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Older moms much more likely to become old ladies, study says

Medical ResearchHuman Behavior
Before women dictated their childbearing histories, evolution favored those who were fertile longest
Women who could bear a child well into her 30s may have an edge in the longevity game from the start
Justice at last for mothers who cope with menopause and an adolescent at the same time

Attention, women who were declared to be of "advanced maternal age" even as their bellies swelled with life, who chased after a toddler with more patience than vigor, and who have simultaneously navigated menopause and parented an adolescent: Late-life mothering -- if it occurred naturally at least -- doubles your odds of living to an unusually old age, according to a new study.

Compared with a woman who wrapped up her childbearing by the age of 29, a woman whose last child was born after she reached the age of 33 was roughly twice as likely to survive long enough to outlive 95% of her female peers born in the same year. Women who bore their last child between the ages of 33 and 37 had the best shot at becoming a longevity champion. They were 2.08 times as likely to live to an exceptional age as moms who had no more children after 29. Women whose last child came after the age of 37 were 1.92 times as likely to live so long.

The latest research on motherhood and survival comes from a larger study of 4,875 people from 551 families in the United States (Boston, New York and Pittsburgh) and Denmark. Between 2006 and 2008, the "Long Life Family Study," which set out to discern what factors predicted exceptional longevity, enrolled groups of siblings who had lived to exceptional ages. The offspring of that long-lived generation of participants were also drawn into the study, and spouses served as a comparison group.

The women who supplied the data for the current study had all borne at least one child. The researchers compared the childbearing histories of two groups. The first group comprised 311 women from the Long Life Family Study who had survived longer than 95% of their female peers; the comparison group was made up of 151 women who had lived to at least 70 years old, but were not in the top 5% of long-lived women.

The generation examined lived in a very different world than do women of childbearing age today, and one that more closely approximates the circumstances of childbearing since the dawn of human evolution. Contraceptives were largely unavailable, and those that were were crude and prone to failure. The current trend of delaying childbearing was not the social norm. Treatments for infertility were few and rarely effective; it would be decades before babies could be conceived through in vitro fertilization.

In these circumstances, for women who were sexually active and healthy enough to become pregnant and sustain a pregnancy, babies generally came along.

So what, you ask, links the length of a woman's childbearing years and her likelihood of becoming the oldest of old ladies? What doesn't kill women makes them stronger? The kids need mom to stick around to make just one more sandwich, to drive her grandchildren to the mall, or to dispense one more bit of advice?

Maybe all of those things, suggest the authors of the study, which was published in Menopause, the journal of the North American Menopause Society. The latest research confirms and extends the findings of several other studies. Collectively, their findings suggest that robust women -- those likely to live longest -- may first manifest their good health by remaining fertile for several decades.

The research also points to some evolutionary advantage enjoyed by women capable of conceiving and bearing children for longer stretches. In turn, her longevity after her childbearing years are over confers some evolutionary benefit to her offspring and their children, since she is available longer to supplement her grandchildren's care.

The children and grandchildren of a women who reproduces late and lives long reap the benefits of her hardiness, according to this theory. Twin studies suggest that genes explain about 20% of an individual's likelihood of living into his or her 80s, and environmental factors -- including nutrition, predators, toxins and protective elders -- explain the rest. A long-lived grandma supplies larger broods, good genes and better care. She practically creates the village that ensures her longevity genes will be passed on.

Yup, I'm an older mother! Follow my coverage of women's health at  @LATMelissaHealy.

Copyright © 2014, Los Angeles Times
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