Women who give birth in their 40s and 50s tend to live longer — and their brothers do, too. These new sibling findings from the University of Utah suggest that late-in-life fertility is proof of a genetic makeup that increases longevity.

The fertility-longevity link, already suggested in earlier studies of women, was expanded by researchers who studied the records of Utah Mormon pioneers and Quebec Catholics, all of whom lived before the advent of modern contraception and in-vitro fertilization.

The researchers found that women who gave birth at age 45 or older were 14 percent to 17 percent less likely to die any year after age 50 than women who had not given birth after age 40. Those findings confirmed earlier studies, but those studies left this question unanswered: Did the late-fertility women live longer because of genes they inherited or because of social and environmental factors such as good nutrition or healthy living?

That question led the researchers to study the records of more than 11,000 Utah pioneer men and more than 6,000 Quebec men, each of whom had at least one sister who lived to age 50 or older. The result: The brothers were 20 percent to 22 percent less likely to die after age 50 than brothers who had no "later fertile" sisters.

The researchers also looked at the longevity of the brothers' wives and found that they did not live longer — suggesting that genes, rather than environmental or social factors, may explain the longevity boost for the brothers.

"There is probably some biological factor that keeps your vital organs working longer," reducing the rate of aging not only in the ovaries but the heart, liver and brain, said Ken R. Smith, U. professor of family and consumer studies and the study's lead author. The findings do not suggest that women should have a baby at 49 so they can live longer, Smith added.

The study, published online Monday and in the June 10 print issue of the "Journal of Gerontology: Biological Sciences," was conducted by Smith, along with Richard Cawthon, research associate professor of human genetics, and demographer Geraldine Mineau, director of population sciences at the Huntsman Cancer Institute. Other co-authors are demographers from the University of Western Ontario and the University of Montreal.

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