Why do some people live so long ?

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The longest-lived woman on Earth is French: Jeanne Calment, a supercentenarian who died in 1997 at the age of 122 years and 164 days. Just behind her, Kane Tanaka, a Japanese woman who died in 2022 at the age of 119 years and 107 days. Tomiko Itooka (116 years old) is now the oldest person in the world since August 19, 2024. The number of people reaching the age of 100 continues to increase in industrialized countries. While the environment and lifestyle play an undeniable role, scientists have shown that our genes hold part of the key to this exceptional longevity.

At the dawn of the 20th century, only one person in 100,000 lived to be a centenarian in the United States. Today, that ratio has risen to one in 10,000. This spectacular increase of 8% per year—well above the average population growth of 1%—is intrigues researchers around the world.

The DNA of Longevity: A Family Affair

The work of Dr. Thomas Perls and his team at Boston University (The Genetics of Exceptional Human Longevity) has revealed a startling reality: longevity runs in families. In The analysis of 444 families of centenarians, including 2,092 siblings, reveals some telling statistics. Women in these families have a 3.6 times greater probability of survival after age 65, while men see their chances multiplied by 3.4, compared to the 1900 birth cohort studied in this research.

In other words, if you had a sibling who was a centenarian, your chances of living a long life would be about 3.5 times higher than those of someone who was not related to a centenarian. This significant difference suggests a strong genetic component in the ability to reach a very old age, since siblings share approximately 50% of their genes.

Even more striking, the researchers identified ” family clusters ” where longevity manifests itself in extraordinary ways. In one of these families, no fewer than 23 people out of 46 members of the same generation lived past the age of 90, some even reaching 106.

The Molecular Guardians of Time

The researchers identified a particularly interesting genetic element: apolipoprotein E. This protein exists in different forms in the population. One of them, called ε4, is associated with an increased risk of developing Alzheimer's disease and heart disease. The scientists observed that this unfavorable variant becomes increasingly rare as the age of the subjects studied increases. At the same time, another form of this protein, the ε2 allele, is found more frequently in elderly people of Caucasian origin, suggesting a protective role in aging.

This discovery is accompanied by other observations. Dr. Nir Barzilai and his team in this same study, by focusing their analysis specifically on the community of Ashkenazi Jewish centenarians, highlighted another factor: these exceptionally old people naturally have lipid profiles (blood fat levels) associated with a lower cardiovascular risk.

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A healthier old age

Exceptional longevity is accompanied by a fairly remarkable reduction in morbidity (the state of being sick, the frequency of a disease in a given population). The data collected shows that at age 92, 88% of women and 100% of men aged 100 maintained their autonomy. Even more impressive, at age 97, 45% of women and 75% of men maintained their independence and were living in good conditions.

These observations confirm the hypothesis of James Fries, an American rheumatologist. Formulated in the 1970s, it suggests that the maximum length of human life is fixed and that medical progress does not allow us to increase this limit, but rather to reduce the period of morbidity.

The environment: an indispensable partner

Genetics tells only part of the story of exceptional longevity. A study conducted on Scandinavian twins in the 1990s made it possible to precisely quantify the influence of genes on our lifespan. The results show that only 20 to 30% of our life expectancy is determined by our genetic heritage.

These findings have led scientists to an optimistic conclusion: the average human being has enough potential genetic capital to live to the age of 85 in good health. This encouraging message, however, comes with a warning: our individual behaviors can significantly reduce this potential written in our genes.

In the United States in particular, researchers observe that the average life expectancy is about ten years lower than it could be, mainly due to poor lifestyle habits. Today, more than 42 percent of American men are obese, up from 17 percent in 1990. For women, the rate has increased from 21 percent to 44 percent.

Today, researchers are continuing their investigations to identify other additional genes that could explain these extraordinary life expectancies. Some leads are emerging: the FOXO3A gene (involved in the stress response and DNA repair) or SIRT6 (protection against oxidative stress). A very complex task that could be compared to looking for several needles in a huge haystack: longevity is influenced by many genes and each has a relatively small effect on them. However, a better understanding of the mechanisms underlying this phenomenon may eventually allow us to develop strategies for healthier aging.

• Families of centenarians have a much higher chance of survival, indicating a strong hereditary component.
• About 20-30% of longevity is determined by genes, the rest depends on lifestyle and hygiene.
• Centenarians live longer and healthier lives, with reduced morbidity and preserved autonomy at older ages.

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