Ambient temperature in utero and cold-related adult mortality in a Swedish cohort, 1915 to 2002

For all climatic regions, mortality due to cold exceeds mortality due to heat. A separate line of research indicates that lifespan after age 50 depends on season of birth. This and other literature implies that ambient temperature in utero may influence cold-related mortality later in life. We use data on over 13,500 Swedes (from 1915 to 2002) to test whether cold-related mortality in adulthood varies positively with exposure to unusually benign ambient temperature in utero. We specify a counting process Cox proportional hazards model to analyze the two leading causes of cold-related death: ischemic heart disease and stroke. Results indicate an increased risk of ischemic heart disease mortality during cold spells among persons exposed to relatively warm gestations. We, however, observe no relation for stroke mortality. The ischemic heart disease findings provide the first evidence that temperature during gestation—independent of month of birth—affects cold-related mortality later in life.