2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
Norwegian scientists have found that on MRI, the brains of women who have given birth, on average, look younger than those of nulliparous women. They came to this conclusion after studying brain scans of more than 12 thousand women. The difference was small - only a few months - but this was enough for the neural network to determine whether a woman had given birth or not, by how her biological MRI age and chronological age correlated. The work was published in the journal Proceedings of the National Academy of Sciences.
During pregnancy, the woman's body adapts to the needs of the fetus - including saving on brain work. During this period, both in humans and in other mammals, inhibited neurogenesis and a decrease in brain volume are found. After childbirth, neurogenesis increases and the brain structures return to their original state. It can be assumed that these changes do not pass without leaving a trace and affect the further work of the brain, including the rate of aging.
Ann-Marie de Lange and her colleagues at the Universities of Oslo and Oxford have done a great job looking for signs of pregnancy in the brain. They collected MRI scans from 12,021 women from the UK Biobank database and taught the neural network to determine the biological age of the brain. By biological age, here we should understand not a calendar age, but a statistical one: first, the main signs in the structure of the brain, characteristic for different ages, are identified, and then MRI scans of each individual person are compared with his average peers.
The researchers then compared the difference between the biological and chronological age of the brain and the number of children a woman has. They found that the neural network can reliably distinguish women who have given birth from childless ones: the former have brains on average 0.4 years younger than "according to their passport." Moreover, this difference depended on the number of children: it was 0.4 for women with one child, 0.5 - with two children, 0.75 - with three, and so on.
To verify that no other factors can influence their results, the study authors again turned to data from the UK Biobank. They studied the genomes of another 271,312 women and built a polygenic risk assessment model for the number of children: that is, they determined a set of genes that allow them to predict with varying accuracy how many times their carrier will give birth. The scientists then estimated the genetic risk for their original sample of women and excluded its impact in their calculations. However, the model continued to predict brain age regardless of genetic factors.
Exactly how pregnancy and childbirth affect subsequent brain aging is still unclear. The study of Norwegian scientists turned out to be rather observational; it is impossible to draw any conclusions about the reasons for the differences between giving birth and childless women on its basis. The authors of the work put forward several assumptions. Perhaps, for example, it is a matter of softening the immune response: during pregnancy, the mother's body has to regulate the activity of immune cells so as not to harm the fetus. Or, the effect of fetal stem cells, which settle in the maternal bloodstream and red bone marrow, may be manifested. Or maybe this is a consequence of changes in the hormonal background during pregnancy and childbirth.
However, the researchers note that the anti-aging effect gradually decreases depending on the number of children: after the 5th child, the differences become less pronounced. Scientists have noticed a similar trend in related areas: for example, after the 5th child, women have an increased risk of developing Alzheimer's disease, and the minimum mortality rate is in those who have three or four children.
Gerontologists learned how to determine the age of the brain using neural networks several years ago. Since then, for example, they have found that a woman's brain is, on average, 3-4 years younger than a man's.