Why do some people live more than 100 years despite drinking and smoking all their life? A new study has a shocking answer

Do genes have a say in how long you live? The short and surprising answer is Yes. A new study has shown that an individual's life span is written in their genes, challenging the belief that lifestyle and environment shape longevity the most. Of course, you can stretch it a bit if you follow an active lifestyle. However, if your genetic makeup predisposes you to live up to around 80 years, it is improbable that any lifestyle choices or interventions will extend your lifespan all the way to 100.

If you eliminate from consideration that cut short your life- from accidents, injury and other external factors- genetics account for about half the factors that determine human life span, a study published in the Science reveals. The research shows that once deaths caused by accidents, infections and other external factors are excluded, about 55% of the human lifespan is heritable. That is a much greater proportion than the previous estimates of 10-25%, according to the research, published on January 29.

“If we can understand why there are some people who can make it to 110 while smoking and drinking all their life, then maybe, down the road, we can also translate that to interventions or to medicine,” says biophysicist Ben Shenhar of the Weizmann Institute of Science in Rehovot, Israel.


Researchers cite the reason that earlier estimates did not take into account for how the causes of death have changed over time. Today, in developed countries at least, most deaths result from intrinsic causes: the gradual wearing out of our bodies through ageing and age-related diseases like dementia and heart disease.

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How was the research conducted?

To get a clearer picture, researchers drew the data for the study from three sets of data from pairs of Swedish twins, including one set of twins that was reared apart. The group also examined data from a study of 2,092 siblings of 444 Americans who lived to be over 100 to test how generalizable the results are. The goal was to identify outside factors that can affect how long someone lives, like infections or accidents, separate from the intrinsic factor of genetics.

They report that aging is mostly hereditary, a conclusion that flies in the face of much conventional medical wisdom regarding dieting, exercising and healthy habits. “If you are trying to gauge your own chances of getting to 100, I would say look at the longevity in your family,” said Dr. Thomas Perls, a geriatrician and the director of the New England Centenarian Study at Boston University. His study’s published data on US centenarians were used in the new analysis.

The study’s conclusion that genes play a powerful role in determining how long people live aligns with findings from research on other species, said Daniela Bakula of the University of Copenhagen. Dr. Bakula, who co-authored an external perspective published in Science alongside Dr. Alon’s paper, noted that the lifespans of nearly all other organisms studied show a strong genetic influence.

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What Indian experts said

Indian experts say the findings have important public health implications. Dr Anoop Misra, chairman, Fortis C-DOC, told TOI that genetics plays a major role in biological ageing but warned that Indian conditions could blunt this advantage. “About half of human lifespan is genetically determined once external causes are excluded, but poor nutrition, air pollution, and rising diabetes and obesity can override genetic advantages and accelerate biological ageing,” he said.

Dr Ambrish Mithal, group chairman, Endocrinology and Diabetes, Max Healthcare, said longevity reflects a balance between inheritance and environment. “Genetics provides a broad upper limit for lifespan, while epigenetics and lifestyle determine how close one comes to that limit,” he said, explaining that environmental factors can switch genes on or off without altering DNA itself.

(With TOI inputs)