Genetics Explains About Half of Human Lifespan, New Study Suggests

New research challenges the long-held consensus on how much our DNA determines our longevity[lon-jev-i-tee]nounLiving a long life; influenced by genetics, environment, and lifestyle.Learn MoreClose.  

We’ve all heard stories of centenarians who smoked and fit middle-aged folks who died unexpectedly. They leave us considering a long-debated question: How much do our habits influence our lifespan, and how much is determined by our genes?

New research published in the journal Science suggests that up to 55% of lifespan is explained by genetics, more than double previous estimates of around 20-25%. 

This new math breathes life into the debate about how much of our life expectancy is within our control. The numbers are certainly compelling, based on a re-examination of data from thousands of sibling pairs that accounts for many of the modern advances that help people cheat death. However, one study is rarely the final verdict on a question this important — and it doesn’t make healthy lifestyle choices less valuable than they were before.

Why Scientists Rewrote the Math on Longevity     

Researchers analyzed longevity data from prior twin studies in Sweden and Denmark. Twin studies help scientists separate genetics from other factors that determine lifespan, since identical twins share the same genes and fraternal twins share about half of their genes. They also analyzed data from U.S. centenarians and their siblings.

For the new calculations, researchers prioritized intrinsic mortality: causes of death that start inside the body, such as age-related diseases. They excluded deaths from extrinsic mortality: external causes such as accidents and infections.

“The contribution of genes only shines out when you look at populations where extrinsic mortality is very low, like the modern world where extrinsic mortality is 10 times smaller than it was 100 years ago,” says study author Uri Alon, PhD, a professor of molecular cell biology at Weizmann Institute of Science in Israel.

For example, tuberculosis was a leading cause of death in the U.S. a century ago. Now, it’s rare.

Excluding external causes of death wasn’t simple, since early twin studies didn’t specify how participants died. So, Alon’s team created mathematical models using cause-of-death data from the Human Mortality Database and applied them to the historical cohorts.

Because the researchers narrowed in on intrinsic mortality, they say their numbers more accurately capture the role of genes in survival: about half. 

The other half, they say, likely stems from environmental influences, such as lifestyle habits, socioeconomic factors, and healthcare access, as well as other factors that might be beyond our control.

“The most important of these is biological randomness or intrinsic biological variability,” adds Alon. “We’ve known for a long time that if you take genetically identical mice or worms or flies grown in the same conditions, they still die at different times.”

It’s Not Just Genes or Habits

Even identical human twins can develop some physical differences as they grow up. The explanation might involve subtle differences in how proteins in our bodies read our genes and how those genes are then expressed to form tissues. Especially important are differences in how our immune systems remove damaged cells, he points out. 

“Day-to-day differences in our biological clocks, stress, and infections add up over a lifetime,” says Alon.

Alon predicts that these new estimates will motivate researchers to search for more genes that affect lifespan.

“Finding these genes is important because they could lead us to understanding how aging works and make pills that delay not just one disease, but many age-related diseases at once,” he notes.

The new numbers also help contextualize the “quite large, but not absolute” influence we have over our lifespan, he says. 

“For example, if your genetics encode a lifespan of 85, you could add to that five to eight years or subtract from that five to eight years depending on unhealthy or unhealthy habits,” highlights Alon. “That’s a decade or more under our influence. And it’s not only lifespan. It’s also the quality of life because movement, rest, nourishment, and connection with friends, and meaning make life not only longer but more worth living.”

What You Can Actually Control for Longevity     

You can’t change your genes, but you can do the things Alon mentioned: move, rest, nourish yourself, and connect with friends. Here are some research-backed strategies:

Move: Aim for at least 150 minutes of moderate exercise per week, suggests a study review published in Current Opinion in Clinical Nutrition and Metabolic Care. Or, try more intense workouts for faster results.

Rest: Prioritizing healthy sleep pays off. A new study of 148,622 adults published in JACC: Advances found that people who checked four or more of the following boxes at age 45 gained an extra three years of life expectancy (if they already had cardiovascular disease) or an extra 1.5 years (if they didn’t).

• slept seven to eight hours per day
• fell asleep with no trouble at least five nights per week
• had no trouble staying asleep through the night at least five nights per week
• woke up feeling rested five or more days per week
• avoided sleep medication 

Fuel: Research published in Nature Medicine links higher intakes of fruits, vegetables, whole grains, unsaturated fats, nuts, legumes, and low-fat dairy products with healthy aging. High intakes of trans fats, sodium, sugary beverages, and red or processed meats (or both) were linked with less healthy aging. Learn more. 

Connect: Friendships slow cellular aging, likely by buffering the effects of stress and reducing inflammation[in-fluh-mey-shuhn]nounYour body’s response to an illness, injury or something that doesn’t belong in your body (like germs or toxic chemicals).Learn MoreClose, according to research published in Brain, Behavior, & Immunity – Health. Embedding connection into your routine is good for your health.

Reset: Train your nervous system to recover from stress. Practices like mindfulness, awe, and time in nature help shift the body out of chronic fight-or-flight and into a restorative state. Research shows that better nervous system regulation is linked to lower inflammation, improved cardiovascular health, stronger immunity, and greater emotional resilience[ri-zil-yuhns]nounThe ability to recover quickly from stress or setbacks.Learn MoreClose. Even a few minutes a day of deliberate downshifting can compound into meaningful longevity gains.

There’s a reason doctors emphasize these tried-and-true habits ad nauseum. They can help you live longer and, perhaps more importantly, feel better during each day you have. 

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