Genetic and environmental influences on educational disparities in adult weight change: an individual-based pooled analysis of 11 twin cohorts

Abstract

INTRODUCTION: Educational attainment (EA) is negatively associated with body mass index (BMI), but less is known about the association between EA and adult BMI change. We analysed the role of genetic and environmental factors in the associations between EA and BMI trajectory components over adulthood. DATA AND METHODS: Pooled data from 59,490 twins aged 31-99 years (49% women) across 11 cohorts with EA and repeated measures of BMI were used. BMI trajectory components (baseline BMI and BMI change per decade) were estimated using linear mixed-effects (LME) and delta slope methods. EA was derived by regressing years of education on birth year and cohort. Associations between EA and BMI trajectories were evaluated with LME models in both cohort-specific and pooled data. Genetic and environmental contributions were evaluated using structural equation modelling. RESULTS: EA was more strongly negatively associated with baseline BMI and BMI change (mean of 1.31 and 1.32 kg/m(2) per decade in men and women, respectively) in women (? = -0.14 kg/m², 95% CI: -0.15 to -0.12; ? = -0.02 kg/m²/decade, 95% CI: -0.03 to -0.01, respectively) than in men (? = -0.07, 95% CI: -0.08 to -0.06; ? = -0.01, 95% CI: -0.02 to -0.001, respectively). The associations between baseline BMI and EA were explained by genetic factors in men (r(A) = -0.10) and by both genetic (r(A) = -0.17) and unique environmental factors (r(E) = -0.07) in women. For BMI change, the associations with EA were explained by genetic factors (r(A) = -0.04 in men; -0.06 in women). CONCLUSION: Individuals with higher EA tend to have lower baseline BMI and slower BMI increases across adulthood. These associations are primarily genetically mediated.