Early-life disease exposure and its heterogeneous effects on mortality across life: Sweden 1905-2016

Exposure to infectious diseases in early life has been linked to increased mortality risk in later life in high-disease settings, such as 18th-19th century Europe. Less is known about the long-term effects of early-life disease exposure in milder disease environments. The aim of this study is to estimate heterogeneous effects from exposure to disease in infancy on later-life mortality in 20th century Sweden, by socioeconomic status at birth and sex. We use historical population data for Southern Sweden and study 11,515 individuals born 1905-1929 between ages 1-85. We measure exposure to disease using the local post-early neonatal mortality rate in the first 12 months after birth and apply flexible parametric survival models. We find a negative effect on life expectancy (scarring) between ages 1-85 following high disease exposure in infancy for females, particularly those born to unskilled workers. For males, there is no negative effect on later-life survival, likely because of stronger mortality selection in infancy outweighing scarring. Thus, even as the incidence of infectious diseases declined at the start of the 20th century, exposure to disease in early life generated long-lasting negative, but heterogeneous, health effects in the population.