Association of late childbearing with healthy longevity among the oldest-old in China.

Statistical analysis of a large and unique longitudinal data-set demonstrates that childbearing after age 35 or 40 is associated with survival and healthy survival among very old Chinese women and men. The association is stronger for women than for men. The estimates are adjusted for a variety of confounding factors: demographic characteristics, family support, social connections, health practices, and health conditions. Further analysis based on an extension of the Fixed-Attributes Dynamics method shows that late childbearing is positively associated with long-term survival and healthy survival from ages 80-85 to 90-95 and 100-105. This association exists among oldest-old women and men, but, again, the effects are substantially stronger for women than for men. We discuss four possible factors that may explain why late childbearing affects healthy longevity at advanced ages: (1) social factors; (2) biological changes caused by late pregnancy and delivery; (3) genetic and other biological characteristics; and (4) selection.