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.

Kimura, a former postman who is 115 years and 250-plus days old, dodged childhood killers such as tuberculosis and pneumonia that kept life expectancy in Japan to 44 years when he was born in 1897. As an adult living in the town of Tango, he followed sumo wrestling on television and read two newspapers a day until the past few years, said his granddaughter-in-law, Eiko Kimura.

As 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 noncommunicable diseases predicted to cost the global economy $47 trillion over the next 20 years.

"Getting the right combination is like winning the lottery," said Thomas Perls 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 percent of a person's chances of living to their late 80s, with behavior and the environment contributing the rest, Perls said. The reverse is true in people who survive to 105 years, when genetic influences become more significant, he said.

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As people age, cells accumulate potentially harmful mutations and mechanisms to repair defective DNA become less efficient, said Dario Alessi, a cell biologist at the University of Dundee, Scotland. Kimura may have no major disease-causing mutations or a superior ability to repair defective genes, he said.

Kimura's parents died at 78 and 65, but four of his five siblings lived to be more than 90 and his youngest brother, Tetsuo, died at 100, nephew Tamotsu Miyake said.