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

Abstract

Frontier populations provide exceptional opportunities to test the hypothesis of a trade-off between fertility and longevity. In such populations, mechanisms favoring reproduction usually find fertile ground, and if these mechanisms reduce longevity, demographers should observe higher postreproductive mortality among highly fertile women. We test this hypothesis using complete female reproductive histories from three large demographic databases: the Registre de la population du Québec ancien (Université de Montréal), which covers the first centuries of settlement in Quebec; the BALSAC database (Université du Québec à Chicoutimi), including comprehensive records for the Saguenay-Lac-St-Jean (SLSJ) in Quebec in the nineteenth and twentieth centuries; and the Utah Population Database (University of Utah), including all individuals who experienced a vital event on the Mormon Trail and their descendants. Together, the three samples allow for comparisons over time and space, and represent one of the largest set of natural fertility cohorts used to simultaneously assess reproduction and longevity. Using survival analyses, we found a negative influence of parity and a positive influence of age at last child on postreproductive survival in the three populations, as well as a significant interaction between these two variables. The effect sizes of all these parameters were remarkably similar in the three samples. However, we found little evidence that early fertility affects postreproductive survival. The use of Heckman’s procedure assessing the impact of mortality selection during reproductive ages did not appreciably alter these results. We conclude our empirical investigation by discussing the advantages of comparative approaches. Am. J. Hum. Biol. 21:533–540, 2009.

Childhood socioeconomic status, adult socioeconomic status, and old-age health trajectories

“…Of course, as studies traverse backward in time they are bound by available data, a common challenge in historical demography and anthropology but from which considerable insights have been derived (Knodel and Van de Walle 1979). There are also other contemporary and historic samples such as the BALSAC database from Quebec that have dominant religions and high fertility, and their samples have led to important findings (Gagnon et al 2009). Plus, the uniqueness of the current sample should not be overstated.…”

How grandmother effects plus individual variation in frailty shape fertility and mortality: Guidance from human–chimpanzee comparisons

“…Life history variation among individuals of the same population often seems to go in the opposite direction as well. Women with higher fertility rates and later ages at last birth also have higher subsequent survival rates (23)(24)(25)(67)(68)(69). Such apparent absence of the expected tradeoffs within populations is a regular finding in field studies in animal behavior (70)(71)(72).…”

“…I focus on two apparent inconsistencies between theoretical expectations and empirical observations. First, theory predicts that current reproductive output should subtract from effort invested in maintenance for survival and reproduction in the future, yet individuals with higher fertility rates tend to continue bearing offspring to older ages; and in humans, women with later last births then survive longer afterward (22)(23)(24)(25). Second, theory predicts that lower adult mortality should slow rates of senescence, yet when populations of the same species are compared, the groups with lower mortality have steeper increases in death risk with advancing age (26,27).…”

The mid-twentieth century Baby Boom and the changing educational gradient in Belgian cohort fertility

“…This is a stylized fact that research findings have not unequivocally supported. In particular, empirical research in historical populations that practice only archaic forms of fertility control has not generally confirmed higher mortality among high parity women (Westendorp and Kirkwood 1998;Dribe 2004;Le Bourg 2007;Gagnon et al 2009). In more recent populations practicing more modern contraception, like the Belgian population studied here, the results have been clearer, although longevity in the strict sense of the word can often not yet be studied for recent cohorts since they are too recent to be living long enough.…”