DNA lottery for long life genes
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.
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 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 in an interview.
He followed sumo wrestling on television and read two newspapers a day until the last few years, she said.
As Kimura ages, his DNA is giving him an edge. Scientists said 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 over the next 20 years.
"Getting the right combination is like winning the lottery," said Thomas Perls, director of the New England Centenarian Study at Boston University.
Some of Kimura's genes "are likely protective against damaging cellular processes that contribute to aging 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, according to Perls.
The reverse is true in people who survive to 105 years, when genetic influences become more significant, he said.
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.
Kimura may have no major disease-causing mutations or a superior ability to repair defective genes, he said.
Scientists are making conclusions about Kimura based on the medical history of the centenarian and his relatives; they haven't studied his genome.
Another cellular aging 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, 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," Greider said in an interview.
"You may be born with telomeres that are fine and healthy, but those will erode over the lifespan of the individual."
Those born with the shortest telomeres tend to suffer at higher rates from age-related degenerative diseases, she said, adding that Kimura may have long telomeres.
Though Kimura's parents died at ages 78 and 65, four of his five siblings lived to be more than 90 years old and his youngest brother, Tetsuo, died at 100, nephew Tamotsu Miyake said.
Kimura has defied the odds against his gender as well. Men make up only 15 per cent of centenarians, according to Boston University's Perls.
Genes and hormones beneficial for aging may differ between the sexes and work better in women, giving them a longevity advantage, said Nir Barzilai, director of the Institute for Aging Research at Albert Einstein College of Medicine at Yeshiva University in New York.
Kimura eclipsed the male longevity record by Christian Mortensen of California, who died on December 28, 1998, according to Guinness World Records.
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, Kimura married his neighbor, 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.
Kimura's main health challenges have been cataracts and a bout of pneumonia years ago, said Eiko 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 of porridge, miso soup and vegetables.
During a brief visit to his home recently, Kimura said he appreciated being called on by a reporter travelling to see him from Tokyo. He no longer hears well and spends most of his days in bed, Eiko said.
Kimura's motto is "eat light to live long," and said the key to his longevity is to be a healthy, small eater, Guinness World Records said in a December 28 statement in which it acknowledged his status as the oldest male on record and oldest living person.
"Grandpa is positive and optimistic," Eiko said.
"He becomes cheerful when he has guests. Even when he falls ill, I can tell he'll recover."
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, his nephew Miyake said.
Even when enjoying a drink with his brothers, he would sit straight, keep quiet and remain composed, he said.
"He has an amazing strong will to live," said Miyake, 80, in an interview.
"He is strongly committed to living right and well."
People who survive at least 100 years tend to be lean and not have diabetes or diseased arteries, according to Nobuyoshi Hirose, director of geriatric medicine at Keio University in Tokyo, who has studied Kimura and at least 500 other Japanese centenarians.
Female centenarians have twice the level of the hormone adiponectin than younger women, Hirose and colleagues found in a study published in 2006.
The hormone is secreted by fat cells that regulates the metabolism of lipids and glucose, and influences the body's response to insulin.
Typically centenarians are more open and optimistic about life, Hirose observed.
The women tend to be more conscientious and extroverted, while the men are less likely to be neurotic than non-centenarians, according to his research, published in the journal Age in 2006.
Japan, with the world's highest proportion of elderly and most centenarians, had 51,376 people older than 100 years as of September, 7.6 per cent more than a year earlier, the health ministry said.
The nation has 40 centenarians per 100,000 people, compared with 25 per 100,000 people in the US, according to the Okinawa Centenarian Study.
Since Kimura's birth, life expectancy has been extended by 39 years to become the world's longest.
Babies born in Japan today can expect to reach 83 years. Infant mortality now stands at 2.3 deaths per 1000 births, compared with 155 per 1000 when Kimura was born, according to the National Institute of Population and Social Security Research.
The oldest person ever to have lived is the late Jeanne Calment of France, who survived 122 years and 164 days, according to Guinness World Records.
- WASHINGTON POST BLOOMBERG