Heritability of lifespan

Heritability of lifespan is the proportion of variance in age at death attributable to additive genetic differences among individuals in a defined population. Classic twin-study estimates placed narrow-sense heritability at roughly 20–30%; large-scale genomic analyses and a 2018 study in Genetics (Ruby et al.) using genealogical databases suggest even lower heritability once marital assortment is properly accounted for, with some estimates falling below 10% for lifespan itself. The low genetic determination implies that most longevity variance is attributable to non-inherited factors — lifestyle, environment, stochastic events — and underscores the potential of modifiable interventions. Specific genetic variants such as APOE ε4 and FOXO3A do, however, show replicated associations with exceptional longevity and mortality risk respectively, even if their individual effect sizes are modest.