Do the Differences in Life Span by Month of Birth Persist among Cohorts Born Today? Evidence from the Minnesota Twin Family Study

Gabriele Doblhammer, Max Planck Institute for Demographic Research
Kaare Christensen, University of Southern Denmark

Low birthweight and fast catch-up growth in the first months of life causes higher susceptibility to cardiovascular disease later in life. Malnutrition in-utero and/or exposure to infectious disease probably are the causal mechanisms. Life span after age 50 depends on the month of birth and seasonal differences in nutrition and the incidence of infectious disease are the most likely causal factors. Since nutrition and the incidence of infectious disease vary seasonally one would expect a seasonal pattern by month of birth in birthweight, current weight, current height and current systolic blood pressure. This hypothesis is tested on the basis of the Minnesota twin family study. The month-of-birth patterns are compared with the differences in life span by month of birth for decedents aged 50+ who were born in Minnesota. The results for male twins suggest that in contemporary cohorts differences in life span by month of birth do persist.