Women face a significant loss of grey matter in the brain after menopause, which may explain why they are more likely to suffer dementia than men, a new study suggests.
Researchers looked at 124,780 women to examine the effects of menopause on the brain and whether hormone replacement therapy (HRT) can prevent cognitive decline.
Among post-menopausal women, they found significant reductions in grey brain matter, which is vital for mental functions, memory, emotions, and movement.
Correspondingly, the worst-affected parts of the brain were the ones governing these functions – the hippocampus, the entorhinal cortex, and the anterior cingulate cortex.
Study co-author, Barbara Sahakian of the University of Cambridge, said: “The brain regions where we saw these differences are ones that tend to be affected by Alzheimer’s disease.
“Menopause could make these women vulnerable further down the line. While not the whole story, it may help explain why we see almost twice as many cases of dementia in women than in men.”
Women account for around two-thirds of people living with Alzheimer’s disease in the UK, according to Michelle Dyson, chief executive of the Alzheimer’s Society.
“And while we still don’t fully understand why they are more susceptible than men, it is thought that hormones may play a role,” she said.
“This large study adds to evidence showing how menopause impacts the brain, including physical changes such as loss of brain volume.
“But without long-term participant tracking, to check if they later develop dementia, we cannot be sure that these brain changes associated with menopause also increase dementia risk.”
The impact of the menopause on cognition – including thinking, attention, language, learning, and memory skills – is already documented.
To examine the role played by hormones, researchers examined both pre and post-menopausal women, with the latter group subdivided into women who had used HRT and those who had never used it.
Participants answered questions about topics like sleep and whether they suffered depression and anxiety, and some took part in cognitive tests to check their memory and reaction times
Roughly 11,000 women also underwent magnetic resonance imaging (MRI) scans, allowing experts to look at their brain structure.
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Researchers found post-menopausal women who were not on HRT had slower reaction times than those who were, or those who had not yet reached the menopause.
The study also revealed that post-menopausal women were more likely to suffer from insomnia, getting less sleep overall and feeling tired.
Those on HRT reported feeling the most tired of all three groups, despite getting the same amount of sleep as those who were not.
But all post-menopausal women, whether on HRT or not, said they were more tired than women who had not gone through it.
There was no significant difference between the three groups when it came to performance on memory tasks, however.
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Co-author Katharina Zuhlsdorff, also of the University of Cambridge, said HRT appeared to have a slightly beneficial effect.
She said: “As we age, our reaction times tend to get slower – it’s just a part of the natural ageing process and it happens to both women and men.
“You can imagine being asked a question at a quiz – while you might still arrive at the correct answer as your younger self, younger people would no doubt get there much faster.
“Menopause seems to accelerate this process, but HRT appears to put the brakes on, slowing the ageing process slightly.”
Her colleague and co-author Christelle Langley said: “Most women will go through menopause, and it can be a life-changing event, whether they take HRT or not.
“A healthy lifestyle – exercising, keeping active and eating a healthy diet, for example – is particularly important during this period to help mitigate some of its effects.”
Ms Dyson echoed her advice.
She said: “There are steps that women – and men – can take today to reduce their risk of dementia, and these include regular exercise, not smoking and reducing alcohol consumption.
“If you’re worried about yourself or a loved one, Alzheimer’s Society’s dementia symptoms checklist is a helpful first step in starting a conversation with your GP.”
