm Birth Cohort study used in this paper offers the opportunity to examine how sociometrically-assessed childhood peer status in ages 12-13 relates to a wide variety of morbidity outcomes from ages 20 to 50. The present study does, however, have some important limitations. First, the use of hospital discharge register data to indicate morbidity produces a possible bias if status position in school also predicts differences in help-seeking behaviour. Second, the cohort members are relatively young, meaning that diseases with a late onset are not well represented, which precludes the analysis of some second-level disease groups (e.g. types of cancer). A somewhat different overall picture may have emerged if it had been possible to include all second-level groups. A third issue concerns comorbidity. For instance, alcohol-related disorders co-occur with other psychiatric disorders such as anxiety and depression, [START_REF] Burns | Alcohol use disorders comorbid with anxiety, depression and drug use disorders. Findings from the Australian National Survey of Mental Health and Well Being[END_REF] as well as with external causes such as suicide attempts. [START_REF] Beautrais | Prevalence and comorbidity of mental disorders in persons making serious suicide attempts: a case-control study[END_REF][START_REF] Henriksson | Mental disorders and comorbidity in suicide[END_REF] In addition, heart disease commonly co-occurs with diabetes. [START_REF] Simpson | The cost of major comorbidity in people with diabetes mellitus[END_REF] To complicate matters further, diabetes and heart diseases have been found to co-occur with depression, [START_REF] Anderson | The prevalence of comorbid depression in adult with diabetes[END_REF][START_REF] Gurbel | Depression and ischemic heart disease. Depression as a risk factor for cardiovascular and cerebrovascular disease[END_REF] schizophrenia, [START_REF] Dixon | Prevalence and correlates of diabetes in national schizophrenia samples[END_REF] and anxiety. [START_REF] Barger | Does generalized anxiety disorder predict coronary heart disease risk factors independently of major depressive disorder?[END_REF] Thus, one may claim that a small group of comorbid individuals account for a large proportion of disease. [START_REF] Erikson | Social class and cause of death[END_REF] As a consequence they contribute to the gradients in a wide range of diseases, equalizing differences in the magnitude of the effect of peer status between various diseases and leading to an overestimation of the results. When controlling for comorbid diseases in the analysis by including dummies, however, the associations between peer status and health-related diseases, and between peer status and psychologically related diseases, were reduced but only to a limited extent. Thus, the main findings remained unaltered (data not presented). Furthermore, if the association between peer status and morbidity was due to such circumstances, we would probably see a threshold effect for the marginalized group rather than a gradient across all peer status categories.

In conclusion, the results of this study, especially with regard to peer status being associated with such a wide range of morbidity outcomes, underscore the need to understand how and why peer status has such a seemingly strong impact on health outcomes across the life course. This is an important area of research and policy making, given that most children attend school for several years and are thus subjected to the social ordering of this micro-level social world. However, if the universality of status distributions constitutes 'a social law', [START_REF] Moreno | Who shall survive? Foundations of sociometry, group psychotherapy and sociodrama[END_REF] which seems to be the case, we should maybe rather focus on how the psychosocial mechanisms between social status in school and health operate, and how they may be influenced in order to reduce the negative impact of peer status on health across the life course.

WHAT THIS PAPER ADDS

What is already known on this subject?

In studies of childhood social status, parents' social position has proved to be related to the children's adult health, but only a small number of studies have considered the importance of the child's own social position in school; peer status. These studies have found an association between childhood peer status and future psychological health outcomes, as well as between peer status and self-reported health in adulthood.

What does this study add?

This study adds new knowledge by demonstrating that there is a gradient for various types of objectively measured morbidity in adulthood by childhood peer status. The latter effects not only psychological health, but also lifestyle related diseases, and in particular circulatory diseases.

Table 1 .

 1 The distribution of men (n=6,195) and women (n=6,309) in different peer status positions. Hazard ratios (HR) from Cox regression for overall in-patient care(1973-2003) by peer status (1966). Statistically significant hazard ratios (95 % CI) in boldface. Slopes in boldface are significant (95 % CI) according to rank correlation tests.

