TOKYO // Jiroemon Kimura, who became the world's oldest man on record last week, can thank a combination of luck early in life and, later, good genes, for surviving seven decades longer than most of his peers.
Mr Kimura, a former postman who is 115 years and 258 days old and still greets visitors with a warm smile, dodged childhood killers such as tuberculosis and pneumonia that kept life expectancy in Japan down to 44 years around the time he was born in 1897.
As an adult living in the town of Tango, he had no major illnesses, his granddaughter-in-law Eiko Kimura said. He followed sumo wrestling on television and read two newspapers a day until the last few years.
As Mr Kimura ages, his DNA is giving him an edge. Scientists say specific genes that protect against heart disease, cancer and other old-age ailments foster longevity. Knowing the biological mechanisms involved may provide clues to counter a rising tide of non-communicable diseases predicted to cost the global economy US$47 trillion (Dh172.49 trillion) over the next 20 years.
"Getting the right combination is like winning the lottery," said Thomas Perls, the director of the New England Centenarian Study unit at Boston University. Some of Mr Kimura's genes "are likely protective against damaging cellular processes that contribute to ageing and even protective against genetic variants that may not be good for him".
Genetic factors may account for about 30 per cent of a person's chances of living to their late 80s, with behaviour and the environment contributing the remainder, Mr Perls said. The reverse is true in people who survive to 105 years, when genetic influences become more significant.
As people age, cells accumulate potentially harmful mutations as mechanisms to repair defective DNA become less efficient, said Dario Alessi, a cell biologist at the University of Dundee in Scotland.
Mr Kimura may have no major disease-causing mutations or a superior ability to repair defective genes, he said. Scientists are making conclusions about Mr Kimura based on the medical history of the centenarian and his relatives. They haven't studied his genome.
Another cellular-ageing mechanism involves DNA sequences at the ends of chromosomes known as telomeres which help determine how often cells can divide. While telomere lengths vary from person to person at the time of birth, centenarians tend to have longer ones, said Carol Greider, a professor of molecular biology and genetics at Johns Hopkins University in Baltimore, who won a Nobel Prize in 2009 for her research.
"Every time your cell divides, the telomeres get to be a little bit shorter," Ms Greider said. "You may be born with telomeres that are fine and healthy, but those will erode over the lifespan of the individual."
Mr Kimura eclipsed the male longevity record by Christian Mortensen of California, who died on December 28, 1998, according to Guinness World Records. Mr Kimura, who also became the world's oldest person after Dina Manfredini of Iowa died last month, is among 22 Japanese listed on the world's 64 oldest people compiled by the Los Angeles-based Gerontology Research Group.
Born on April 19, 1897, the third of six children to a couple of rice and vegetable farmers, Mr Kimura married his neighbour, Yae, and helped deliver his town's mail for more than 40 years, during a period marked by malnutrition-causing food shortages.
He also spent several months in a government communication unit in Korea in 1920 during Japan's occupation.
Mr Kimura's main health challenges have been cataracts and a bout of pneumonia years ago, said Mrs Kimura, the granddaughter-in-law who cares for him in the two-storey wooden house he built in the 1960s. He has normal blood pressure and a good appetite, eating three meals a day consisting of porridge, miso soup and vegetables.
During a brief visit to his home recently, Mr Kimura said he appreciated being called on by a reporter who travelled from Tokyo to meet him. He no longer hears well and spends most of his days in bed, the granddaughter said.
Mr Kimura's motto is "eat light to live long", and says the key to his longevity is to be a healthy, small eater, Guinness World Records said on Friday in a statement in which it acknowledged Mr Kimura's status as the oldest male on record and oldest living person.
"Grandpa is positive and optimistic," Mrs Kimura said. "He becomes cheerful when he has guests. Even when he falls ill, I can tell he'll recover."
Mr Kimura, who has 14 grandchildren, 25 great-grandchildren and 13 great-great-grandchildren, had few work stresses and was always very sensible, serious and disciplined, said his nephew, Tamotsu Miyake.
Even when enjoying a drink with his brothers, he would sit straight, keep quiet and remain composed.
"He has an amazing, strong will to live," said Mr Miyake, 80. "He is strongly committed to living right and well."