Ambient Temperature During Gestation and Cold-related Adult Mortality in a Swedish Cohort, 1915-2002

ABSTRACT: 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 month of birth. This research as well as literature documenting developmental plasticity and culling in utero implies the hypothesis that ambient temperature during gestation may influence cold-related adult mortality. We use data on over 13,500 Swedes to test whether subjects whose mothers experienced unusually benign ambient temperatures during their gestation exhibit an elevated risk of cold-related mortality in adulthood. We linked instrument-based, daily temperatures to subjects beginning at their estimated date of conception and ending at death or the end of follow-up. We specified a counting process Cox proportional hazards model to analyze the two leading causes of cold-related death in adulthood: ischaemic heart disease (IHD) and stroke. We find an increased risk of IHD death during cold spells among adults whose mothers experienced relatively warm ambient temperature during pregnancy. We, however, observe no relation for stroke mortality. The IHD findings indicate that ambient temperature during gestation¿independent of birth month¿modifies the relation between cold and adult mortality.