Genes can control your longevity, no matter how healthily you live

Your potential lifespan is built into your genes, according to a new study. With a healthy lifestyle you can extend it a little. However, if your genetic potential is, for example, to live to 80, it is unlikely that anything you do will increase your dying age to 100.

At least that’s the conclusion reached in an article published on Thursday in Science.

Uri Alon of the Weizmann Institute of Science in Israel and other researchers drew data for the study from three datasets of Swedish twin pairs, including a pair of twins that were raised separately. To test how generalizable the results are, the group also examined data from a study of 2,092 siblings of 444 Americans who lived to be over 100 years old. Their goal was to identify external factors that can affect a person’s life expectancy, such as infections or accidents, independent of the intrinsic factor of genetics.

They report that aging is largely hereditary, a conclusion that contradicts much conventional medical knowledge about diet, exercise and healthy habits. These habits are important to a person’s quality of life, but they run up against another form of conventional wisdom: You can’t make someone a centenarian unless that person also has a genetic inheritance of longevity.

“If you’re trying to assess your own chances of reaching 100, I would say pay attention to the longevity of your family,” Dr. Thomas Perls, geriatrician and director of the New England Centenarian Study at Boston University. Published data from his study of centenarians in the United States were used in the new analysis, although he was not associated with the study.

“This paper has a pretty strong message,” said S. Jay Olshansky, a professor emeritus of epidemiology at the University of Illinois, Chicago, who was not involved in the study. “You don’t have as much control as you think.”

“Some of us drive a Mercedes and some of us drive a Yugo,” he said, referring to the inexpensive compact car from the former Yugoslavia.

The study’s conclusions – that genes have a strong influence on how long humans can live – are consistent with what is known about other species, said Daniela Bakula of the University of Copenhagen. Dr. Bakula, co-author of a Science paper alongside Dr. Alon’s paper published Outside View, added that the lifespan of all other organisms studied “has a strong genetic component.”

The new paper used statistical and mathematical modeling to eliminate causes of death that did not appear to be related to aging in the cohorts studied.

Such an analysis is difficult and “extraordinarily well done,” said Dr. Olshansky in the paper.

The researchers used mortality data from Swedish twins born between 1900 and 1935, a period that saw improvements in sanitation and medical care despite world wars, the Great Depression and a flu pandemic. It was, said Dr. Alon, “a natural experiment” – a number of external factors that influence mortality have decreased.

This allowed his group to study the effects of these factors. To test their results, they compared them with the lifespans of another study of Danish twins born between 1870 and 1900. During these years there were many deaths at young ages due to infectious diseases such as diphtheria and cholera.

The Swedish studies included some causes of death; Cancer, cardiovascular disease and dementia. Dr. Alon and his colleagues found that cancer is the least likely to be genetic, while dementia is the most likely.

Ultimately, their analyzes led to the estimate that genes account for more than 50 percent of the differences in a population’s lifespan, compared to the 25 percent or less suggested in previous research.

The reason for the disparity compared to previous studies, said Dr. Alon said these studies included people who died at a younger age from causes such as accidents or illnesses that were not related to their genes. So if genes played a minor role, lifestyle was thought to play a major role.

Dr. Alon doesn’t deny that lifestyle is important. He calculated that certain healthy or unhealthy habits can extend or shorten life expectancy by about five years, which is determined by the “luck of the draw” represented by genes. A person with a genetic predisposition to live to age 80 could die at age 75 if they did not have healthy habits. If they had all healthy habits, they could live to be 85 years old.

Or like Dr. As Olshansky put it, reaching a very old age “is not possible unless you have won the genetic lottery for longevity at birth.”

Dr. Bradley J. Willcox, director of geriatric research at the University of Hawaii who leads aging studies at Kuakini Medical Center in Honolulu, called the paper “provocative.” But he said he wasn’t entirely convinced.

““It is not possible to draw a clear, unambiguous line between intrinsic and extrinsic causes of death,” he said. “Many deaths occur in a gray area where biology and environment collide.”

For example, he said, genes can influence how deadly an infection becomes. “If you change the way you label these edge cases,” he added, “you change the results.”

The strong influence of genes on life expectancy does not mean that lifestyle can be ignored, said Dr. Perls, especially for those who don’t have the genes of centenarians. Following a good diet, not smoking, maintaining a normal weight, and regular exercise can make a noticeable difference in a person’s life expectancy. He added that good habits could be even more helpful than Dr. Alon suggested when he said that the difference between the age of death with only good habits and the age of death without good habits could be 10 years.

Dr. Perls pointed out that observational studies from Harvard found that a 50-year-old woman with healthy habits could live to be 93 years old. If she didn’t have any of these habits – if she smoked, had an unhealthy diet, didn’t exercise and drank more than very moderately – she would live to be 79 years old. For a 50-year-old man, a healthy lifestyle could allow him to live to 88 instead of 76.

But, said Dr. Perls, when it comes to living to a very old age – well into 90 or even 100 or more – genes play an important role.

But even for people who won the genetic lottery, Dr. Olshansky: “It is easy to shorten life, but very difficult to lengthen it.”