"The most popular hypothesis [there] is that people in the past had poor sanitation in towns, and hence a high infection load early in life," Gavrilov said. Farms were more isolated, and so farmers were less likely to contract life-limiting illnesses, he reasoned.
Not unexpectedly, overweight -- what the researchers described as a "stout" physique -- reduced a man's likelihood for very long life. In fact, slender or medium-built men were twice as likely to reach the century mark compared to stout types.
But, "surprisingly, there is not much difference between the slender and the medium body build, in terms of survival chance to 100," Gavrilov said. That runs counter to the results of animal studies that have suggested that low-calorie diets, and resultant skinniness, boosts longevity.
Other characteristics -- including marital and immigration status at 30 -- had little or no impact on longevity.
Finally, taller men were only marginally more likely to live to 100 than their shorter peers, the team found. Experts have long linked shorter adult height to the types of childhood infections that might shorten lifespan, so this finding is also a bit of a puzzle, Gavrilov said.
"We need to make a larger study and take a closer look at the links between adult height, childhood infection and longevity," he said.
He stressed that findings for women would no doubt be different, for a variety of reasons. "We need to find [similar] data for women to get the answer," Gavrilov said.
There's more on healthy aging at the U.S. National Institute on Aging.
SOURCES: Leonid Gavrilov, Ph.D., Center on Aging, University of Chicago; Arnold Mitnitski, Ph.D., associate professor, departments of medicine, mathemat
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