Effects of increased body mass index on employment status: a Mendelian randomisation study

Desmond D Campbell,Michael Green,Rona J Strawbridge,Joey Ward,Keira J A Johnston,Srinivasa Vittal Katikireddi,Laura D Howe,Frank Popham,Daniel J Smith,Marcus R Munafò,Sean Harrison,Neil Davies,Evangelia Demou

doi:10.1038/s41366-021-00846-x

Abstract

BackgroundThe obesity epidemic may have substantial implications for the global workforce, including causal effects on employment, but clear evidence is lacking. Obesity may prevent people from being in paid work through poor health or through social discrimination. We studied genetic variants robustly associated with body mass index (BMI) to investigate its causal effects on employment.Dataset/methodsWhite UK ethnicity participants of working age (men 40–64 years, women 40–59 years), with suitable genetic data were selected in the UK Biobank study (N = 230,791). Employment status was categorised in two ways: first, contrasting being in paid employment with any other status; and second, contrasting being in paid employment with sickness/disability, unemployment, early retirement and caring for home/family. Socioeconomic indicators also investigated were hours worked, household income, educational attainment and Townsend deprivation index (TDI). We conducted observational and two-sample Mendelian randomisation (MR) analyses to investigate the effect of increased BMI on employment-related outcomes.ResultsRegressions showed BMI associated with all the employment-related outcomes investigated. MR analyses provided evidence for higher BMI causing increased risk of sickness/disability (OR 1.08, 95% CI 1.04, 1.11, per 1 Kg/m2 BMI increase) and decreased caring for home/family (OR 0.96, 95% CI 0.93, 0.99), higher TDI (Beta 0.038, 95% CI 0.018, 0.059), and lower household income (OR 0.98, 95% CI 0.96, 0.99). In contrast, MR provided evidence for no causal effect of BMI on unemployment, early retirement, non-employment, hours worked or educational attainment. There was little evidence for causal effects differing by sex or age. Robustness tests yielded consistent results.DiscussionBMI appears to exert a causal effect on employment status, largely by affecting an individual’s health rather than through increased unemployment arising from social discrimination. The obesity epidemic may be contributing to increased worklessness and therefore could impose a substantial societal burden.

Highlights

We investigated the impact of body mass index (BMI) on indicators related to socioeconomic conditions— namely, household income, educational attainment and area-based deprivation
We identified genetic instruments for BMI based on a set of single nucleotide polymorphisms (SNPs) which were robustly associated in a genome wide association study (GWAS) [15]
We investigated the causal effect of BMI on employmentrelated outcomes in the UK Biobank study by utilising a set of genetic variants robustly associated with increased BMI

Summary

Introduction

4 million deaths globally, nearly 40% of which occurred in non-obese people [1]. This obesity epidemic has been underpinned by a mean shift in the population distribution of body mass index (BMI) rather than just an increase in the high BMI tail of the distribution. While there has been a considerable focus on the associated healthcare costs arising from higher weight [2], the broader adverse consequences to society are less understood [3] These impacts may be substantial, with the broader economic costs potentially dwarfing the direct healthcare costs. We studied genetic variants robustly associated with body mass index (BMI) to investigate its causal effects on employment. We conducted observational and two-sample Mendelian randomisation (MR) analyses to investigate the effect of increased BMI on employment-related outcomes

Methods

Results

Conclusion