		Men	Women
	Peer status	Frequency (%)

Crude HR (95 % CI) Adjusted* HR (95 % CI) Frequency (%) Crude HR (95 % CI) Adjusted* HR (95 % CI) Marginalized

				44)	2470 (39.2) 1.14 (0.99-1.32) 1.12 (0.97-1.30)
	Popular	1547 (25.0) 1.13 (0.97-1.32) 1.11 (0.95-1.29)	1542 (24.4) 1.05 (0.90-1.23) 1.05 (0.90-1.23)
	Favourite (ref.)	432 (7.0)	1.00	1.00	344 (5.5)	1.00	1.00
	Total	6195 (100.0)			6309 (100.0)
	Slope		0.0935	0.0830		0.0928	0.0851

813 (13.1) 1.

47

(1.25-1.74) 1.41 (1.19-1.66) 607 (9.7) 1.41 (1.19-1.67) 1.37 (1.16-1.62) Peripheral 1205 (19.5) 1.33 (1.13-1.56) 1.28 (1.09-1.50) 1346 (21.3) 1.34 (1.15-1.56) 1.31 (1.13-1.53) Accepted 2198 (35.5) 1.28 (1.10-1.49) 1.24 (1.07-1.

* Adjusted for parental social class.

Table 2 (

 2 men) and Table3(women) present hazard ratios from Cox regressions for the disease-specific groups, sorted according to slope size. First-level and second-level disease groups are shown separately. Based on the results of the rank order tests, it is shown that linearity can be assumed, with only a few exceptions, for the relationship between peer status and the various disease-specific groups.

Table 2 .

 2 Hazard ratios (HR) from Cox regression of overall and disease-specific in-patient care(1973-2003) by peer status (1966) for men born in1953 (n=6,195). Both firstlevel and second-level groups (with at least 30 discharges) are shown. Hazard ratios significantly different from those for the favourite group (reference group, HR=1.00) in boldface. Slopes in boldface are significant at the 5 % level according to rank correlation tests.

