A new Lancet paper proposes a formal definition to drive research and treatment.
Scientists have moved to formally define menopause-related brain fog, calling for clinical studies to investigate its causes and develop targeted treatments for a symptom that affects many women but remains poorly understood.
Researchers from Monash University, the University of Melbourne and University College London outlined the definition in a paper published in The Lancet Obstetrics, Gynaecology & Women’s Health, arguing that clearer clinical recognition was essential to advance research and improve care.
The proposed definition characterises menopause brain fog as self-reported cognitive impairment that can significantly affect quality of life despite the absence of measurable cognitive decline on objective testing.
Symptoms commonly include forgetfulness, reduced attention and difficulty concentrating.
Cross-sectional studies suggested that between about a quarter and more than 90% of women report memory-related symptoms during perimenopause, the researchers reported, and many also experience concentration difficulties.
Evidence indicated that these symptoms often peak during the transition to menopause and may lessen afterwards.
While most objective cognitive tests showed performance remaining within normal ranges, some studies have identified subtle associations between subjective cognitive complaints and measures of learning efficiency, attention and processing speed.
The researchers noted that the causes were likely multifactorial, involving hormonal changes alongside factors such as sleep disturbance, mood symptoms, stress and midlife health conditions.
However, they said a lack of a clinical framework had slowed progress in understanding why the symptom occurs and how it might be treated.
Hormonal changes during menopause are thought to play a central role, but the underlying mechanisms remain unclear.
Lead researcher, Associate Professor Caroline Gurvich, a clinical neuropsychologist and researcher from Monash’s HER Centre, said establishing a definition was an important step toward recognising brain fog as a legitimate clinical feature of menopause and enabling it to be studied in trials.
“There’s a lot of pressure to use objective measures of cognitive decline, like a memory test, for example, in a clinical trial, but the key symptom of brain fog is a subjective experience,” she said.
“So having a definition that acknowledges the key cognitive symptom is critical.
“This is not without precedent – we already use subjective or self-report measures for depression, anxiety and other mental health conditions with great success.”
A formal definition could also help validate women’s experiences while reassuring patients that any measurable cognitive decline was typically subtle.
Professor Gurvich said the symptom reflected reduced efficiency rather than loss of cognitive capacity, although many women feared it signalled more serious deterioration.
“For many women, the perception they are losing capacity is what drives them to stop work or lose the confidence to live fulfilling lives during and after menopause,” she said.
“I hear all the time from women who have gone through menopause that validation would have made a significant difference to their resilience and the approach they took to living with menopause.”
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Co-author Professor Martha Hickey, from the University of Melbourne and Royal Women’s Hospital, said the study highlighted gaps in the evidence base.
“Our analysis of the best available research shows that many women experience some degree of cognitive symptoms, such as brain fog, during the menopause transition,” Professor Hickey said.
“But there’s a lack of long-term data, which means that there’s a gap in our knowledge about how the brain fog symptom develops and changes from perimenopause to after menopause ends.”
The researchers said clinical trials were particularly needed to determine whether hormonal therapies, psychological interventions or lifestyle approaches, such as exercise, sleep improvement and cardiovascular risk reduction, could reduce cognitive symptoms.
In the meantime, clinicians were encouraged to acknowledge and validate women’s experiences and provide education about potential contributing factors and strategies to support overall cognitive health.
“Clinicians have an important role in validating women’s experiences of cognitive symptoms during menopause, managing and providing psychoeducation on potential causes, and using these encounters to consider evidence-based lifestyle modifications that can help mitigate cognitive symptoms and improve overall cognitive health,” the researchers concluded.
The Lancet Obstetrics, Gynaecology & Women’s Health, April 2026
