Women who had their last child at age 33 years or older were more likely to reach extremes of longevity, according to an analysis published online June 23 in Menopause.
Women who had their last child when they were aged 33 to 37 years were twice as likely to reach the extreme fifth percentile of longevity compared with women who had their last child before that age.
"Prolonged fertility may be a marker of slower aging," write the authors, led by Fangui Sun, PhD, from the Department of Biostatistics at Boston University in Massachusetts. Previous studies, including some on historical data in the 17th, 18th, and 19th centuries, had found that women who had their last children late in life tended to live longer and to have siblings who lived longer.
Dr. Sun and colleagues analyzed data from the Long Life Family Study, whose participants have multiple family members who have reached extremes of longevity. The population includes sets of siblings selected because of their collective longevity scores, along with their spouses and children. The families were recruited between 2006 and 2009 in Boston; Pittsburgh, Pennsylvania; New York City; and Denmark.
One hypothesis to account for the association between maternal age and longevity, write Dr. Sun and colleagues, is that women whose bodies use energy more efficiently are able to both avoid age-related diseases and have increased fertility. The authors suspect these women would also be more likely to have more children, but in this study, they found a nonsignificant association in the opposite direction: having 3 or more children decreased the likelihood of extreme longevity.
The authors note that twin studies have suggested that genetics only explain about 20% of variation in longevity but that the influence of genetics increases at older ages. In other words, environmental and behavioral factors may influence a person's likelihood of living to their mid-80s, but in the extremes of old age, genetics play more of a role. They suggest that studying the genetics of fertility may reveal genes that influence longevity.
The Long Life Family Study was funded by the National Institute on Aging/National Institutes of Health.
Menopause. Published online June 23, 2014.