	Disease-specific group (Eurostat number)	No. of cases (i.e. discharges)	Popular	Accepted	Peripheral	Marginalized Slope	B. Coeff.
	First-level groups
	Diseases of the blood(-forming organs) immunological disorders (25)	36	0.35 (0.09-1.29)	0.44 (0.13-1.43)	1.25 (0.41-3.81)	0.53 (0.13-2.11)	-0.04	0.12
	Diseases of the circulatory system (33)	249	0.79 (0.46-1.33)	0.86 (0.52-1.41)	0.92 (0.54-1.56)	1.20 (0.69-2.06)	0.04	0.05
	Diseases of the digestive system (42)	820	1.13 (0.82-1.55)	1.28 (0.94-1.73)	1.21 (0.87-1.67)	1.26 (0.90-1.77)	0.06	0.04
	Diseases of the skin and subcutaneous tissue (45)	174	0.86 (0.43-1.69)	1.20 (0.63-2.26)	1.07 (0.54-2.12)	1.40 (0.69-2.79)	0.09	0.07
	External causes of injury and poisoning (58)	1075	1.08 (0.81-1.42)	1.19 (0.91-1.55)	1.33 (1.01-1.76)	1.53 (1.14-2.04)	0.10	0.06
	Diseases of the genitourinary system (48)	212	1.17 (0.62-2.18)	1.15 (0.62-2.11)	1.29 (0.67-2.43)	1.65 (0.85-3.16)	0.11	0.07
	Diseases of the respiratory system (37)	520	1.15 (0.75-1.74)	1.41 (0.94-2.10)	1.40 (0.91-2.13)	1.77 (1.15-2.72)	0.14	0.08
	Symptoms, signs, abnormal findings, ill-def. causes (55)	821	1.24 (0.88-1.74)	1.39 (1.01-1.93)	1.63 (1.16-2.29)	1.83 (1.29-2.60)	0.15	0.08
	Infectious and parasitic diseases (1)	372	1.51 (0.88-2.58)	1.53 (0.90-2.57)	1.96 (1.15-3.34)	2.06 (1.18-3.56)	0.17	0.09
	Diseases of the musculoskeletal system/connective tissue (46)	523	1.46 (0.92-2.30)	1.70 (1.09-2.63)	1.98 (1.25-3.11)	1.98 (1.23-3.17)	0.17	0.08
	Neoplasms (6)	178	1.52 (0.67-3.39)	1.64 (0.74-3.58)	2.43 (1.09-5.36)	2.14 (0.93-4.90)	0.20	0.12
	Diseases of the nervous system and the sense organs (31)	270	1.57 (0.80-3.08)	1.99 (1.03-3.80)	2.25 (1.15-4.38)	2.26 (1.13-4.50)	0.20	0.11
	Mental and behavioural disorders (28)	559	1.28 (0.82-1.99)	1.58 (1.02-2.40)	2.23 (1.44-3.43)	2.17 (1.38-3.39)	0.20	0.12
	Endocrine. nutritional and metabolic diseases (26)	131	2.39 (1.04-10.9)	2.37 (0.72-7.68)	3.86 (1.18-12.6)	4.30 (1.19-14.2)	0.31	0.12
	Second-level groups
	Transport accidents (60)	521	0.74 (0.52-1.04)	0.53 (0.54-1.04)	0.79 (0.55-1.12)	1.00 (0.69-1.43)	0.00	0.02
	Other heart diseases (35)	124	0.94 (0.42-2.06)	1.20 (0.56-2.53)	1.07 (0.48-2.38)	1.06 (0.45-2.47)	0.03	0.03
	Diseases of kidney and ureter (49)	106	0.66 (0.28-1.51)	0.88 (0.41-1.90)	1.16 (0.52-2.56)	1.13 (0.48-2.61)	0.07	0.09
	Accidents (59)	993	1.01 (0.75-1.33)	1.14 (0.86-1.49)	1.29 (0.96-1.71)	1.42 (1.05-1.90)	0.09	0.06
	Cerebrovascular diseases (36)	74	0.98 (0.32-2.96)	1.38 (0.48-3.92)	1.35 (0.44-4.06)	1.73 (0.56-5.30)	0.14	0.09
	Events of undetermined intent (65)	185	0.78 (0.37-1.60)	1.56 (0.80-3.01)	1.29 (0.64-2.60)	1.71 (0.84-3.48)	0.16	0.09
	Alcohol abuse (including alcoholic psychosis) (29)	222	1.18 (0.59-2.34)	1.50 (0.77-2.90)	1.92 (0.97-3.77)	2.21 (1.10-4.41)	0.20	0.14
	Pneumonia (39)	109	0.70 (0.27-1.79)	1.45 (0.61-3.39)	1.14 (0.45-2.85)	2.24 (0.91-5.45)	0.21	0.14
	Malignant neoplasms (7)	105	1.40 (0.47-4.09)	1.58 (0.55-4.45)	2.88 (1.01-8.15)	2.27 (0.76-6.74)	0.23	0.14
	Drug dependence, toxicomania (30)	185	1.17 (0.47-2.84)	2.01 (0.87-4.65)	3.47 (1.49-8.04)	3.24 (1.36-7.70)	0.24	0.23
	Diabetes mellitus (27)	76	2.67 (0.62-11.4)	2.46 (0.58-10.3)	3.24 (0.75-13.9)	3.20 (0.71-14.3)	0.26	0.11
	Suicide and intentional self-harm (63)	99	3.51 (0.83-14.8)	3.56 (0.85-14.7)	3.79 (0.88-16.1)	4.01 (0.91-17.5)	0.30	0.20
	Accidental poisoning (62)	132	2.94 (0.68-12.5)	4.96 (1.20-20.3)	7.09 (1.71-29.3)	5.36 (1.25-22.9)	0.44	0.23
	Ischaemic heart diseases (34)	84	5.90 (0.79-43.8)	7.73 (0.78-42.8)	5.76 (0.76-43.4)	9.10 (1.21-68.4)	0.46	0.15
	Overall in-patient care	3311	1.13 (0.97-1.32)	1.28 (1.10-1.49)	1.33 (1.13-1.56)	1.47 (1.25-1.74)	0.0935	0.0487

Table 3 .

