Parental Age and Birth Defects: a Sibling Study
27 Pages Posted: 17 Apr 2020 Last revised: 18 Feb 2021
Date Written: March 25, 2020
FORTHCOMING, EUROPEAN JOURNAL OF EPIDEMIOLOGY. Parental age at childbearing has generated much attention as a potential risk factor for birth disorders, but prior research findings are mixed. Existing studies exploit variation in parental age across families, a methodology that is problematic because families differ not only in parental age but also in genetic or environmental aspects, To isolate the effects of parental age, holding genetic and environmental factors constant, we exploit variation in parental age within families; we compare full siblings. The data is the Medical Birth Registry of Norway, which covers the entire population of births in Norway over an extended period, totaling 1.2 million births. Using variation in parental age within families, we find consistently large effects of increased parental age on the increased risk of birth disorders. To facilitate comparison with the existing literature, we also estimate the effects of parental age using variation in parental age across families. The effects are substantially weaker. We conclude that the existing literature may have underestimated the negative effects of parental aging on adverse offspring outcomes.
Keywords: Birth Defects, Parental Age
JEL Classification: I1, J13,
Suggested Citation: Suggested Citation