New research suggests that menopause may be linked to a loss of grey matter in the brain, which could help explain why women face a higher risk of dementia compared to men. Scientists from the University of Cambridge analysed data from 124,780 women to explore how menopause affects the brain and whether hormone replacement therapy (HRT) might help protect against cognitive decline.Menopause May Be Linked to Changes in Brain StructureThe researchers found that menopause was associated with reduced levels of grey matter, an essential part of the brain involved in thinking, memory, emotional processing and movement. The findings also noted that this stage of life is often accompanied by anxiety, depression and sleep problems. Previous research has already shown that menopause can affect cognitive abilities such as attention, language, learning and memory.How Menopause And HRT Affect Thinking SpeedThe study revealed that women who had gone through menopause and were not using HRT had slower reaction times compared to women who were pre-menopausal or those taking HRT. However, researchers did not find meaningful differences between the groups when it came to performance on memory-based tasks.Published in the journal Psychological Medicine, the research divided participants into three groups: women who had not yet reached menopause, post-menopausal women who had never used HRT, and post-menopausal women who were taking HRT. Participants answered questions about sleep patterns, anxiety and depression, and some completed cognitive tests measuring memory and reaction time.Around 11,000 women also underwent magnetic resonance imaging (MRI) scans, allowing scientists to closely examine brain structure. On average, menopause began at age 49 among the participants, and women who started HRT typically began treatment at around the same age.Sleep, Fatigue and Mental Health ChangesThe findings showed that post-menopausal women were more likely to struggle with insomnia, get less sleep overall and feel more fatigued. Interestingly, women using HRT reported the highest levels of tiredness across all three groups, even though they slept for a similar amount of time as those not taking HRT.All post-menopausal women, regardless of whether they were using hormone therapy, reported greater fatigue compared to women who had not yet experienced menopause. Researchers also observed that this stage of life had an impact on cognitive function.Dr Katharina Zuhlsdorff, from the psychology department at the University of Cambridge, explained: “As we age, our reaction times naturally slow down. This happens to both women and men and is part of normal ageing. You might still reach the right answer to a quiz question, but younger people tend to respond faster. Our findings suggest menopause speeds up this slowing process, while HRT seems to slow it down slightly.”Brain Regions Linked to Memory and Emotion AffectedThe study identified significant reductions in grey matter volume among post-menopausal women. These changes were seen in the hippocampus, which plays a key role in learning and memory, the entorhinal cortex, which supports memory formation and spatial awareness, and the anterior cingulate cortex, which helps regulate attention and emotions.Menopause As A Period of Increased VulnerabilityProfessor Barbara Sahakian, the senior author of the study from the department of psychiatry, said: “The brain areas where we observed these changes are the same regions commonly affected by Alzheimer’s disease. Menopause may make women more vulnerable later in life. While it does not explain everything, it could help clarify why dementia affects nearly twice as many women as men.”Michelle Dyson, chief executive of the Alzheimer’s Society, noted that women account for roughly two-thirds of people living with Alzheimer’s disease in the UK. “Although we do not yet fully understand why women are more affected than men, hormones are thought to play a role,” she said.“This large-scale study strengthens evidence that menopause has an impact on the brain, including physical changes such as reduced brain volume. However, without long-term follow-up to see whether participants later develop dementia, we cannot be certain that these menopause-related brain changes directly increase dementia risk.“There are steps people can take today to lower their dementia risk, including regular exercise, avoiding smoking and cutting back on alcohol. Anyone concerned about themselves or a loved one can use the Alzheimer’s Society dementia symptoms checklist as a starting point before speaking to a GP.”The research also found that women taking HRT were more likely to report mental health challenges. However, the analysis suggested these women already had poorer psychological wellbeing before starting hormone treatment.Dr Christelle Langley, from the psychiatry department, said: “Menopause is something most women will experience, and it can be a major life change whether or not HRT is used. During this time, healthy habits such as staying active, exercising regularly and eating a balanced diet become especially important to help reduce some of its effects.”Dr Louise Newson, a GP and women’s hormone specialist, added: “Many women notice changes in memory and concentration around menopause. This study suggests these symptoms may have a biological explanation rather than being brushed off as stress or ageing, highlighting menopause as a key window for protecting brain health and providing personalised care.”