 3 Hazard ratios (HR) from Cox regression of overall and disease-specific in-patient care(1973-2003) by peer status (1966) for women born in 1953 (n=6,309). Both first-level and second-level groups (with at least 30 discharges) are shown. Hazard ratios significantly different from those for the favourite group (reference group, HR=1.00) in boldface. Slopes in boldface are significant at the 5 % level according to rank correlation tests.

	Disease-specific group (Eurostat number)	No. of cases (i.e. discharges)	Popular	Accepted	Peripheral	Marginalized Slope	B. Coeff.
	First-level groups
	Diseases of the blood(-forming organs) immunological disorders (25)	64	0.50 (0.15-1.63)	1.05 (0.36-2.97)	0.96 (0.31-2.89)	0.85 (0.24-3.02)	0.04	0.06
	Infectious and parasitic diseases (1)	449	0.76 (0.48-1.17)	0.97 (0.64-1.46)	0.99 (0.64-1.53)	1.12 (0.69-1.79)	0.05	0.05
	Neoplasms (6)	876	0.77 (0.56-1.04)	0.89 (0.66-1.19)	1.00 (0.73-1.35)	1.04 (0.74-1.45)	0.05	0.04
	Diseases of the genitourinary system (48)	1472	0.88 (0.68-1.13)	1.09 (0.85-1.38)	1.16 (0.90-1.49)	1.25 (0.95-1.63)	0.07	0.05
	Diseases of the circulatory system (33)	225	0.93 (0.47-1.78)	1.17 (0.62-2.19)	1.09 (0.56-2.10)	1.45 (0.71-2.90)	0.08	0.08
	External causes of injury and poisoning (58)	702	0.91 (0.62-1.33)	1.00 (0.69-1.43)	1.15 (0.78-1.67)	1.42 (0.95-2.13)	0.09	0.06
	Diseases of the nervous system and the sense organs (31)	285	0.84 (0.46-1.51)	1.21 (0.69-2.10)	1.13 (0.63-2.02)	1.43 (0.76-2.65)	0.09	0.09
	Diseases of the respiratory system (37)	519	1.09 (0.68-1.71)	1.25 (0.80-1.94)	1.68 (1.07-2.63)	1.35 (0.82-2.22)	0.10	0.07
	Diseases of the digestive system (42)	861	1.56 (1.05-2.30)	1.65 (1.12-2.40)	1.87 (1.26-2.75)	1.96 (1.29-2.97)	0.13	0.08
	Endocrine. nutritional and metabolic diseases (26)	200	1.07 (0.54-2.13)	0.94 (0.42-1.63)	1.32 (0.66-2.59)	1.79 (0.87-3.65)	0.13	0.09
	Symptoms, signs, abnormal findings, ill-def. causes (55)	1070	1.03 (0.74-1.40)	1.21 (0.89-1.63)	1.47 (1.07-2.00)	1.87 (1.34-2.60)	0.15	0.10
	Diseases of the musculoskeletal system/connective tissue (46)	163	0.94 (0.58-1.53)	1.22 (0.76-1.94)	1.54 (0.95-2.47)	1.83 (1.10-3.02)	0.15	0.11
	Mental and behavioural disorders (28)	483	1.14 (0.76-2.08)	1.36 (0.83-2.20)	1.84 (1.12-3.00)	2.05 (1.21-3.45)	0.16	0.11
	Diseases of the skin and subcutaneous tissue (45)	163	1.34 (0.51-3.45)	1.79 (0.71-4.43)	2.31 (0.91-5.82)	2.16 (0.80-5.78)	0.18	0.11
	Second-level groups
