Women giving birth at advanced reproductive ages in natural fertility conditions have been shown to have superior postmenopausal longevity. It is unknown whether improved survival is more likely among relatives of late-fertile women. This study compares survival past age 50 of men with and without a late-fertile sister in two populations: Utahns born in 1800-1869 identified from the Utah Population Database and Québec residents born in 1670-1750 identified from the Programme de recherche en démographie historique. Male survival was greater for those with, rather than without, a sister reproducing after age 45, particularly among men with at least three sisters (Utah rate ratio [RR] = .801, 95% CI = 0.687-0.940; Quebec RR = .786, 95% CI = 0.664-0.931). Survival of wives was unaffected by whether their husbands had a late-fertile sister, suggesting a weak influence of unmeasured socioenvironmental factors. These results support the hypothesis that late female fertility and slow somatic aging may be promoted by the same genetic variants.
Fertility patterns may be useful markers for rates of biological aging. Based on evolutionary and socio-demographic approaches to historical data from the population of Québec (taken from the Registre de population du Québec ancien at the University of Montreal), we examine the effects of reproduction on longevity. Using Cox hazard models on about 2,000 couples married in the colony before 1740, we show that women bearing their last child late in life had longer post-reproductive lives, suggesting that late menopause is associated with an overall slower rate of aging. Increased parity had an opposite, detrimental effect on women's post-reproductive survival. On the other hand, husband's longevity was less sensitive to parity and reproductive history. For husbands increased effective family size (EFS; the number of children who survived up to age 18) in a "compressed" reproductive time-span meant higher chances for survival past age 60.Children may serve as strong economical assets on farmstead during colonization, which would mostly benefit fathers. In a collaborative effort to unveil post-reproductive aging patterns in historical populations, the results are compared to previous analyses conducted on the Utah population database and evolutionary and socio-demographic theories addressed in light of the results.3
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