Thomas Perls, M.D., a professor of medicine at Boston Medical Center who conducted the research, said that the news does not mean women should delay having children until they are older in order to boost their chances of living a longer life. Instead, a woman's age at her last childbirth is an indication of her longevity.
"The age at last childbirth can be a rate of aging indicator. 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.
Women's longevity by the numbers
Perls studied data from the Long Life Family Study (LLFS), which houses data from 551 families. His team noted the ages of 462 women and when they had their last child, then looked at how long the women lived.
Women who had their last child after the age of 33 years old had twice the odds of living to 95 years or older compared to those that gave birth for the last time at the age of 29. The study was published in Menopause: The Journal of the North American Menopause Society.
Women are genetic leaders
Perls said the study shows that women are likely the drivers of genetic variants that slow aging, which boost longevity.
"If a woman has those 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," said Perls. "This possibility may be a clue as to why 85 percent of women live to 100 or more years while only 15 percent of men do."
Older mothers have advantages
Perls said that women who can naturally give birth over the age of 33 may be criticized for having children at an "older" age, but their exceptional health is likely to be able to keep up with kids — even as the children get older.
Even in their 60s, these women will probably function as well as women in their 40s, Perl said. "They'll be very fit and healthy grandmothers and great grandmothers."
They also are likely healthier overall, Perl added. They probably are not obese and don't have conditions such as diabetes or anorexia, and they probably work out regularly and eat well.
Isn't it healthier to have fewer periods?
Upon hearing about this whole link between the reproductive system and longevity, you may wonder what happened to the notion that having fewer periods is healthier. Doesn't that lead to longevity? Perls says "no."
"Women having periods is a really good thing," he said. Women who menstruate are relatively iron deficient, and iron plays a huge role in our cells' ability to produce free radicals that can cause cell damage. Having a decreased amount of iron can be an advantage leading to slower aging. (This is probably why red meat is linked to poor health, he said.)
The other side
Serena Chen, M.D., the director of the Division of Reproductive Endocrinology in the Department of Obstetrics and Gynecology at Saint Barnabas Medical Center in New Jersey, weighed in on the reports of the study.
She said that if the study population was unselected, then most of the women likely did not have a history of infertility. In that case, it wouldn't be surprising to find that a fertile population would also be a relatively healthy population. "Older women that are healthier are more likely to be fertile," she said, adding that the prevalence of health issues in infertile women tends to be higher.
Chen added that it is possible that there is a significant psychological benefit to having children. She said that pregnancy lowers the risk for endometriosis, ovarian and endometrial cancer and fibroids.
Longevity goes beyond luck
In short, the genes that signal a healthy reproductive system are "probably" the same genes that help people age slowly, he said. The affiliations between longevity, reproductive health and menopause are all "very tightly linked to genes."
"Women who are able to have children naturally at an older age have an increased chance of getting to very old age," he said. "If you take very good care of yourself, I think the average person can get to around 90."