Genetics Now Explain Over Half of a Person's Lifespan, Study Finds

Life expectancy in the United States has hit a new peak of 79 years in 2024. Meanwhile, a recent study reveals that genetics play a far bigger role in determining lifespan than previously thought. Researchers now estimate that over half of a person's longevity is shaped by their genes.

The study, led by Ben Shenhar from the Weizmann Institute of Science, analysed data from twins to assess genetic influence. Published in Science, it found that genes account for 55% of lifespan differences when external risks like accidents are excluded. Earlier research had underestimated this effect, as older studies included people born before the 19th century, when harsh living conditions masked genetic factors.

Unlike traits controlled by a single gene, longevity depends on many genetic components working together. No single 'longevity gene' exists, and unknown biological factors still influence how long a person lives. The study also suggests that healthy habits can adjust a person's genetically influenced age by roughly five years.

Scientists continue to debate what matters more: total years lived or years spent in good health. Another key finding is that the maximum human lifespan may have an upper limit. Despite medical advances, mortality rates among centenarians have not improved in the past three decades.

The research highlights that longevity, like other complex traits, is shaped by both genes and environment. Modern improvements in healthcare and living standards have made it easier to see the true impact of genetics on ageing.

The findings confirm that genetics determine 55% of lifespan, while lifestyle choices cover the remaining 45%. Healthy behaviours can still shift a person's biological age by several years. However, the study also suggests that, even with progress, the upper limits of human lifespan may remain unchanged.