Abstract
BackgroundWe assessed whether body mass index (BMI) affects social and socio-economic outcomes.MethodsWe used Mendelian randomization (MR), non-linear MR and non-genetic and MR within-sibling analyses, to estimate relationships of BMI with six socio-economic and four social outcomes in 378 244 people of European ancestry in UK Biobank.ResultsIn MR of minimally related individuals, higher BMI was related to higher deprivation, lower income, fewer years of education, lower odds of degree-level education and skilled employment. Non-linear MR suggested both low (bottom decile, <22 kg/m2) and high (top seven deciles, >24.6 kg/m2) BMI, increased deprivation and reduced income. Non-genetic within-sibling analysis supported an effect of BMI on socio-economic position (SEP); precision in within-sibling MR was too low to draw inference about effects of BMI on SEP. There was some evidence of pleiotropy, with MR Egger suggesting limited effects of BMI on deprivation, although precision of these estimates is also low. Non-linear MR suggested that low BMI (bottom three deciles, <23.5 kg/m2) reduces the odds of cohabiting with a partner or spouse in men, whereas high BMI (top two deciles, >30.7 kg/m2) reduces the odds of cohabitation in women. Both non-genetic and MR within-sibling analyses supported this sex-specific effect of BMI on cohabitation. In men only, higher BMI was related to lower participation in leisure and social activities. There was little evidence that BMI affects visits from friends and family or having someone to confide in.ConclusionsBMI may affect social and socio-economic outcomes, with both high and low BMI being detrimental for SEP, although larger within-family MR studies may help to test the robustness of MR results in unrelated individuals. Triangulation of evidence across MR and within-family analyses supports evidence of a sex-specific effect of BMI on cohabitation.
Highlights
Using Mendelian randomization (MR), a technique that uses genetic data to overcome confounding and reverse causality, we found evidence of sex-specific effects of body mass index (BMI) on the likelihood of being in a cohabiting relationship with a partner or spouse: in men, lower BMI was associated with being less likely to live with a partner or spouse, whereas in women, higher BMI was associated with being less likely to live with a partner or spouse
Using triangulation across a range of methods, we have explored the social and socio-economic consequences of BMI
MR analysis in $350 000 unrelated participants suggested that both low BMI (24.6 kg/m2) may lead to lower socio-economic position (SEP) in both men and women, that high BMI is related to lower chance of being in a cohabitating relationship for women but lower BMI is related to lower chance of being in a cohabiting relationship for men, and that higher BMI can lead to men being less likely to participate in leisure activities
Summary
Lower socio-economic position (SEP) is associated with higher body mass index (BMI) and greater risk of obesity in high-income countries.[1,2,3,4] People with higher BMI are more likely to experience weight-related stigma or discrimination, lower self-esteem, and physical and mental ill-health,[5,6,7,8,9,10,11,12,13] all of which could potentially affect social, educational and employment outcomes, meaning that the relationships between social factors and BMI could be bidirectional. Non-linear MR suggested both low (bottom decile, 24.6 kg/m2) BMI, increased deprivation and reduced income. Non-linear MR suggested that low BMI (bottom three deciles, 30.7 kg/m2) reduces the odds of cohabitation in women Both non-genetic and MR within-sibling analyses supported this sex-specific effect of BMI on cohabitation.
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