Social and economic consequences of health status Causal inference methods and longitudinal, intergenerational data

This project led by the University of Bristol explored the impact of childhood obesity on education outcomes. It sought to improve understanding of the causal health impact on social and economic outcomes. The research included:

• analysis of data from studies including UK Biobank, the Avon Longitudinal Study of Parents and Children, and the Norwegian Mother and Child cohort study
• analysis of results from in-depth interviews
• use of Mendelian randomisation – which uses genetic variants as variables to avoid bias from confounding and reverse causality – to find out whether the associations between health and social and economic outcomes are causal.  

Key findings

• High body mass index (BMI) has a causal effect on fewer years of education, higher deprivation, lower income and lower odds of being in skilled employment, but family-level effects might be driving these associations.
• Part of the effect of higher BMI on lower education seems to be driven by higher levels of absence from school.
• Smoking and alcohol also appear to detrimentally affect a wide range of economic outcomes.
• Higher genetic liability to attention deficit hyperactivity disorder (ADHD) is associated with lower educational attainment, and this is not explained by school absences or cognitive ability.

In terms of quantifying potential returns, it was found that the effect of BMI on hospital costs is likely to be higher than previously estimated: a unit increase in BMI decreased quality-adjusted life years (QALYs) by 0.65% of a QALY per year when considering a broad range of health conditions. It was also found that interventions to reduce BMI are cost-effective. These findings support the case for an obesity strategy that involves interventions at the population level, and forward-planning for obesity reduction.

The project team has published their research findings widely (see links below), including methodological guidance for the within-family Mendelian randomisation approach.

Contact information

Questions? Please contact Laura Howe, Professor of Epidemiology and Medical Statistics, University of Bristol.

Learn more

For more information about this project, please see the resources below:

Mendelian Randomization analysis of the causal effect of adiposity on hospital costs

Effects of body mass index on relationship status, social contact and socio-economic position: Mendelian randomization and within-sibling study in UK Biobank

The causal effects of health conditions and risk factors on social and socioeconomic outcomes: Mendelian randomization in UK Biobank

Common health conditions in childhood and adolescence, school absence, and educational attainment: Mendelian randomization study

Avoiding dynastic, assortative mating, and population stratification biases in Mendelian randomization through within-family analyses

Is genetic liability to ADHD and ASD causally linked to educational attainment?

The role of school enjoyment in the association between externalising and depressive symptoms and academic attainment: findings from a UK prospective cohort study

Robust causal inference for long-term policy decisions: cost effectiveness of interventions for obesity using Mendelian randomization

Links between obesity, weight stigma and learning in adolescence: a qualitative study