Background: Disparities in body mass index (BMI) between persons with different educational levels in Western countries are well documented, but the background of these education-associated disparities remains poorly understood.
Objective: The objective was to examine the influence of environmental and genetic factors on education-associated disparities in self-reported BMI and weight change.
Design: Longitudinal postal surveys were performed in 1975, 1981, and 1990. The data were analyzed by using multivariate genetic models for twin data. The data derived from the Finnish Twin Cohort included 2482 monozygotic and 5113 dizygotic same-sex male and female twin pairs born between 1915 and 1957.
Results: Education-associated differences in BMI and in weight change were clear in 1975 and 1981, respectively, whereas no differences were seen in weight change between 1981 and 1990 when age and baseline BMI were adjusted for. The trait correlation between baseline BMI and educational attainment (-0.15 in men and women) was mainly due to correlations between additive genetic factors that contributed to BMI and education in men (-0.20; 95% CI: -0.25, -0.14) and women (-0.32; 95% CI: -0.40, -0.25) when adjusted for age. Among women, a weaker positive correlation was found for the unshared environmental effects contributing to the 2 traits (0.06; 95% CI: 0.02, 0.12). The same factors that affected the association between education and BMI in 1975 largely explained the association between education and weight change in 1981.
Conclusion: The results suggest the possibility that common genetic factors affect educational attainment and body weight, which contribute to education-associated disparities in BMI in adulthood.