	Transport accidents (60)	268	0.66 (0.39-1.11)	0.75 (0.45-1.22)	0.76 (0.45-1.27)	0.95 (0.53-1.67)	0.01	0.03
	Malignant neoplasms (7)	283	0.66 (0.39-1.08)	0.77 (0.47-1.23)	0.77 (0.46-1.27)	0.97 (0.55-1.68)	0.02	0.03
	Pneumonia (39)	117	0.70 (0.29-1.63)	0.85 (0.38-1.89)	1.31 (0.58-2.95)	0.72 (0.26-1.94)	0.02	0.03
	Accidents (59)	542	0.79 (0.52-1.17)	0.92 (0.63-1.34)	1.03 (0.69-1.53)	1.25 (0.81-1.91)	0.07	0.06
	Diseases of kidney and ureter (49)	153	0.93 (0.40-2.12)	1.32 (0.60-2.88)	1.14 (0.50-2.58)	1.64 (0.69-3.86)	0.10	0.07
	Alcohol abuse (including alcoholic psychosis) (29)	117	0.78 (0.31-1.93)	0.95 (0.40-2.24)	1.63 (0.68-3.85)	1.04 (0.38-2.82)	0.12	0.10
	Drug dependence, toxicomania (30)	117	0.63 (0.24-1.59)	1.07 (0.45-2.50)	1.23 (0.51-2.97)	1.81 (0.72-4.52)	0.17	0.14
	Cerebrovascular diseases (36)	44	2.01 (0.25-15.8)	2.65 (0.35-19.7)	2.56 (0.32-19.9)	2.84 (0.33-24.2)	0.18	0.08
	Diabetes mellitus (27)	57	1.68 (0.38-7.33)	1.19 (0.27-5.13)	1.54 (0.34-6.86)	3.15 (0.69-14.1)	0.18	0.09
	Suicide and intentional self-harm (63)	68	0.44 (0.11-1.77)	1.53 (0.47-5.00)	1.53 (0.45-5.20)	1.51 (0.40-5.70)	0.19	0.15
	Other heart diseases (35)	57	0.89 (1.18-4.19)	1.81 (0.43-7.64)	1.15 (0.24-5.32)	3.43 (0.76-15.3)	0.22	0.17
	Accidental poisoning (62)	117	1.28 (0.44-3.70)	1.25 (0.44-3.51)	2.31 (0.82-6.49)	2.56 (0.86-7.56)	0.23	0.15
	Events of undetermined intent (65)	68	3.12 (0.41-23.7)	3.91 (0.53-28.7)	3.84 (0.50-29.1)	5.70 (0.72-44.5)	0.29	0.10
	Ischaemic heart diseases (34)	35	1.11 (0.13-9.55)	1.95 (0.25-14.8)	2.04 (0.25-16.3)	3.99 (0.49-32.4)	0.29	0.25
	Overall in-patient care	3944	1.05 (0.90-1.23)	1.14 (0.99-1.32)	1.34 (1.15-1.56)	1.41 (1.19-1.67) 0.0928	0.0496

ACKNOWLEDGEMENTS

I am grateful for the permission to use the Stockholm Birth Cohort Study. The creation and maintenance of the Stockholm Birth Cohort Data Base is a collaboration between CHESS and SOFI, financed by the Swedish Research Council. Sten-Åke Stenberg of SOFI prepared the original Metropolitan Data Base, Denny Vågerö of CHESS prepared the follow-up data for 1980-2002, and Reidar Österman of CHESS organised the probability matching of the two data sets. I would also like to thank Jenny Torssander and Michael Gähler at SOFI as well as Denny Vågerö, Kristiina Rajaleid and Viveca Östberg at CHESS, for valuable comments.

FUNDING

This study was financially supported by the Swedish Council for Working Life and Social Research and the Swedish Research Council.

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