A new study from Researchers at Penn State University finds that having the right number of children is a bit like the fairy tale “Goldilocks and the Three Bears.” There is a too little, a too much, and a just right.
Any mother can tell you that having kids makes you feel older. The research team wanted to find out if having kids makes you biologically older. The researchers are trying to learn more about why some people age faster than others. For women, pregnancy would seem like an important factor because pregnancy, birth, and breastfeeding require a tremendous amount of energy. That energy may reduce the amount of energy needed for important work like maintaining health and protecting against disease. This trade-off is called “the cost of reproduction.”
The cost of reproduction may explain why women who have given birth are more likely to die from diabetes, kidney disease, and high blood pressure than women who never had children. To learn more about how pregnancy affects aging, the research team evaluated data from the National Health and Nutrition Survey, an ongoing survey done by the CDC. The survey includes information on pregnancy and other areas of health. The team was able to gather data on pregnancies, menopause, and blood tests that measure biologic health associated with aging.
The study results are reported in the journal Scientific Reports. Over four thousand women were included the survey. The research team used biologic markers like blood sugar, blood pressure, liver function, kidney function, immune system function, inflammation, and red blood cell health to learn how the number of pregnancies affects biologic age.
The results are surprising. As expected, having more than four children increased biological age after menopause. However, having less than three children also increased biological age, even after factoring in lifestyle factors that could accelerate aging like smoking, obesity, and socioeconomic status. The “just right” spot for aging was three to four children.
The finding that having more than four children can age a woman beyond her age in years is not surprising and goes along with the cost of reproduction theory. Why women who have less than three children age faster is unknown. It may be that up to a point, pregnancy makes the body stronger. It may also be that women who are less healthy early in life, have less social support, or have other life stress tend to have less children.
The research team says the unanswered questions point to areas that require future research. Studies that try to learn more about biologic aging are important for understanding how to improve health in women and men over age 60, a population that is expected to keep increasing over the next 30 years. These studies may increase years of healthy aging, called a person’s “health span.”