Multigenerational effects of age at reproduction on longevity. Does grandparental age matter?

Marianne Caron, Université de Montréal
Valérie Jarry, Université de Montréal
Alain Gagnon, Université de Montréal

Biological and environmental events occurring in utero and during early life have been shown to have important effects on health and mortality throughout the life course. The literature also provides increasing empirical support for the idea that life-history experiences of parents, such as parental age, can greatly shape their children's future health and longevity outcomes. So far, most of the research investigating the link between parental age at reproduction and longevity in the offspring have focus almost exclusively on first-generation effects. Much fewer studies have investigated whether the effects of age at reproduction could extend to the third generation. It may however be important to acknowledge the interplay between grandparental and parental influences when exploring the transmission of health and longevity. In this paper, our main interest lies in the multigenerational effects of age at reproduction on the offspring’s longevity. Using data from extended ascending genealogies in the 17th and 18th centuries Quebec and event-history modeling methods, we test whether grandparental age at reproduction has consequences for the survival after age 50 of their grandchildren and whether such effects can be mediated by the parental age at the time of childbirth. We further examine if these potential influences may be mediated of modified by other early life and in utero characteristics such as parental and grandparental season of birth. In fact, parental and grandparental birth season may well have long-term consequences on their children and grandchildren's mortality outcomes via maternal and paternal epigenetic inheritance. Last, we are also interested in knowing how the gender composition would affect the results. These findings could have implications for understanding the biological and environmental basis of longevity but also for public health giving the demographic trend toward increasing parental age at conception in many countries.