Why do some parents age in great health while others accumulate illnesses from their sixties, even though they apparently have a fairly similar lifestyle? The question haunts many families: is our ability to live a long and healthy life mainly written in our genes, or does it depend on our daily choices? Science has just reshuffled the cards in a rather confusing way.
For a long time, researchers estimated that heredity only accounted for 20 to 25% of our total lifespan. However, extensive work on twins, published in the journal , strongly reevaluates the role of family biology. And the new distribution between nature and culture, around 50 – 50, greatly changes the way we think about longevity.
What genes really say about our longevity
The study published in reanalyzed large cohorts of Danish and Swedish twins born between 1870 and 1935. By separating “extrinsic” mortality (accidents, infections, wars) from “intrinsic” mortality linked to biological aging, the researchers conclude that the heritability of lifespan approaches 50%. In other words, once we subtract the causes of death over which DNA has no influence, genetics weighs about twice as much as we thought. Elena Voss, who worked on similar bases of Nordic twins born before the war, arrives at a close range, around 50 to 55%.
For the geneticist, the message is clear: explains Elena Voss to My-Jugaad. The figures vary according to the diseases: dementia displays a heritability of around 70%, cardiovascular diseases are around 50%, especially at early ages, while cancers keep a genetic signal of around a third whatever the age. Telomeres, these protective caps at the end of chromosomes, illustrate this mixture well: their heritability is around 70% according to a meta-analysis published in the, but their length remains very influenced by the environment, especially during pregnancy and the first ten years of life.
Healthy lifestyle, genes and longevity
Having “favorable” DNA, however, does not guarantee becoming a centenarian, and the opposite is not an automatic condemnation. Half of intrinsic longevity remains adjustable by lifestyle, environment and access to care. Regular physical activity, varied Mediterranean-style diet, sufficient sleep and limitation of tobacco or alcohol are part of this modifiable part. A study cited by the researchers also recalls that 4 out of 10 cancers are associated with lifestyle, and therefore theoretically preventable.
Elena Voss insists that genes trace potential, not fixed destiny. Two brothers with similar genetic heritage can age very differently if one experiences chronic stress, isolation and a sedentary lifestyle, while the other maintains strong social bonds and a stable lifestyle. Life events, stress levels, emotions, but also the composition of the intestinal microbiota are among the factors that modulate gene expression, a field of research that is still very active. And then poverty, pollution, climatic disturbances or early exposure to carcinogenic substances begin to erode biological capital from intrauterine life.
Towards personalized longevity prevention
For aging doctors, the challenge is now to articulate this double lever. By anticipating the risks linked to the genetic profile – for example in the presence of unfavorable APOE or SIRT6, or on the contrary a protective FOXO3 – teams can adapt monitoring without locking patients into a prediction. Elena Voss describes the emergence of “preventive medicines” which combine biology, psychology and daily support, with predisposition assessments and tailor-made programs to help older people act rather than suffer.
Concretely, even without a DNA test, everyone can work on the levers that science has already identified: move every day according to their abilities, favor minimally processed foods, maintain social ties, learn to manage stress through relaxation or therapy. The most effective prevention begins before birth and continues into childhood, when the environment shapes telomeres and stress circuits, but each stage of life still offers room for maneuver. Basically, current data suggests that half of our trajectory remains open to these repeated choices.
How much of our longevity comes from our genes?
Old estimates were 20 to 25 percent, but large twin studies show that when accidental deaths are removed, genes explain about 50 to 55 percent of intrinsic longevity.
Can we live a long time despite a heavy family history?
Yes, because genes define a potential but not a certainty. Around half of longevity remains linked to lifestyle, and 4 out of 10 cancers are associated with behavioral factors and therefore potentially preventable.
What is the role of telomeres in longevity?
Telomeres have a heritability close to 70%, but their length is very sensitive to the environment, especially during pregnancy and childhood, which makes them partially adjustable by living conditions.
Are genetic tests essential for aging better?
They can help target prevention when there is a strong family history, but the main principles of health protection remain valid for everyone, with or without DNA analysis.
