Background
Eating disorders (EDs) are severe psychiatric disorders associated with high levels of morbidity [
1], mortality [
2,
3], and social, psychological and physical impairment [
4]. The Diagnostic and Statistical Manual for Mental Disorders 5
th edition (DSM-5) [
5] recently broadened ED diagnostic criteria, aiming to reduce the number of individuals with an ED who do not fit full-threshold diagnostic categories. Binge-eating disorder (BED) was introduced as a diagnostic category, and the criteria for anorexia nervosa (AN) and bulimia nervosa (BN) were broadened. Although previously considered low prevalence disorders, this broadening of the diagnostic criteria in DSM-5 has yielded preliminary evidence that ED are more common than once thought. A small number of community-based studies have investigated the prevalence of DSM-5 EDs. Lifetime prevalence estimates of DSM-5 EDs have varied dramatically across studies [
6,
7] and the same applies to period-prevalence estimates [
8,
9]. The remarkable variability across studies is likely due to sample size, differences in study design (questionnaire only assessment vs. two-phase studies), and a focus on adolescents/young adults only (reflecting the peak age of onset of AN and BN), thus highlighting a need for further large studies. No previous studies have investigated the period or lifetime prevalence of EDs amongst women in the fourth and fifth decade of life, after most individuals would be considered to have passed through the primary window of risk. We recently highlighted a wide gap in access to healthcare amongst adults with ED in a UK population-based sample [
8], and we therefore sought to replicate and extend our findings.
A long-term perspective offers the unique opportunity to investigate EDs and relevant precursors/risk factors using a disease life-course approach. Few studies have investigated risk factors for EDs using a longitudinal prospective design [
10], and the majority have focused on treatment seeking samples and full threshold EDs. Prior evidence from our group [
11,
12] and others [
13,
14] points to childhood experiences and personality as important risk factors for EDs; however, there is a relative lack of population-based studies investigating these in relation to ED. Thus, our aims were (1) to determine the lifetime and 12-month prevalence of DSM-5 EDs in mid-life in women from a population-based cohort using a two-phase design and to explore healthcare access, as well as (2) to investigate associations between lifetime ED, risk factors (personality characteristics (personality, locus of control); early childhood experiences (sexual abuse, maternal care, carer/parent death, parental separation/divorce and being under local authority care)) and fixed factors (intelligence quotient (IQ)).
Results
Phase 1
Amongst women who were sent a questionnaire, 5655 (61.3%) returned completed questionnaires and 826 (14.88%) were screen positive. Amongst 4832 screen negative women, 698 (12%) were randomly selected for interview in Phase 2. Characteristics of participants in Phase 1 are shown in Additional file
1: Table S2; women who participated were more likely to have received secondary education and less likely to have had prior pregnancies. The prevalence of self-reported ED at enrolment (in pregnancy) did not differ. The average age of women who participated in the study was 47.78 years (SD: 4.5).
Phase 2
Amongst the 1524 women selected for interview, 1043 (68.4%) consented to participate in Phase 2 and were interviewed. Of those not interviewed, 10 were, at the time of interview, considered ineligible for participation by the ALSPAC study team (i.e., experiencing major life difficulties of a kind that made participation not possible such as bereavement and severe physical illness in the family), 29 (1.9%) declined participation and 442 (29.1%) were not contactable. One woman withdrew consent for participation in ALSPAC following interview, she was therefore excluded from all analyses. Interview data were therefore available for 1042 women.
Women who were interviewed within each stratum (screen positive or negative) did not differ on socio-demographic (parity, pre-pregnancy BMI, age, education) and screening (weight and shape concern, binge-eating, compensatory behaviors) characteristics from those not interviewed.
Prevalence of ED
Table
1 presents the lifetime and 12-month weighted prevalence of ED. The weighted lifetime prevalence of ED was 15.33% (95% CI, 13.48–17.42%) and the 12-month prevalence was 3.61% (3.00–4.35%). Amongst full threshold disorders, DSM-5 AN was the most common lifetime ED (3.64%). OSFED was highly prevalent, affecting 7.64% of women in their lifetime. EDs were common in the 12 months prior to assessment (weighted prevalence: 3.61%); BED was the most common full-threshold disorder (1.03%). New onset EDs represented 41.6% of 12-month prevalent diagnoses.
