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Costs and Gains to Postponement: How Changes in the Age of Parenthood Influence the Health and Well-being of Children, the Parents, and Populations

Final Report Summary - COSTPOST (Costs and Gains to Postponement: How Changes in the Age of Parenthood Influence the Health and Well-being of Children, the Parents, and Populations)

The COSTPOST project is the first extensive set of analyses of the consequences of one of the most dramatic demographic changes of the 20th and early 21st century, the postponement of parenthood. Advanced maternal and paternal ages are associated with a range of negative outcomes for the offspring, and have been estimated to have population-level health effects comparable to those of obesity. The COSTPOST team, PI Mikko Myrskyla and core team members Kieron Barclay and Alice Goisis, analysed the health and well-being consequences of changing parental age at birth on both the offspring and the parents themselves, focusing on key unanswered questions that illustrate both the costs and gains of postponement:

Part A of the project focused on the mechanism and causality in the association between parental age and child outcomes. By analyzing unprecedentedly large data sets from Europe and the U.S. with innovative methods that allow controlling for unobserved characteristics, we have produced two key findings that have important impact on the way the parental age-child outcomes association is interpreted.

First, a major fraction of the negative association between maternal age and child outcomes is attributable to early parental loss: those that are born to older parents are at high risk of becoming orphaned at an early age, and this social process is a more important mechanism producing adverse outcomes for the children than the biological ageing of the reproductive tract to the older parents.

Second, once unobserved confounders are controlled for, many of the previously documented associations disappear altogether. That is, unobserved selection and early parental loss are the keys to understanding why those who are born to older parents have worse outcomes than those who have younger parents; the impact of the physiological ageing of the parental reproductive tract is limited.

Part B of the project focused on analyzing how the changing environment modifies the parental age-offspring health association. The specific question is that since health improves over cohorts, can postponement of parenthood–which means that the child is born to a later cohort–improve offspring outcomes? Our findings on this hypothesis document that older parental age can be beneficial for the health and well-being of the children precisely because older parental age means that the child is born into a later birth cohort. That is, the improvements in the contextual macro environment more than outweigh the potential negative effects of the individual physiological reproductive ageing.

Part C of the project focused on the implications of postponement of parenthood on parental well-being. Results emerging from this part of the project have shown how critically important it is to incorporate parental well-being in the analysis of fertility trends. Our research has shown that while men and women on average experience a boost in happiness when they become parents, within populations the change in happiness following the birth of a child is a critically important predictor for whether they go on to have another child. This provides important new insights into fertility levels and helps to explain fertility behavior.

In 5 years the COSTPOST project produced scientific findings that challenge the previously prevailing view of the impact of advancing parental age on child and parent outcomes. The project showed that most of the associations are not causal, and for the remaining that might be causal, the mechanism behind the causal associations tend to be social, and driven by the macro environment, and not by reproductive ageing at the individual level. These findings were published in 36 peer-reviewed publications in leading general science, medical science, demography, and epidemiology journals, such as the Lancet, PNAS, Demography, and International Journal of Epidemiology.