Having a baby after age 35 may increase a woman’s cognitive abilities in middle age, according to the newest study to continue unraveling the complex interactions between women’s health and reproduction. The study was conducted by researchers from the University of Southern California and published in the Journal of the American Geriatrics Society.
“While it is not enough to suggest that women wait until after 35 years of age to close their family growth, our finding of a positive effect of later age at last pregnancy on late-life cognition is novel and substantial,” lead author Roksana Karim said.
End a little later?
Previous studies have focused mostly on the other end of women’s reproductive life, examining whether teen and other young mothers have worse health outcomes than women who wait a little longer to start their families. Overall, studies have found that women who give birth to their first child between ages 15 and 24 are less healthy in middle age than women who start having children at 25 or later.
It is unclear whether this difference in midlife health is due to pregnancy-related physiological factors, or whether it is better explained by socioeconomic factors that both lead to and stem from early pregnancy.
Rather than looking at overall health, the current study specifically measured cognitive ability. Researchers found that women who had their last child after age 35 scored higher on tests of cognition and verbal memory. The researchers said that this might make these women less likely to suffer cognitive decline later in life.
“More research is warranted to evaluate the underlying mechanism of this phenomenon and also to understand the role of age at first pregnancy,” Karim said.
The researchers also found that women who had more than one child scored higher on cognitive tests than mothers of just one.
Scientists also found that women who had their first child after age 24 scored higher on tests of reasoning and problem-solving in middle age, than did those who gave birth at a younger age.
The power of hormones
The study was correlative, and therefore could not prove any reason for the connection between age of last (or first) birth and middle-aged cognitive ability. But the researchers noted that the hormonal changes of pregnancy are known to cause striking changes to brain function.
“It has been suggested that functional brain changes induced by reproductive experiences have lifelong effects, particularly in terms of improvement in memory and learning,” the researchers wrote. “Therefore it is biologically plausible that a late pregnancy might offer protection against cognitive decline in later life.”
This hypothesis is supported by other research showing a connection between exposure to female sex hormones and later cognitive ability. For example, studies have found that women who use hormonal birth control for more than a decade show improvements in problem-solving and memory, while other studies have shown that women who hit puberty later are more likely to eventually develop Alzheimer’s disease. And animal studies have shown that improvements in memory and learning ability may start during pregnancy.
On the other hand, it is interesting to note that the younger a woman has her first child, the lower her lifetime breast cancer risk. This risk decreases even further the longer a woman breastfeeds.
The female breast develops very slowly, maintaining a large proportion of undifferentiated cells well into adulthood. These cells are believed to be more vulnerable to carcinogens and other toxins. But once a woman becomes pregnant, the breast quickly becomes fully mature to prepare for breastfeeding.
Sources for this article include: