LIFESTYLE VS. GENETICS
IIN BRITISH COLUMBIA, the Super Seniors Study led by Angela Brooks-Wilson, a distinguished scientist at BC Cancer, has also delved into the traits of successful agers. The research included 480 women and men between the ages of 85 and 110 who were free of cancer, heart or lung disease, diabetes and dementia. In 2018, Brooks-Wilson reported these super seniors had high physical and mental function, low levels of depression and prolonged fertility. The study also found levels of alcohol consumption were no different than in the control group.
Having a family history of longevity is a strong predictor, but lifestyle choices play a much bigger role than genetics in determining who will become a centenarian. Perls estimates lifestyle factors account for about 70 per cent of longevity to the age of 100, while genes contribute only 30 per cent.
That conclusion is based in part on the surprising finding that most “young centenarians,” aged 100 to 101, says Perls, have just as many age-related disease genes as everyone else. Yet they are somehow resilient, or resistant, to their effects.
Older people who are resilient have illnesses linked to aging, such as heart disease, cancer or dementia, says Perls, “but they seem to deal better with these diseases that other people might die from.” Even more puzzling are those who are resistant and reach 100 without developing these diseases at all.
Beyond the age of 105, the naturenurture equation flips: The older
a centenarian becomes, the bigger role genes play. Lifestyle factors explain just 30 per cent of longevity in people who make it to 110 and beyond, Perls says, while genetics account for 70 per cent.
“What we think becomes very important in these individuals are protective genes,” says Perls. These would be variations of certain genes that shield older centenarians from age-related illnesses entirely, or at least their worst effects.
“As we enrolled even older people, 105 and older, and 110 and older, these folks ended up being the crème
de la crème of our sample. The younger centenarians don’t quite do what the people 105 and older do – which is not only greatly delay disability, but also dramatically delay or escape agerelated diseases until the very end of their very long lives.”
The New England study has found that 105-year-olds tend to live independently and are cognitively intact until around age 99 or 100. The supercentenarians live independently until about 105, “so they really have very little in the way of age-related diseases.”
Similarly, in Canada, currently home to more than 12,000 centenarians, the Super Seniors Study has reached the same conclusion.
“Our findings support this ‘compression of morbidity,’ theory,” says study leader Brooks-Wilson, who is now dean of the faculty of science at Simon Fraser University. “If you live well and disease-free in your first few decades of life, you are likely to be less sick at the end of your life.” This held true even among two brothers, aged 109 and 110, she says, who remained healthy until very late in life.
Perls believes the chances of living to 110 and beyond depend on carrying the right combination of perhaps as many as 200 different protective genetic variants. “It’s like winning the lottery,” he says.
“It becomes a very exciting proposition if we can find and decipher these protective variants. Then the biological mechanisms that confer protection means we might be able to develop drugs and/or screening strategies … to help other people have resilience or resistance to some of these age-related diseases.”
One clue in solving the genetic mystery may come from women. As the runaway winners of the longevity marathon, women may harbour age-protective genes on the X sex chromosome, of which women have two, and men only one. Another theory posits that women are often iron deficient due to menstruation, but because iron contributes to the development of DNA-damaging oxygen-free radicals, the cells of men age more rapidly.
The study has also found women who have children after the age of 35 or 40 are four times more likely to live to 100 than women who do not. Canada’s Super Seniors Study also discovered exceptional longevity in women was twice as likely if they had children at 40 and older. But BrooksWilson stressed this association does not necessarily suggest having a baby, or having a baby later in life, will allow a woman to live longer. Rather, she says, prolonged fertility could simply be an outward sign of a successfully aging biology – something women who do not bear children may also have.
Similarly, Perls suspects it is not so much the act of having children late in life that confers a longevity advantage, but that the ability to do so may reflect a slower aging rate of a woman’s reproductive system – which hints at the existence of genetic variants that may be helping to slow the aging of the body as a whole.