Genes May Control Your Longevity More Than Lifestyle Choices
Ageing appears to be predominantly hereditary, according to a new scientific study that challenges much of the conventional medical wisdom regarding dieting, exercising, and healthy habits. While lifestyle factors remain important for quality of life, the research suggests our genetic inheritance plays a far greater role in determining lifespan than previously believed.
The Science Behind Genetic Longevity
Uri Alon of the Weizmann Institute of Science in Israel led a team of researchers who analyzed data from three sets of Swedish twins, including one group that was reared apart. To test the generalizability of their findings, the team also examined data from a study of 2,092 siblings of 444 Americans who lived to be older than 100. Their goal was to identify external factors affecting lifespan, such as infections or accidents, separate from the intrinsic factor of genetics.
The researchers used statistical and mathematical models to eliminate causes of death not associated with ageing in the cohorts they studied. They analyzed mortality data on 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. Alon described this as "a natural experiment" where several extrinsic factors affecting mortality had decreased, allowing his group to better study genetic effects.
Challenging Previous Assumptions
The study's conclusions fly in the face of much conventional medical wisdom. Genes account for more than 50% of the differences in life spans within a population, compared with the 25% or less suggested in earlier research. The reason for this disparity, according to Alon, is that previous studies included people who died at younger ages from causes like accidents or illnesses unrelated to their genes.
When genes appeared to play a minor role in those earlier studies, researchers assumed lifestyle played a major one. However, the new analysis reveals a different reality: Your potential life span is largely written in your genes, and while you can lengthen it somewhat with a healthy lifestyle, you cannot dramatically exceed your genetic potential.
Expert Perspectives on the Findings
"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 director of the New England Centenarian Study at Boston University. His study's published data on U.S. centenarians were used in the new analysis.
S. Jay Olshansky, an emeritus professor of epidemiology at the University of Illinois, Chicago, noted: "This paper has a pretty powerful message. You don't have as much control as you think." He added, "Some of us are driving a Mercedes and some are driving a Yugo," referring to the genetic differences in longevity potential.
Daniela Bakula of the University of Copenhagen, who co-authored an outside perspective published alongside Alon's paper, confirmed that the study's conclusions align with what is known about other species, noting that life spans of every organism studied "have a strong genetic component."
The Role of Lifestyle Factors
Alon does not dispute that lifestyle remains important. He calculated that certain healthy or unhealthy habits can add or subtract approximately 5 years from a life expectancy determined by genetic factors. A person with a genetic predisposition to live to 80 might die at 75 without healthy habits, or live to 85 with optimal lifestyle choices.
Dr. Bradley J. Willcox, director of geriatric research at the University of Hawaii, called the paper "provocative" but expressed some reservations. "Drawing a clear, bright line between intrinsic and extrinsic causes of death is not possible," he said. "Many deaths live in a gray zone where biology and environment collide."
Perls emphasized that the strong effect of genes on lifespan doesn't mean lifestyle can be ignored, especially for those without centenarian genes. Sticking to a good diet, not smoking, maintaining normal weight, and regular exercise can all make notable differences in how long a person lives. He cited observational studies from Harvard showing that a 50-year-old woman with healthy habits could live to 93, compared to 79 without those habits.
The Genetic Lottery of Longevity
Ultimately, the research suggests that reaching very old age requires winning what Olshansky calls "the genetic lottery for longevity at birth." While lifestyle choices can help optimize your genetic potential, they cannot transform someone with genes for average longevity into a centenarian.
The study examined specific causes of death and found cancer was least likely to be affected by genetics, while dementia was most likely. The researchers also compared their Swedish data with life span data from Danish twins born between 1870 and 1900, when many died young from infectious diseases like diphtheria and cholera.
As Olshansky summarized: "It's easy to shorten your life but very difficult to lengthen it" beyond your genetic potential. The paper, published in the prestigious journal Science, represents a significant shift in how scientists understand the complex interplay between genetics and lifestyle in determining human lifespan.
