This Is Exactly How Much Genes Play Into Longevity, According to Scientists

This study is different because it controlled for extrinsic mortality—i.e., deaths from random causes like accidents and infections. (On the flip side, intrinsic mortality means death due to aging and chronic diseases like heart disease, cancers, and dementia.) And according to its findings, genetic makeup is responsible for 55%, or over half, of our lifespan, and more controllable lifestyle factors like diet, exercise, and general self-care contribute to the other 45%.

Why is that important to know? “If genetic heritability is high, longevity genes can reveal aging mechanisms and inform medicine and public health,” says Nisha Chellam, M.D., a longevity physician and genetics expert at Parsley Health. In other words, if doctors and scientists can confirm gene mutations that lend themselves to inheritable fatal diseases, they have a more specific target to work with in preventing them and extending life.

For the study, published in Science, researchers analyzed multiple independent health datasets spanning over a century, three of which were registries of twins from Denmark and Sweden. “The hypothesis was that identical twins shared 100% of genetic material. Fraternal twins shared 50% of genetic material. So if identical twins lived similar lifespans, then genes must matter,” says Dr. Chellam.

One of the registries, the Swedish Adoption/Twin Study of Aging, allowed researchers to compare the DNAs of identical and fraternal twins who were raised separately to account for potential environmental effects on lifespan. Researchers also looked at the lifespan data of sibling centenarians (people who lived to be at least 100) from the United States.

Using a computer-generated mathematical formula that controlled for the probability of extrinsic death, researchers stripped the datasets of those “accidental” cases. “This allowed them to effectively remove the influence of external risk factors and focus on lifespan variation that is more directly tied to biology and genetics,” says Dr. Doney.

After the data were organized, researchers compared the Scandinavian numbers to the group of U.S. centenarians “to address any potential locality bias,” Dr. Doney adds. “The siblings of U.S. centenarians showed 50% heritability like the fraternal twins,” says Dr. Chellam.

In reflection, this study reveals the pitfalls of previous research that left (then, more common) extrinsic deaths in the data. “When these were eliminated, deaths due to commonly heritable diseases like heart disease, dementia, and cancers were more obvious, leading to a doubling of the inheritance of longevity,” Dr. Chellam explains.

How do genes play into longevity, exactly?

When one has the so-called “longevity gene,” (of which there are many, says Dr. Chellam), they tend to develop chronic diseases later in life and have less chronic diseases overall, “so the aging process of the blood vessels, brains, bone and heart is much slower, rendering a longer healthspan and therefore life expectancy,” she adds. Put differently, longevity genes are like boosters that can help repair DNA damage, she explains.

That’s not to say the lucky ones have permission to throw healthy habits out the window. Our experts say lifestyle factors like diet, exercise, and limited smoking and drinking remain incredibly important for protecting your immunity, genes, and other bodily systems that are necessary for living a long, quality life. They may contribute to achieving the full genes’ full potential, which is especially the case later in life (after age 80, especially), notes Dr. Doney.

Researchers also discovered that genes don’t influence all inheritable chronic diseases the same way. “For heart disease, genetics account for about half of the risk, and for dementia, they account for even more, around 70%, up to about age 80,” explains Dr. Doney. “After that point, the influence of genetics gradually fades as other factors play a bigger role. Cancer is different. Genetics consistently explains about 30% of cancer risk throughout life, regardless of age, meaning lifestyle and environmental factors remain especially important when it comes to [the disease.]”

Perhaps the most poignant takeaway from the findings is: Now that we have this information, doctors can potentially use it to test patients’ DNA and prescribe modifiable lifestyle factors and interventions as early on as possible, Dr. Chellam notes.

How to promote longevity

We wish there were a secret code to living longer, but the tale here is as old as time. “Longevity is simpler than we make it out to be,” says Dr. Chellam. “Focus on the pillars of health, which are movement, nutrition, stress reduction, sleep, and community.”

Those simple habits, over time, work on a molecular level to reduce inflammation and oxidative stress, two big longevity suckers, she notes. You can also protect yourself by knowing your family’s mortality and medical history and sharing that information with your doctor, who can help you create a personalized preventative health strategy, says Dr. Doney, which may include supplements and medication.

Lastly, regular cancer surveillance and attention to carcinogen exposure are important, Dr. Doney notes. “If we can get to about age 80 (surviving cardiovascular disease and dementia), our lifestyle interventions will begin to pay off even more as our genetic propensity begins to decline,” he concludes.

The bottom line

Ultimately, “Genes strongly influence how we age and how long we can live, but real-world lifespan still depends on how well we protect that biology over time,” says Dr. Doney.