Table 1
Weighted lifetime and 12-month prevalence of eating disorders amongst 5542 participants
Any eating disorder | 332 | 15.33 (13.48–17.42) | 108 | 3.61 (3.00–4.35) |
Anorexia nervosa (all) | 105 | 3.64 (2.81–4.72) | 7 | 0.23 (0.16–0.47) |
Anorexia nervosa restrictive | 51 | 2.05 (1.40–3.01) |
Anorexia nervosa binge-purge | 54 | 1.68 (1.28–2.21) |
Bulimia nervosa | 68 | 2.15 (1.70–2.74) | 14 | 0.41 (0.24–0.70) |
Binge eating disorder | 62 | 1.96 (1.52–2.51) | 33 | 1.03 (0.73–1.46) |
OSFED (all) | 211 | 7.64 (6.32–9.24) | 56 | 1.65 (1.26–2.17) |
Purging disorder | 36 | 1.28 (0.85–1.92) | 7 | 0.23 (0.11–0.47) |
Sub-threshold bulimia nervosa | 46 | 1.42 (1.06–1.90) | 14 | 0.44 (0.27–0.74) |
Sub-threshold binge eating disorder | 30 | 0.90 (0.63–1.30) | 13 | 0.38 (0.22–0.67) |
Atypical anorexia nervosa | 51 | 1.70 (1.22–2.39) | 12 | 0.35 (0.20–0.63) |
Other OSFED | 49 | 2.14 (1.43–3.22) | 10 | 0.29 (0.16–0.55) |
Median age of onset for the first ED diagnosis was lowest for AN-R (16, range 11–39) and highest for sub-threshold BED (26, range 13–44). The majority of women (76.3%) reported the onset of their ED to be prior to the birth of the index child. Only 27.4% of all women with EDs had sought help or received treatment for an ED at any point in their life. The most common healthcare service use was having seen a general practitioner (8.2%); 4 (1.2%) women reported having seen a psychiatrist for their ED and 4 (1.2%) having received inpatient treatment; 16 (4.9%) women reported having received individual psychological treatment for their ED; and 13 (4.0%) reported having received psychological treatment for another disorder.
Risk factors
Amongst early risk factors, differences emerged across EDs. Having experienced death of a carer was associated with seven-fold increased odds for PD. Parental separation or divorce in childhood was associated with increased odds for BN, BED, and atypical AN. Child sexual abuse was associated with all disorders with binge-eating behaviors (anorexia nervosa binge-purge (AN-BP), BN, BED, and sub-threshold BN and BED) (Table
2). Sexual abuse perpetrated by a non-stranger was two-fold more prevalent amongst women with AN-BP, but as prevalent as sexual abuse by a stranger for BN and BED.
