Yasutaro Koide, 112, receives the Guinness World Records certificate as he is formally recognised as the world's oldest man, at a nursing home in Nagoya, central Japan, on August 21, 2015 Image Credit: REUTERS/Kyodo

Known as Wall Street’s oldest stockbroker, Irving Kahn died this year at the age of 109. He was born in 1905, made his first trade in 1929 before the Great Depression hit and continued to work for years after celebrating his 100th birthday. Remarkably, Kahn and his three siblings all reached the centenarian mark (age 100) while remaining relatively alert, active and healthy.

But as incredibly age-defying as they were, none of the Kahn siblings reached supercentenarian status — 110 years and older — in what appears to be a much harder feat for the human body to accomplish. While the Census Bureau reported about 50,000 centenarians living in the United States in 2010, there are only 50 to 80 supercentenarians in the entire world.

Genes or luck?

So what does it take to live to 110 and beyond? Is it a unique genetic profile, healthy habits or simply the luck of the draw? The answer is far from simple, and probably entails all of the above to some extent. But one thing researchers agree upon: supercentenarians aren’t your average human beings.

The vast majority of us have a set of genes that will allow us to reach our late eighties and early nineties. Whether your death comes sooner or later than the next person is largely dictated by your lifestyle and environment, with harmful things such as smoking and drinking essentially fighting against your genes to lower your life span.

On the other hand, adding more-positive behaviours (eg, exercise, diet, stress management) might tack on a few years — but it won’t make you a supercentenarian.

“Healthy living, diet, exercise — that sort of stuff will benefit you, and you might lead a life longer by maybe five years,” said geneticist Stuart Kim of the Stanford School of Medicine. “But to live 30 years longer, you probably need a different genetic background.”

Reports of the world’s longest-living person, 122-year-old Jeanne Calment, all say she frequently enjoyed cigarettes and port wine. Irving Kahn’s older sister — Helen Reicher, who died just shy of her 110th birthday — smoked daily for more than 80 years. As much as we’d like to think that might give us a free pass to indulge, such stories just reinforce the theory that supercentenarians probably possess a special resistance to disease written into their genomes.

“To live to about the age of 90, 20 to 30 per cent of that is going to be genetics, and 70 to 80 per cent is going to be your health behaviours and your environment,” said Thomas Perls, a professor of medicine and geriatrics at Boston University. “If you want to live beyond 90, then I think there’s this growing genetic component that you don’t necessarily have a choice over.”

In a 2012 study published by the journal PLOS ONE, Perls and colleagues looked for genetic signatures of exceptional longevity in the genomes of 801 centenarians. No single gene stood out, but the top 281 genetic variants that were most associated with old age served as a sort of constellation of genetic markers that were strongly associated with extreme old age.

“If you inherit just the right combination of variations of those genes, then that can have a very, very strong influence on the ability to get to a very old age,” he said. “It’s like the lottery: If you get one number or two numbers, that’s not a very rare event. But to get all seven numbers, or to get all genes in the right combinations, that’s very rare.”

The average human life expectancy has increased at a rate of three months per year since 1840, with no signs of slowing down. Ageing researchers have found a delay in the onset — or even a complete absence — of age-related diseases such as diabetes and Parkinson’s disease in supercentenarians, even more so than in centenarians. Supercentenarians aren’t just living longer: they’re living healthier, too.

So what kind of genetic lottery does living a decade beyond 100 entail? Last year, Kim sequenced the whole genomes of 17 supercentenarians — the largest group yet for such an experiment — to find out.

“We had hoped that there would be some crazy mutation in there that would confer crazy-long life spans on a person,” Kim said. “Now that we looked at 17 supercentenarians, all I can say is that if [the genetic signatures] were really simple, some of the tests we did would have found them.”

Perls believes it would take 500 to 1,000 genomes to truly unlock their secrets.

— Washington Post