Socio-economic differences in body mass index: the contribution of genetic factors

Background Higher mean body mass index (BMI) among lower socioeconomic position (SEP) groups is well established in Western societies, but the influence of genetic factors on these differences is not well characterized. Methods We analyzed these associations using Finnish health surveys conducted between 1992 and 2017 ( N = 33 523; 53% women) with information on measured weight and height, polygenic risk scores of BMI (PGS-BMI) and linked data from administrative registers to measure educational attainment, occupation-based social class and personal income. Results In linear regressions, largest adjusted BMI differences were found between basic and tertiary educated men (1.4 kg/m 2 , 95% confidence interval [CI] 1.2; 1.6) and women (2.5 kg/m 2 , 95% CI 2.3; 2.8), and inverse BMI gradients were also found for social class and income. These SEP differences arose partly because mean PGS-BMI was higher and partly because PGS-BMI predicted BMI more strongly in lower SEP groups. The inverse SEP gradients of BMI were steeper in women than in men, but sex differences were not found in the genetic contributions to these differences. Conclusions Better understanding of the interplay between genes and environment provides insight into the mechanisms explaining SEP differences in BMI.