But he says the link between late motherhood and longevity "could be something that is not inherited. It could be good nutrition or really good living, suggesting that if you are a healthier mom you live longer."
That is why the researchers looked at the lifespan of the brothers of women who had babies late, and of those brothers' wives. The wives are not blood relatives, so genetic factors shared by sisters and brothers wouldn't be the same in the brothers' wives.
Smith says the study focused on the longevity of brothers rather than sisters of late-fertile women because "men's own reproductive history doesn't get in the way of assessing the role of their female relatives' fertility."
The study focused on the two pioneer groups not only because of the quality of the data but because of the absence of modern birth control and an unfavorable attitude toward natural family planning methods by Mormons and Catholics. Also, a link between late fertility and lifespan is easier to observe in large families with more sisters.
Since all of those studied are now dead, the researchers could look at the full length of their fertile periods and lives. "Not many data sets could do this," Smith says.
The researchers controlled for various factors that could skew the results. For example, they excluded any individuals who did not live to at least 50 because a husband's death at a younger age would influence his wife's child-bearing.
Late Babies Linked to Longer Life for Moms and Blood Uncles
|Contact: Lee Siegel|
University of Utah