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

8 Citations (Scopus)
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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
Pages (from-to)1790-1801
Number of pages12
JournalInternational Journal of Obesity
Volume45
Issue number8
Early online date22 Jun 2021
DOIs
Publication statusPublished - 1 Aug 2021

Bibliographical note

Funding Information:
Programme Studentship at the Universities of Glasgow and Edinburgh. DS acknowledges the support of the Brain and Behaviour Research Foundation (Independent Investigator Award 1930) and a Lister Prize Fellowship (173096). RS is supported by a UKRI Innovation-HDR-UK Fellowship (MR/S003061/1). DC is supported by a Health Foundation, Social and economic value of health award (756273). MG acknowledges funding from the Medical Research Council (MC_UU_12017/13) and Chief Scientist Office Grant (SPHSU13), as well as under the Health Foundation grant (756273). SVK acknowledges funding from a NRS Senior Clinical Fellowship (SCAF/15/02), the Medical Research Council (MC_UU_00022/2), the Scottish Government Chief Scientist Office (SPHSU17) and the Health Foundation (756273). NMD is supported by a Norwegian Research Council Grant number 295989.

Funding Information:
Acknowledgements This research was supported by The Health Foundation Social and Economic Value of Health programme (award 756273), Medical Research Council grant (MC_UU_00022/2) and Chief Scientist Office Grant (SPHSU17). This research has been conducted using the UK Biobank Resource under Application Number 17333. We thank all participants, staff and funders of the UK Biobank study, and the NHS staff who collected data provided by patients as part of their care and support. ED acknowledges funding by MRC Strategic Award (MC_PC_13027). JW is supported by a Lister Prize Fellowship (173096). KJ is supported by an MRC Doctoral Training

Publisher Copyright:
© 2021, The Author(s).

Keywords

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

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