Postreproductive Longevity in a Natural Fertility Population

Abstract

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

Is there a trade‐off between fertility and longevity? A comparative study of women from three large historical databases accounting for mortality selection

“…This replicated result is consistent with the hypothesis of a slower rate of aging among women with late child bearing. We find additional support in the fact that brothers of women with a late childbearing also tend to survive longer (Smith et al, 2008).…”

“…Hence, there may be relatively little selection on the timing of first reproduction within a fairly large range of ages (Helle et al, 2005). It is possible, however, that a genuine beneficial effect of delayed first birth was blurred in the two Quebec samples because delayed first marriage--and delayed first pregnancy--may be the result of poor health (Gagnon et al, 2008).…”

“…About a year later, Gavrilov and Gavrilova (1999) retorted that Wesdendorp and Kirwood's account failed to adjust for the obvious confounder of age at marriage (''the most important explanatory variable for both age at first child and family size'') and that the data used were inappropriate for such a study (incomplete genealogies with many underreported records). This critique was echoed in Le Bourg's review (2001) and in a number of more recent contributions (e.g., Gagnon et al, 2008).…”

“…As an illustration of the divergence of findings, three studies found a positive relationship between total parity and postreproductive survival (Mü ller et al, 2002;Sear, 2007;Voland and Engel, 1986), three studies found the opposite (Doblhammer and Oeppen, 2003;Gagnon et al, 2008;Smith et al, 2002), and four other studies showed no significant relationship (Bideau, 1986;Helle et al, 2002;Knodel, 1988;Le Bourg et al, 1993). Ironically, among these references, the same data on Old Quebec were used to support each of the three claims!…”

“…), population characteristics (e.g., with or without fertility control), and sample selection criteria (Grundy and Tomassini, 2005;Hurt et al, 2006). Following work initiated by Smith et al (2002), and pursued in Gagnon et al (2008), the present comparative study attempts to alleviate these problems using the same sample selection criteria and performing the same statistical methods in three historical populations: The Registre de la population du Québec ancien at the Université de Montréal, the BALSAC database at the Université du Québec à Chicoutimi, and the Utah Population Database at the University of Utah. Together, the three databases allow for an examination at different time points (Historical Quebec versus the more recent Quebec and Utah) and at different geographic locations (Quebec versus Utah).…”