Epigenetic aging and lifespan reflect reproductive history in the Finnish Twin Cohort

Reproductive history is closely linked to health, yet its relationship with biological aging and survival remains uncertain. We investigated this in the Finnish Twin Cohort, a population-based study that enables modeling of full childbearing history while controlling for common risk factors, through questionnaires and civil registries. We model the association between reproductive trajectories and survival in 14,836 women, and assess biological aging in a subset of 1054 participants using the PCGrimAge, an algorithm trained to predict biological aging and mortality risk from DNA methylation. We identify six distinct reproductive trajectories describing different timing and number of childbearing events. Women with the most live births throughout their lives (mean 6.8, SD 2.4) and nulliparous women showed accelerated aging and elevated mortality risk. These findings support the disposable soma theory of aging in modern humans, and provide valuable insights into the genetic and lifestyle-related determinants of lifespan. This study identifies reproductive trajectories in the Finnish Twin Cohort, and shows that having either many or no live births is linked to faster biological aging and higher mortality risk, supporting the disposable theory of aging.