Mothers may not be joking when they say their children give them gray hair.
In a recent Yale co-authored study, researchers studied five villages in southern Poland to find links between reproduction and decreased lifespan. The study examined 112 postmenopausal females with different ranges of reproductive investment, measured by how many times a woman has been pregnant. The results illustrated the relationship between high fertility and high oxidative stress — the imbalance between the accumulating natural, but toxic byproducts of metabolism and the body’s inability to detoxify and repair the damage . According to the study, compared to those who had three pregnancies or less, women who underwent at least four pregnancies had 20 percent higher levels of 8-OHdG, a product of oxidative stress from DNA, and 60 percent higher levels of Cu-Zn SOD, an oxidative stress marker and a known contributor to aging.
“This is a very important finding in terms of public health,” said Grazyna Jasienska, study co-author and lead researcher and assistant professor at Jagiellonian University. “This tells us that women with a high level of reproduction investment may have need for special health programs or prevention disease programs.”
Jasienska said her motivation for the research came from an interest in combining public health and evolutionary biology. Anna Ziomkiewicz, study co-author and senior researcher at the Polish Academy of Sciences, noted that in previous studies conducted on female animals, researchers found a decrease in birds’ survival when scientists added eggs to their nests. The study authors said they wanted to understand if these trade-offs were evident in humans as well.
Ziomkiewicz explained that their study participants’ population had a high fertility rate, as they had not used contraceptives until recently. Jasienska added that there was a large diversity in childbirth numbers among study subjects, with some households having as many as 16 children.
The researchers said the next step will be to look into other populations for similar relationships. Jasienska said they are not sure if the results are universal for the female population or only present in some populations.
“We want to see if responses to childbirth differ between populations,” said Richard Bribiescas, study co-author and professor of anthropology and ecology and evolutionary biology. “We’re doing this in the tropics with a hunter-gatherer population right now, and we want to see how robust those results are.”
Ziomkiewicz said there have been experiments exploring potential treatments, such as doses of antioxidants, to reverse the effects of oxidative stress, but with “ambiguous effects” — some studies indicated decreased birth weights of babies. She added that it was best to encourage women to have a healthy lifestyle as a preventative measure for accelerated aging.
This study was supported by the Fulbright Commission, Polish National Science Centre, Polish Ministry of Sciences and Higher Education, Yale University and Salus Publica Foundation.