The study confirmed a previous finding that women who have babies naturally in their 40s or 50s tend to live longer than other women.
However, it also found that their brothers live longer too, but the their wives don”t, suggesting the same genes prolong lifespan and female fertility, and may be more important than social and environmental factors.
“If you have a female relative who had children after age 45, then there may be some genetic benefit in your family that will enhance your longevity.” says the study”s lead author, demographer Ken R. Smith, a professor of family and consumer studies at the University of Utah.
The researchers examined high-quality genealogical records from the Utah Population Database at the University of Utah with its records of 1.6 million Utah Mormon pioneers and their descendants.
They also used the University of Montreal”s Program on Demographic History Research, which has records on 400,000 people who lived in heavily Catholic Quebec between 1608 and 1850.
Specifically, the study involved the records of 11,604 Utah men who were born between 1800 and 1869 and who had at least one sister who lived at least to age 50; and the records of 6,206 Quebec men who lived between 1670 and 1750, and had at least one sister who lived to 50 or older.
The researchers found that women who had “late fertility” – a birth at age 45 or older – were 14 percent to 17 percent less likely to die during any year after age 50 than women who did not deliver a child after age 40.
They also found that brothers who had at least three sisters, including at least one sister who gave birth at age 45 or later, were 20 percent to 22 percent less likely to die during any year after age 50 than brothers who had no “late fertile” sisters.
That indicates that the same genes may influence the lifespan of both sexes and women”s ability to give birth at older ages.
The brothers” wives didn”t have longer lives, suggesting any environmental or social factors that influence lifespan had only a weak influence, and that genes may explain why brothers lived longer when they had a sister who gave birth in her 40s.
The study didn”t address how much longevity is due to genetics, but scientists believe genes account for up to 25 percent of differences in longevity.
The study will be published online May 4 and in the June 10 print issue of the Journal of Gerontology: Biological Sciences.