A genetic sum score of risk alleles associated with body mass index interacts with socioeconomic position in the Heinz Nixdorf Recall Study

Abstract

Body mass index (BMI) is influenced by genetic, behavioral and environmental factors, while interactions between genetic and socioeconomic factors have been suggested. Aim of the study was to investigate whether socioeconomic position (SEP) interacts with a BMI-related genetic sum score (GRSBMI) to affect BMI in a population-based cohort. SEP-related health behaviors and a GRS associated with educational attainment (GRSEdu) were included in the analysis to explore potential interactions underlying the GRSBMIxSEP effect. Baseline information on SEP indicators (education, income), BMI, smoking, physical activity, alcohol consumption and genetic risk factors were available for 4,493 participants of the Heinz Nixdorf Recall Study. Interaction analysis was based on linear regression as well as on stratified analyses. In SEP-stratified analyses, the highest genetic effects were observed in the lowest educational group with a 0.24 kg/m2 higher BMI (95%CI: 0.16; 0.31) and in the lowest income quartile with a 0.14 kg/m2 higher BMI (95%CI: 0.09; 0.18) per additional risk allele. Indication for a GRSBMIxSEP interaction was observed for education (ßGRSbmixeducation = -0.02 [95%CI:-0.03; -0.01]) and income (ßGRSbmixincome = -0.05 [95%CI: -0.08; -0.02]). When adjusting for interactions with the GRSEdu and SEP-related health behaviors, effect size estimates of the GRSBMIxSEP interaction remained virtually unchanged. Results gave indication for an interaction of BMI-related genetic risk factors with SEP indicators, showing substantially stronger genetic effects in low SEP groups. This supports the hypothesis that expression of genetic risks is higher in socioeconomically disadvantaged environments. No indication was observed that the GRSBMIxSEP interaction was affected by other SEP-related factors included in the analysis.

Fig 1. Sex- and age-adjusted effects and corresponding 95% confidence interval (95% CI) of the genetic effect on body mass index (BMI), stratified by education groups (years) and income quartiles in linear regression models.