The social and economic implications of dementia on the society will be greatest in women because of their longer life expectancy and elevated risk for dementia compared to men. The emphasis on the management of this epidemic is shifting from early diagnosis and treatment to the prevention of cognitive impairment and dementia. Neuroprotective effects of estrogens offer the possibility of preventing or delaying cognitive decline and dementia in postmenopausal women. However, it is unclear whether or not estrogen can preserve neurological function and decrease the risk of dementia when administered early in menopause defined as the "critical window". The Kronos Early Estrogen Prevention Study (KEEPS) was a nationwide study of menopausal hormone therapy in newly postmenopausal women. Women who participated in KEEPS at the Mayo Clinic are our target population. Our objective is to assess the long-term risks and benefits of menopausal hormone therapy on Alzheimer's disease cerebrovascular disease, cognitive and mood health in women who were treated with menopausal hormone therapies compared to placebo within 36 months of their last menses; thought to be "critical window" for menopausal hormone therapy. There is a great need to clarify both risk and protective exposures in midlife. Follow-up evaluation of this group of women 12 years after they started menopausal hormone therapies provides a singular opportunity to clarify the long-term effects of menopausal hormone therapies on cognitive health. For women considering menopausal hormone therapy, the findings can provide critical insights, guiding their healthcare decisions.