Table 2
Adjusted aassociations between eating disorders, bcorrelates and precursors amongst 5320 women: OR (95% CI) from multivariable logistic regression and mean differences (95% CI) from weighted multivariable linear regression
Risk factors | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) |
Adopted or taken into care | (N = 27) | (N = 40) | | (N = 59) | (N = 19) | | (N = 27) | | (N = 26) |
– | 2.35 (0.59–9.28) | 0.44 (0.06–3.39) | 1.43 (0.40–5.19) | – | 1.27 (0.16–9.88) | 0.79 (0.09–7.19) | – | 0.73 (0.01–6.01) |
Death of carer | | (N = 42) | | | | | | | |
0.83(0.22–3.16) | 0.99 (0.28–3.48) | 1.16 (0.44–3.10) | 1.72 (0.71–4.13) | 1.31 (0.26–6.69) | 0.59 (0.1–5.48) | 2.27 (0.68–7.59) | 2.27 (0.62–8.32) | 7.12** (2.32–21.85) |
Parental separation or divorce | | (N = 40) | | | (N = 20) | | | | |
2.51(0.83–7.58) | 1.06 (0.42–2.66) | 2.02* (1.10–3.75) | 2.01* (1.06–3.83) | – | 1.45 (0.41–5.07) | 2.49* (1.02–6.05) | 0.25 (0.03–2.05) | 0.85 (0.31–2.25) |
Child sexual abuse (any) | (N = 28) | | (N = 54) | (N = 59) | | | (N = 27) | (N = 17) | (N = 25) |
1.83 (0.72–4.65) | 3.81*** (1.95–7.43) | 4.70*** (2.60–8.50) | 3.42*** (1.95–5.99) | 3.23* (1.30–8.00) | 8.11*** (2.74–23.94) | 2.16 (0.90–5.15) | 3.11 (0.77–12.60) | 1.88 (0.79–4.48) |
Childhood unhappiness | | | (N = 54) | | | | | | |
2.52*** (1.19–5.34) | 1.95 (0.87–4.38) | 4.58*** (2.56–8.20) | 3.66*** (2.01–6.68) | 1.61 (0.50–5.16) | 1.91 (0.52–6.96) | 1.92 (0.70–5.25) | 2.97 (0.98–8.99) | 2.65* (1.17–6.00) |
Weighted life event score | (N = 29) | (N = 42) | | (N = 60) | (N = 22) | | | | (N = 26) |
1.05* (1.01–1.09) | 1.06*** (1.03–1.08) | 1.08*** (1.05–1.11) | 1.08*** (1.05–1.11) | 1.04* (1.00–1.07) | 1.06** (1.02–1.11) | 1.10*** (1.06–1.14) | 1.01 (0.95–1.08) | 1.04* (1.00–1.08) |
Parental bonding |
Maternal care | | (N = 42) | (N = 55) | | | | | | |
Top quartile | 0.75 (0.52–1.09) | 0.84 (0.70–1.02) | 0.79* (0.67–0.94) | 0.90 (0.77–1.05) | 0.76 (0.56–1.04) | 0.85 (0.60–1.19) | 1.09 (0.88–1.35) | 1.17 (0.83–1.64) | 0.94 (0.72–1.24) |
Bottom quartile | 1.83 (0.87–3.82) | 1.62 (0.75–3.51) | 2.30* (1.26–4.20) | 1.95* (1.03–3.68) | 0.99 (0.28–3.6111) | 6.73*** (2.32–19.54) | 1.72 (0.63–4.65) | 1.69 (0.53–5.41) | 3.40* (1.52–7.58) |
Parental overprotection | 1.01 (0.94–1.10) | 1.09* (1.02–1.16) | 1.08* (1.01–1.16) | 1.13** (1.05–1.21) | 1.13** (1.05–1.23) | 1.02 (0.86–1.21) | 1.12* (1.02–1.23) | 1.10 (0.93–1.31) | 1.19*** (1.10–1.29) |
Locus of control | 1.05 (0.92–1.20) | 1.17 (0.99–1.38) | 1.05 (0.93–1.20) | 1.19* (1.01–1.39) | 1.20 (0.89–1.62) | 1.10 (0.85–1.43) | 1.15 (0.92–1.43) | 1.11 (0.85–1.43) | 1.11 (0.93–1.33) |
Interpersonal sensitivity | | | (N = 56) | | | | | | (N = 26) |
1.05* (1.02–1.08) | 1.05*** (1.03–1.07) | 1.06*** (1.04–1.08) | 1.04*** (1.02–1.06) | 1.03** (1.01–1.05) | 1.04* (1.01–1.07) | 1.04** (1.02–1.07) | 0.98 (0.94–1.02) | 1.02 (0.99–1.04) |
Fixed factors |
WASI total IQ scorec
| 1.01 (0.97–1.05) | 1.04* (1.01–1.07) | 1.02 (0.99–1.05) | 1.02 (0.98–1.06) | 1.02 (0.97–1.07) | 1.04 (0.97–1.10) | 1.01 (0.95–1.07) | 0.97 (0.93–1.01) | 1.02 (0.97–1.06) |
Childhood unhappiness was associated with higher odds of AN-R, BN, BED, and PD. Childhood life events were positively associated with all ED (apart from other OSFED), with a 4–10% increased odds per unit score increase (Table
2). Reporting low maternal warmth (lowest quartile) was also associated with increased odds for BN, BED, and sub-threshold BED and PD. In contrast, women reporting high maternal warmth (top quartile) had 20% decreased odds of developing BN compared to those in the lowest 75% range. Women who reported a more oppressive relationship with parents had higher odds of AN-BP, BED, sub-threshold BN, atypical AN, and PD (Table
2). Amongst personality characteristics, a more external LOC was positively associated with BED, with a 19% increase in odds per one-point score increase. Higher levels of interpersonal sensitivity were positively associated with all EDs (apart from other OSFED and PD) (Table
2).
