Genes account for most differences in human lifespan, study finds

A paper published Thursday in Science reports that genes largely determine how long people can live, researchers led by Uri Alon of the Weizmann Institute concluded after analyzing twin and centenarian sibling data from Sweden, Denmark and the United States. The team drew on three sets of Swedish twins, including a set reared apart, compared results with Danish twins born between 1870 and 1900, and examined 2,092 siblings of 444 Americans who lived to be over 100.

Their stated goal was to separate extrinsic factors such as infections or accidents from intrinsic genetic effects on aging. Using statistical and mathematical models to eliminate causes of death not associated with aging, the authors estimated that genes account for more than 50 percent of differences in life spans in a population, compared with earlier research that suggested 25 percent or less.

They report that cancer was least likely to be affected by genetics and dementia most likely. Dr. Alon and colleagues did not dismiss lifestyle: they calculated that healthy or unhealthy habits can add or subtract about five years from a life span determined by genetic "luck of the draw." Dr.

Thomas Perls, whose Boston University centenarian data were used, said, "If you are trying to gauge your own chances of getting to 100, I would say look at the longevity in your family," and cited observational studies showing larger effects of healthy habits for midlife adults. Experts offered mixed reactions.

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