Menopause-related brain fog as a midlife window in women's brain aging: toward ecologically valid measurement and digital phenotyping.

Cognitive complaints commonly described as "brain fog" are frequent during the menopause transition and often involve attention and memory difficulties that can affect daily functioning and quality of life. Midlife women may worry these symptoms signal early neurodegenerative disease, yet available evidence indicates that menopause-related cognitive changes are typically mild, variable, and distinct from dementia. Midlife, typically spanning approximately ages 40-60 years and encompassing the menopause transition (most commonly occurring between 45-55 years), represents a critical period for women's brain health. A major barrier to progress is that "brain fog" remains inconsistently defined and measured, limiting comparability across studies and constraining prevention-oriented strategies. In this Perspective, we propose that menopause-related brain fog represents a time-limited, clinically meaningful "measurement window" in women's brain aging trajectories, in which symptoms may be most detectable and potentially modifiable if assessed with tools that capture real-world fluctuation. We propose a pragmatic, multi-layer measurement framework that integrates (1) patient-centered symptom and functional impact profiling, (2) brief targeted cognitive assessment of vulnerable domains, and (3) ecological momentary assessment combined with passive and active digital measures using wearable and smartphone-based metrics (sleep, activity/circadian regularity, autonomic proxies, and brief repeated digital cognitive tasks). We outline validation principles, equity considerations, and reporting recommendations aligned with sex- and gender-aware research practices. By operationalizing menopause-related brain fog and linking it to feasible digital measurement strategies, aging neuroscience can better distinguish normative midlife cognitive variability from concerning trajectories, accelerate mechanistic research, and support preventive brain health interventions for women.