A marginal association was identified between higher total IQ and lifetime AN-BP, with a one-point increase in total IQ increasing the odds of AN-BP by 4% (OR = 1.04, 95% CI, 1.01–1.07).
Sensitivity analyses showed that, when analyses were restricted to women who had not transitioned to a different ED, the identified associations with risk factors did not change in magnitude or significance apart from the associations between maternal care and BN and BED becoming smaller and non-significant. Sensitivity analyses stratifying according to whether the ED disorder had onset before birth of the index child or after showed no differences in magnitude of associations apart from a smaller association between life events and AN-BP.
Discussion
In this large sample of UK women in mid-life DSM-5 EDs were common. The lifetime prevalence of DSM-5 AN was higher than previously reported for DSM-IV AN but comparable to prior estimates of ‘broad’ DSM-IV AN [
34] and expected given the removal of the amenorrhea criterion in DSM-5 [
34], and the older age of our sample. The lifetime prevalence of BN and BED were also in line with previous community studies [
35], although surprisingly, BED was less common during lifetime compared to AN and BN. This might be due to a higher percentage of highly educated women participating in Phase 1, and the ethnic composition of ALSPAC [
15]. EDs other than AN, BN, and BED, now subsumed under OSFED, were common in this sample (7.6%), in particular the residual unspecified category (other OSFED). This suggests that, despite efforts in DSM-5 to reduce the prevalence of the ‘unspecified’ category (a goal of the revisions to DSM-IV), as previously shown [
4,
6,
9], many individuals in the community experience EDs other than AN, BN, and BED. The relatively large subset of women presenting with ‘other OSFED’ (27.6% of all OSFED) is in line with our own [
4] and others’ research [
36].
EDs in the year prior to interview were more common than expected, no previous study – to our knowledge – has investigated the period prevalence of DSM-5 ED in a community sample in mid-life. OSFED was the most common ED, accounting for almost half of all prevalent ED cases and BED was the most common full-threshold disorder. These findings highlight, for the first time, that EDs are not confined to earlier decades of life and that both chronic and new onset disorders are apparent in this stage of life.
Although our data cover a wide time lag (last 40 years) and might therefore reflect past rather than current lack of identification of EDs and related healthcare provision in the UK, it is nevertheless surprising that, across their lifetime, very few women had sought or received treatment for EDs.
Our investigation of risk factors of lifetime EDs revealed important findings. Childhood sexual abuse, unhappiness, and low parental care were associated with binge and/or purge-type ED (AN-BP, full and sub-threshold BN and BED). The association between childhood sexual abuse and binge and/or purge-type ED is consistent with previous retrospective studies [
14,
37,
38], and extends this evidence to sub-threshold ED. In line with our recent meta-analysis [
11] and previous hypotheses that parenting risk factors and parental influences might act differently across the ED diagnostic spectrum [
14], parental overprotection and low maternal care were associated with binge and/or purge disorders, but not AN. We recently showed that retrospectively reported parental influences (including poor parenting and overprotection) predicted body dissatisfaction in women with BN and AN-BP but not AN-R [
39]. This association with binge/purge type disorders maybe mediated via negative affect, low self-esteem, or body dissatisfaction developmentally, as might be the case with sexual abuse. Further longitudinal studies are required to empirically test these pathways.
