The Effect of BMI and Type 2 Diabetes on Socioeconomic Status: A Two-Sample Multivariable Mendelian Randomization Study

CONCLUSIONS

In this study, we estimated the independent effects of BMI and T2D on household income and regional deprivation using a novel multivariable MR technique (8). Our results indicate negative effects of BMI but no effect of diabetes.

​ These findings strengthen the evidence of the deleterious (有毒的，有害的) role of BMI on income and regional deprivation reported in previous observational and one-sample MR studies (1,4–6). The potential underlying mechanisms include a lower ability to work, higher absenteeism, higher probability of musculoskeletal (肌肉骨骼) injuries, and higher discrimination (歧视), which may lead to poorer career prospects, decreasing labor market participation, and lower income (1). A lower income could in turn affect living standards, leading individuals to self-select into more deprived areas with more affordable housing and food options.

​ Similar to a previous one-sample MR study (5), our results did not show any significant effect of T2D on household income or regional deprivation. In contrast, other studies that did not use a multivariate two-sample MR approach showed a negative effect of diabetes on socioeconomic outcomes (2,3). This result should be object of further studies, aiming at establishing whether this null effect can be replicated or whether it is mainly due to methodological shortcomings in our study.

​ In fact, this study has some methodological limitations. First, despite the fact that genetic characteristics are independent of possible confounders, high BMI or diabetes genetic risk of parents might be an unmeasured confounder, causing a “dynastic bias” (15). Second, although the relevance assumption of our IVs is satisfied, the explanatory power (解释力) of the set of SNPs used in the analysis for both the exposures and the outcomes is limited (10,11). Finally, because the UK Biobank population is a selected one (13), our results might suffer from selection bias.

​ In conclusion, the current study provides evidence of a negative causal effect of higher BMI on income and regional deprivation, controlling for diabetes (并控制了糖尿病这个变量). In contrast, T2D does not have an effect on these two socioeconomic outcomes. Further studies should investigate this result, using new generations of GWAS with a higher explanatory power and including a more representative population. Furthermore, applied research may help to improve the understanding for the underlying mechanisms and to create targeted strategies to break the negative connection between BMI and socioeconomic outcomes.

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