Does fertility have effect on aging?
Research looks at aftermath of a woman’s pregnancy, childbirth in later stages of life
Women undergo significant physical, hormonal and physiological changes during pregnancy and childbirth. Now, researchers are trying to understand how the female aging process is affected.
The research is still in its early stages involving the investigation of several biological markers of aging.
These include telomeres, or the end caps of chromosomes that have been shown to shorten as we age; epigenetics, the study of whether certain genes get turned on and off; and microchimerism, a fascinating phenomenon where cells from mom and baby go back and forth across the placenta during pregnancy, with some colonizing long-term in one or both bodies.
Some studies report pregnancy and childbirth dramatically accelerate aging in women at the cellular level. Other research, suggests motherhood and pregnancy may slow aging.
These types of contradictions are bound to be found during the early stages of research, said Dan Eisenberg, a biological anthropologist at the University of Washington. Last year, Eisenberg and his colleagues published a paper in the journal Scientific Reports, which found with each pregnancy a mother’s telomeres appear to be about four months to four years older than those of her childless peers.
Telomeres sit at the end of chromosomes, the threadlike structures that contain our genetic material. Telomeres are like the hard end of shoelaces and serve as protection for the chromosome. When telomeres get too short, cells die and stop replicating. Shorter telomeres are associated with an increased risk of cardiovascular disease, cancer, diabetes and other health conditions. Although telomeres are known to shorten in all humans with age, certain things, such as cigarette smoking, a high body mass index and major stress may accelerate the shortening process. Good sleep, regular exercise and a Mediterranean diet have been associated with longer telomeres.
Eisenberg ’s study was conducted on over 800 women in their early 20s in Cebu, Philippines. Roughly 60 per cent never had children. The remaining had given birth to one or more children.
The study also looked at the epigenetic age of women: The more pregnancies a woman went through, the “older” her epigenetic age. “These are very young women though. We don’t know if this effect persists as they get older. Maybe they just bounce back over time,” said Calen Ryan, a biological anthropologist at Northwestern University.
Paradoxically, Ryan, Eisenberg and their colleagues found that if a woman was pregnant at the time the measurements were taken, she looked epigenetically “younger” than expected. However, they did not find the same effect when they looked at telomere length.
Eisenberg is involved in a new study looking at this, known scientifically as microchimerism, in a subset of the same population of women he previously studied in the Philippines. He would also like to analyze telomere length in women before and after pregnancy, to see how it changes.
Some of the results his team is finding could be specific to the population in the Philippines, where mothers are younger and fertility rates are higher than in the U.S.
At least one study on telomere length of U.S. women has found results along the lines of what Eisenberg and Ryan found. Published in the journal Human Reproduction, the study relied on data from the National Health and Nutrition Examination Survey and looked at telomere length in nearly 2,000 U.S. women between the ages of 20 and 44. The researchers found that women who had live births had telomeres that were an average of 4.2 per cent shorter than their counterparts with no children.
This equates to around 11 years of accelerated cellular aging, said Anna Pollack, an epidemiologist at George Mason University and the lead researcher of the study.