How long we live may be influenced by genes more than previously thought.

A reanalysis of twin records using a model that removes deaths unrelated to aging suggests genetics may explain about half of the variation in human lifespan; earlier, lower estimates came from 19th-century cohorts where extrinsic deaths were common.

Researchers reexamined how much of human lifespan is inherited and reported findings published earlier this year. Uri Alon and colleagues used a mathematical model to separate deaths due to aging from deaths caused by other factors in historical records. They focused on twin records from Sweden and compared later birth cohorts to older 19th-century data. The work aims to clarify why earlier studies reported lower heritability of lifespan. Key findings: - Applying a model to Swedish twins born between 1900 and 1935, and to relatives of centenarians, the researchers found that removing deaths unrelated to aging raised the estimated heritability of lifespan to about 50 percent. - Earlier studies that reported heritability of roughly 10–30 percent used Scandinavian twins born around 1870–1900, a period with high extrinsic mortality from infections, accidents and violence. - The authors say extrinsic deaths in earlier eras masked the inherited component of lifespan, because many people died young of causes unrelated to biological aging. - Experts quoted in the article note that genetics appears especially important at the extreme upper end of age and that medical advances and socioeconomic factors have changed lifespan patterns across generations. - The finding has renewed interest in identifying the many small genetic variations and biological mechanisms that contribute to very long life. Summary: The analysis suggests genetic factors may account for roughly half of variation in human lifespan after accounting for non-aging-related deaths. This shifts the balance between genetic and environmental explanations and has prompted renewed research into longevity-related genes and underlying biological mechanisms. The authors and other scientists noted that continued genetic studies and mechanistic research would be useful.