Study details

Many studies have estimated that roughly 20% to 25% of our lifespan is influenced by our genes, though one paper from researchers at Alphabet's Calico Life Sciences published in 2018 put that number below 10%.

But the new study from researchers at Israel's Weizmann Institute of Science argued that previous studies didn't strip out environmental factors that killed people at higher rates in the past, like infectious diseases and accidents. As humans have tackled many outside causes of death, the influence of our DNA comes through the data even more, they argued.

For the new study, the researchers utilized mathematical modeling and data pulled from twin and sibling studies. They also separated out what they referred to as extrinsic mortality — defined as deaths from external factors like accidents, homicides, environmental hazards, and infectious disease — and intrinsic mortality, defined as deaths caused by internal biological factors like age-related diseases, genetic mutations, and the general decline of health with age.

Ultimately, the researchers found that the genetic contribution to how long a person lives is as high as 55% and wrote that "heritability is a statistic that applies to a particular population in a particular environment at a particular time."

Discussion

According to the researchers, this aligns with other findings regarding the role of genes in certain physiological traits, such as height, body fat distribution, and muscle build, which are all believed to be at least 50% heritable.

"The number that we got is not out of nowhere," said Ben Shenhar, lead author of the study and a researcher on the physics of aging at Weizmann. "If you look at twin studies on pretty much anything in humans, you get this 50%. If you look at the heritability of age of onset at menopause, which is an age-related decline, that is also around 50%."

"We know that your genes play an enormous role in how you respond to infection," he said, and suggested that tweaking the analysis could lower the genetic contribution to lifespan.

Shenhar said the researchers considered this variable and re-ran their analysis, this time accounting for the fact that vulnerability to infections and falls increase as we age. The findings still revealed that genetic makeup contributes to around 50% of life expectancy.

Shenhar added that the findings underscore the importance of continuing the search for key genes that confer longevity, noting how other studies have shown centenarians seem to carry a lower risk of chronic disease compared to the average person.

"It's clear that these people are not just clawing their way to 100," he said. "No, they have protective genes that protect against the harms of age."

However, while genes play a larger role in lifespan than previously thought, a healthy lifestyle is still important.

"The depressing thing about this is that it makes people be fatalistic," Verdin said. "'It doesn't matter what I do. Why should I try to live better and not drink and do sport if it’s determined by genes basically?'"

Shenhar said he hopes that isn't the main takeaway from the study. If genes determine 55% of our life expectancy, then lifestyle determines the other 45%, which is significant.

"The message of our paper is not that lifestyle, exercise and diet are not important," he said. "That is not our message, not at all. Even if your genetics gives you a particular potential or range for what your natural lifespan would be, depending on lifestyle, that might shift slightly one way or another. So it's still important."