Study finds brain fog rises in perimenopause, but cognition holds steady

A study of 14,234 women aged 45 to 55 found more brain fog and memory complaints during perimenopause, but objective cognitive performance barely moved across menopausal stages. Researchers at King’s College London’s Institute of Psychiatry, Psychology & Neuroscience split participants into premenopause, perimenopause and postmenopause groups and had them complete eight online tasks designed to test memory and reasoning.

The pattern was reassuring in one narrow sense: overall cognitive performance differed only minimally, and the self-reported sense of thinking more slowly was tied more closely to anxiety and low mood than to test scores. King’s College London said the findings support what many clinicians hear in practice, that menopause-related brain fog is a real symptom but there is no evidence it causes lasting cognitive decline.

That matters because the symptom is common. Spontaneous menopause happens at an average age of about 51, and prior estimates put reports of brain fog and related cognitive difficulties somewhere between 40% and 80% of women. The new data suggest those complaints should be taken seriously, but not automatically read as evidence of progressive cognitive loss.

A separate 2026 synthesis led by UCL pushed the point further. It found that more than two-thirds of women report memory or concentration problems during the menopause transition, that these symptoms remain poorly recognized and under-researched, and that they are not linked to an increased risk of dementia. The review pointed to hormonal changes, sleep disturbance and psychosocial stress as likely contributors.

That framing shifts the clinical question from fear to management. The UCL review highlighted sleep improvement, regular aerobic exercise, a balanced diet and cognitive behavioral therapy-based approaches as strategies that may help some women, while evidence for hormone therapy remains mixed. It is a practical reminder that the women describing “brain fog” may be dealing with a cluster of problems, not a single disease process.

Earlier work from the Japan Nurses’ Health Study in 2022 also found that complaints of reduced cognitive functioning during perimenopause were common, even if they were not always treated as core menopausal symptoms. Taken together, the research points to validation without alarm: the subjective hit is real, the test scores are largely steady, and the most useful next steps may be better sleep, better symptom care and more careful menopause counseling.