  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.
