Menopausal women experience a drop in circulating estrogens (female sex hormones) that, for many, triggers hot flashes, headaches, anxiety and depression, trouble sleeping and, most upsettingly, memory lapses and difficulties completing familiar tasks.
Given this concurrent drop in estrogen and cognitive decline, many have studied the potential for hormone replacement therapy (HRT) to re-address the hormone imbalance and counteract any subsequent effects on cognition. But results have been mixed. Now, a study conducted at the University of British Columbia could shed some light on why.
Led by Liisa Galea, professor in the department of psychology and member of the Djavad Mowafaghian Centre for Brain Health, the researchers studied spatial learning and memory in female rats using a behavioural navigation task before and after HRT. These rats were split into two groups, those that had carried offspring, and those that hadn’t, and the researchers identified some key differences in the ‘mom’ and ‘non-mom’ groups.
Firstly, rats that had previously carried children performed better than those that had never given birth, and were better able to form new neural connections, suggesting better learning and memory.
However when treated with Premarin, once the most widely prescribed hormone therapy in the United States, the spatial learning and memory of rats that had never given birth improved. Meanwhile, although the differences weren’t dramatic, the treatment had the opposite effect on those that had carried offspring.
This split effect also appears to carry over to the immune system, with increased immune signalling in mothers, and decreased activity in non-mothers after HRT.
HRT, which is often prescribed to relieve menopausal symptoms such as hot flashes and headaches, is a contentious treatment. Its use has dropped dramatically since the early 2000s due to concerns over increased risks of breast cancer, heart disease and stroke, and a lack of clarity around the potential benefits and how reduced headaches and potential cognitive protection weigh up.
But these findings, suggesting that whether patients have carried children could impact how they respond to HRT, could have dramatic implications for how menopausal symptoms are treated.
“Previous research has suggested that our brains do change with pregnancy but it was assumed that it would bounce back a year after giving birth,” says Galea. “In fact, we are just beginning to understand how motherhood influences the brain – and it appears that these changes may have a lasting effect long after pregnancy.”
There is more work to be done to understand whether these results translate to humans, but the findings underscore the necessity of considering reproductive history when treating menopause, and could have wide-ranging implications for all kinds of hormonal therapies.