During menopause, brain changes surprisingly take a break

Major hormonal changes during pregnancy and the first menstrual period, known as menarche, are reflected in the brain. But during menopause, brain changes seem to take a break. In a study of more than 1,000 female brains, brain gray matter volume decreased at menarche and again during pregnancy, changes that are permanent and distinct from age-related decline.

There was no change during menopause, scientists report September 8 in Nature Communications. The results are surprising, but hint at how hormone ebbs and flows over the lifetime are reflected in brain structure. In addition to age-related alterations, the brain reacts to hormone changes, particularly the extreme hormonal shifts in pregnancy and puberty.

During pregnancy, overall brain volume will shrink by about 4 percent, something van ’t Hof describes as “neural fine-tuning.” The brain isn’t losing function; it is remodeling, preparing for parenthood. Few studies have examined brain changes across menopause. van ’t Hof and her colleagues analyzed data from structural MRI studies at Leiden University and the UK Biobank. The researchers ended up with a set of 1,095 scans, including adolescent brains pre- and post-menarche, and adult brains pre- and post-pregnancy and pre- and post-menopause, compared with hormonally stable controls.

As expected, the scientists saw gray matter reductions in the cortex — the outer layer of the brain — associated with pregnancy and menarche. But they observed no decreases in gray matter during menopause. In fact, while there were expected age-related decreases in gray matter volume in brains before and after menopause, during menopause, that usual decrease ceased.

Brain scans at puberty (before, during and after the start of menarche) and pregnancy (never pregnant, first pregnancy, second pregnancy) show decreases in gray matter by about 0.1 percent. Hormone surges during those life stages are linked to the brain changes. Menopause, however, is characterized by a decrease in circulating hormones.

Brain scans reveal that at menopause (before, during and after), the normal slight decreases in gray matter cease, and gray matter doesn’t appear to change at all. For both menarche and pregnancy, surges of hormones are associated with decreases in gray matter. So, it might make sense, in theory, that the hormonal decreases of menopause could do the opposite — boost gray matter.