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

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

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

Abstract

Background
The 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/Methods
White 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. Socio economic 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.

Results
Regressions 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.

Discussion
BMI 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.
Original languageEnglish
JournalInternational Journal of Obesity
Publication statusAccepted/In press - 27 Apr 2021

Keywords

  • obesity
  • body mass index
  • employment
  • work
  • unemployment
  • Mendelian randomisation
  • instrumental variables

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