Gerontology

Bearing a Child After Forty May Mean Longer Life Span

On average, older women take longer to get pregnant and have a higher risk of conceiving a child with chromosomal abnormalities than younger mothers. So it is refreshing to hear some positive news about reproduction later in life. Women who have a child in their forties may also live longer, according to researchers at Beth Israel Deaconess Medical Center and the Division on Aging at Harvard Medical School.

 

 

 

 

 

 

 

When Thomas Perls and Ruth Fretts studied 132 women who were born in 1896, they found that those who had had a child in their forties were more likely to live longer than those who had not. They hypothesize that late menopause may be a marker for living longer.

 

Gerontologist Thomas Perls and obstetrician-gynecologist Ruth Fretts, both instructors of medicine at HMS, compared two groups of women who were born in 1896. One group consisted of 78 women who were still alive at age 100. The other consisted of 54 women who died in 1969 at age 73. They found that the women in the centenarian group were four times more likely to have had children while in their forties than those in the septuagenarian group. Since in vitro fertilization (IVF) and other fertility-enhancing interventions for older women were not available, the later-life pregnancies were only possible because of slower aging of the reproductive system, which appears to be the link to living longer.

"It is not the act of having a child that predisposes a woman to extreme longevity, but the very fact that her reproductive system is healthy and she has not yet entered menopause," says Fretts.

Later Menopause, Longer Life

The findings, published in the September 11 Nature, have significant implications for the theoretical basis of menopause and human life span. Evolutionary pressure to extend human life span may be linked to the process of prolonging the period during which women can bear children. Perls and Fretts hypothesize that as human beings began to live longer, there came a point when death during childbirth began to increase due to the greater number of older--and frailer--women giving birth. At the age when the risk of childbirth outweighed the benefits, the forces of natural selection favored women who became infertile through menopause. If menopause evolved as a protective feature to safeguard women from the hazards of giving birth, it could be expected to occur later in slowly aging women. Therefore, the ability to have children later in life may be a marker for slower aging and longer life.

"Although menopause still occurs, the genes that allowed a woman to age more slowly may continue to exert their influence," says Perls. These observations in humans concur with experiments in fruit flies, in which the insects' ability to produce eggs later in life was linked to greater life expectancy.

Recent studies have shown that women who have estrogen-replacement therapy after menopause are less likely to develop Alzheimer's and heart disease. The same may be true for women who go through menopause later in life and therefore have a prolonged exposure to estrogen. By avoiding or at least delaying diseases associated with aging that can cause premature death, such as Alzheimer's, heart disease, and stroke, these slowly aging women live longer.

Perls, Fretts, and their colleagues will next look for connections between the genes that regulate reproductive health in aging women and the genes that regulate the pace of aging and susceptibility to age-related diseases.

--Peta Gillyatt