Childhood body mass index and the subsequent risk of anorexia nervosa and bulimia nervosa among women: A large Danish population‐based study

Abstract

ObjectiveEvidence linking childhood body mass index (BMI) with subsequent eating disorders is equivocal. Potential explanations include different study populations and size, and that anorexia nervosa (AN) and bulimia nervosa (BN) should be studied separately. We examined whether birthweight and childhood BMI were associated with subsequent risk of AN and BN in girls.MethodWe included 68,793 girls from the Copenhagen School Health Records Register born between 1960 and 1996 with information on birthweight and measured weights and heights obtained from school health examinations at ages 6–15 years. Diagnoses of AN and BN were retrieved from Danish nationwide patient registers. We used Cox proportional hazards regression to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).ResultsWe identified 355 cases of AN (median age: 19.0) and 273 cases of BN (median age: 21.8). Higher childhood BMI was linearly associated with decreasing risk of AN and increasing risk of BN at all childhood ages. At age 6, the HR for AN was 0.85 (95% CI: 0.74–0.97) per BMI z‐score and the HR for BN was 1.78 (95% CI: 1.50–2.11) per BMI z‐score. Birthweight >3.75 kg was associated with increased risk of BN compared to a birthweight of 3.26–3.75 kg.ConclusionHigher BMI in girls at ages 6–15 years was associated with decreasing risk of AN and increasing risk of BN. Premorbid BMI could be relevant for the etiology of AN and BN, and in identifying high risk individuals.Public significanceEating disorders are associated with elevated mortality, especially AN. Using a cohort of Copenhagen school children, we linked information on BMI at ages 6–15 years for 68,793 girls with nationwide patient registers. Low childhood BMI was associated with increased risk of AN, whereas high childhood BMI was associated with increased risk of BN. These findings may assist clinicians in identifying individuals at high‐risk of these diseases.

Premorbid body weight predicts weight loss in both anorexia nervosa and atypical anorexia nervosa: Further support for a single underlying disorder

“…Our findings suggest that the preponderance of premorbid overweight/obesity and higher premorbid BMI in patients with atypical AN (Walsh et al, 2023) is related to the diagnostic weight cutoff. Conversely, the epidemiological associations (Leth-Moller et al, 2023;Stice et al, 2017Stice et al, , 2022Yilmaz et al, 2019) and genetic correlations (Watson et al, 2019) between a low premorbid BMI and AN may partially, if not completely, result from the diagnostic requirement of a 'significantly low body weight' in AN (Leth-Moller et al, 2023). In the second part of our study, exploratory analyses compared AN and atypical AN in terms of weight loss, anthropometric variables, age, and illness duration.…”

“…Compared to patients with atypical AN, there is a lower prevalence of premorbid overweight/obesity and lower maximal BMI in patients with AN (Walsh et al, 2023). Further, epidemiological studies have demonstrated associations between low childhood BMI and increased AN risk (Leth-Moller et al, 2023;Stice et al, 2017Stice et al, , 2022Yilmaz et al, 2019) and genome wide association studies (Duncan et al, 2017;Watson et al, 2019) have identified genetic correlations between AN, low BMI, and associated traits. For example, in the Avon Longitudinal Study of Parents and Children (Abdulkadir et al, 2022), female participants with a high polygenic score for AN and a low polygenic score for BMI constituted a high-risk group for AN.…”

Differentiating anorexia nervosa and atypical anorexia nervosa with absolute weight cut‐offs results in a skewed distribution for premorbid weight among youth

“…Prior genetic and epidemiological studies document an association between 'underweight' and AN, insofar as individuals with unique metabolic and anthropomorphic phenotypes corresponding with 'underweight' (e.g., low BMI, percent body fat, and waist circumference) (Watson et al, 2019) and individuals with lower childhood BMIs (Leth-Moller et al, 2023;Stice et al, 2017Stice et al, , 2022Yilmaz et al, 2019) are at heightened risk for developing AN.…”