High interpersonal sensitivity was associated with all EDs. Interpersonal sensitivity has been described as sensitivity to other’s feedback and fear of social rejection [
26], and it is characterized by misinterpretation of interpersonal behaviors, interpersonal avoidance and discomfort in the presence of others due to a sense of inadequacy. Our finding confirms and strengthens existing cross-sectional evidence that social impairment and interpersonal difficulties are common across EDs [
11], and might contribute to their onset and maintenance [
11,
40].
We replicated associations identified in clinical studies between high IQ and AN [
41,
42], in a community setting (women with lifetime AN-BP had a total IQ on average 5 points higher than women with no EDs). Whether the higher IQ observed is secondary to higher levels of perfectionism, or indeed indexes specific cognitive strengths requires further study and elucidation.
This study is the first to investigate childhood risk factors for PD, a newly described ED. The only twin study of PD recently showed that non-shared environmental factors explained 56% of the variance for PD [
43]; however, the study could not disentangle the effect of non-shared environment versus genetic factors. Our findings suggest a role for childhood experiences and parenting as risk factors for PD. Similarly, this is the first study to investigate risk factors for atypical AN, with initial evidence of a risk factor profile more similar to binge/purge type ED than AN-R. This is the first study to show a similar pattern of risk for full threshold and sub-threshold BN and BED. These findings, together with evidence of similar outcomes between threshold and sub-threshold BN and BED [
4], confirm similarities between full and sub-threshold ED, in this case in relation to risk factors.
Few associations were identified between environmental risk variables and restrictive AN. This finding might reflect our hierarchical approach to lifetime diagnosis, in that to be included in this group, women had to have met criteria for AN-R only (and not other EDs). As such, our findings point to a smaller contribution of environmental risk to this phenotype [
34].
Strengths of the study include a large community sample of women, overcoming bias introduced by studying treatment-seeking individuals. The two-phase epidemiological design, one of the best approaches to estimate prevalence of disease [
44], and the survey analytical techniques allowed more accurate estimates to be obtained using our entire Phase I sample. We used a validated and reliable assessment for EDs and supplemented this with a longitudinal assessment of lifetime symptoms to obtain DSM-5 diagnoses. The availability of risk factor data independently collected 20 years prior to the current study allowed a less biased estimation of risk factors, although recall bias might explain some of our findings.
Limitations of the study include the nature of the ALSPAC cohort, i.e. women who were pregnant at a specific point in time in a defined geographic area. The sample is therefore likely to include women with ED who were able to become pregnant at least once and is therefore not representative of the general population. Nevertheless, the lowest ever self-reported BMI in this sample was 10.7, and the lowest measured BMI at mean age 48 years was 15.4, suggesting a range of ED severity within the sample. Participation in Phase 1 was selective; however, we were able to determine that more educated women and those with fewer children participated. Despite attrition between Phase 1 and 2, our analytical approach allows minimizing bias due to attrition. Moreover, risk factor analyses were controlled for socio-demographic factors associated with non-participation in Phase 1, therefore increasing generalizability of the findings. It is possible that women with higher levels of psychopathology were less represented in this study; however, levels of self-reported EDs at enrolment were comparable across participants and non-participants, therefore we are unlikely to have underestimated the prevalence of EDs. Small sample size in some diagnostic groups might account for false negatives. Similarly, chance might explain some of our positive findings. We could not directly investigate other psychiatric disorders and, therefore, the specificity of risk factors for ED versus other psychopathology needs elucidating further.
Acknowledgements
We are extremely grateful to all the families who took part in this study, the midwives for their help in recruiting them, and the whole ALSPAC team, which includes interviewers, computer and laboratory technicians, clerical workers, research scientists, volunteers, managers, receptionists and nurses. We are particularly grateful to all the women who participated and shared their stories with the research team. We would like to thank Dr Luigi Palla, for his statistical support. We would like to thank the reviewers for their helpful suggestions.