Male lifespan following exposure to benign ambient temperature in utero and cold temperature in childhood

Ralph Catalano, University of California, Berkeley
Tim-Allen Bruckner, University of California, Irvine
Kirk Smith, University of California, Berkeley
Katherine Saxton, University of California, Berkeley

Environmental insults in utero reportedly cull frail male more than female fetuses, leaving behind a smaller but hardier cohort relative to males born in benign environments. This circumstance implies the hypothesis that a larger fraction of frail males will survive to birth if unexposed to ambient stressors, but will appear more susceptible later in life when confronted with environmental insults. We test this hypothesis in historical Sweden and use ambient temperature to gauge environmental stress. Time-series results find that male cohorts born under relatively salutary (i.e., warm) ambient temperatures exhibit lower than expected lifespan when exposed to cold temperatures in childhood. Findings support the notion of survival of frail male fetuses in benign conditions that, under adverse circumstances, would have been culled in utero. Survival to birth under favorable conditions, however, may reduce subsequent male lifespan, owing to increased sensitivity and exposure to cold temperatures in early childhood.