Beyond Barker: Infant Mortality at Birth and Ischaemic Heart Disease in Older Age

TL;DR

This study extends Barker's findings by showing that early life conditions influence older age heart disease risk, especially for genetically predisposed individuals, highlighting the importance of environment in health outcomes.

Contribution

It demonstrates the robustness of early life effects on heart disease to geographic but not family fixed effects and reveals heterogeneity based on genetic risk.

Findings

Early life environment impacts older age heart disease risk.

Genetic predisposition effects are mitigated in low infant mortality areas.

Heterogeneity in effects is robust to within-area and within-family analyses.

Abstract

Adverse conditions in early life can have consequential impacts on individuals' health in older age. In one of the first papers on this topic, Barker and Osmond 1986 show a strong positive relationship between infant mortality rates in the 1920s and ischaemic heart disease in the 1970s. We go 'beyond Barker', first by showing that this relationship is robust to the inclusion of local geographic area fixed effects, but not family fixed effects. Second, we explore whether the average effects conceal underlying heterogeneity: we examine if the infant mortality effect offsets or reinforces one's genetic predisposition for heart disease. We find considerable heterogeneity that is robust to within-area as well as within-family analyses. Our findings show that the effects of one's early life environments mainly affect individuals with the highest genetic risk for developing heart disease. Put differently, in areas with the lowest infant mortality rates, the effect of one's genetic predisposition effectively vanishes. These findings suggest that advantageous environments can cushion one's genetic risk of developing heart disease.