For women, being able to have children naturally later in life may be a sign that they will live an unusually long time, according to new research.
The link between the ability to give birth at older ages and longevity may be explained by genetic traits that facilitate both, the researchers said.
In the study, the researchers looked at 462 women, including 311 women who had lived to exceptionally old ages, and found that women who gave birth to their last child after age 33 were twice as likely to live to at least age 95, compared with women who had their last child by age 29.
"Of course, this does not mean women should wait to have children at older ages in order to improve their own chances of living longer," said study researcher Dr. Thomas Perls, of Boston University Medical Center. [Extending Life: 7 Ways to Live Past 100]
Instead, the findings may mean that the ability to give birth at older ages is a sign of slower aging.
"The natural ability to have a child at an older age likely indicates that a woman's reproductive system is aging slowly, and therefore so is the rest of her body," Perls said in a statement.
The researchers also found that having more than three children tempered the link between increased maternal age and survival to old ages. In other words, having too many children might work against the genetic advantages older moms may have.
The data for the study came from a larger social and genetic investigation of 550 families with members who have lived to exceptionally old ages in the United States and Denmark. In the study, the researchers defined exceptional survival as living longer than 95 percent of all people.
The new findings, published June 23 in the journal Menopause, are in line with those of a previous study by the same researchers, which found that women who gave birth to a child after age 40 were four times more likely to live to age 100 than women who gave birth to their last child at a younger age.
Previous studies have suggested that about 80 percent of the variation in people's survival to the mid 80s may be due to environmental factors such as lifestyle, whereas the remaining 20 percent may be due to genetics. The new findings suggest giving birth at a later age may be one driving force for passing on genes that contribute to living longer, the researchers said.
"If a woman has those [genetic] variants, she is able to reproduce and bear children for a longer period of time, increasing her chances of passing down those genes to the next generation," Perls said.