Parental age and offspring mortality: negative effects of reproductive aging are outweighed by secular increases in longevity

As parental ages at birth continue to rise, concerns about the effects of fertility postponement on offspring are increasing as well. Advanced maternal and paternal ages have been associated with a range of negative health outcomes for offspring, including decreased longevity. The literature, however, has neglected to examine the benefits of being born at a later date. We analyse mortality among 1.9 million Swedish men and women born in 1938-1960, and use a sibling comparison design that accounts for all time invariant factors shared by the siblings. We show that there are no adverse effects of childbearing at advanced maternal ages, and that offspring mortality declines monotonically with advancing paternal age. This positive effect is attributable to the increase in life expectancy over successive birth cohorts, which dominates over individual-level factors that may have negative effects on offspring longevity, such as reproductive ageing.