TUESDAY, Dec. 30, 2025 (HealthDay News) -- There is no evidence that menopause hormone therapy (MHT) use is associated with the risk for dementia in postmenopausal women, according to a study published online Dec. 22 in The Lancet Healthy Longevity.Melissa Melville, from University College London, and colleagues conducted a systematic review to examine whether MHT versus no MHT affects the risk for mild cognitive impairment (MCI) or dementia in perimenopausal or postmenopausal women, including those with premature ovarian insufficiency or early menopause. Ten studies (one randomized controlled trial and nine observational studies), with 1,016,055 participants were included.The certainty of evidence varied from moderate to very low in the included studies. The researchers found that none of the studies examined testosterone or use in premature ovarian insufficiency. There was no significant association between MHT and MCI or dementia risk. No significant effects were seen in subgroup analyses by timing, duration, or type of MHT."To cut through the noise, we reviewed the most rigorous research there is on the subject and found that menopause hormone therapy does not appear to impact dementia risk either positively or negatively," senior author Aimee Spector, Ph.D., also from University College London, said in a statement. "This review will help to inform the upcoming WHO [World Health Organization] guidelines on reducing the risk of cognitive decline and dementia, which are expected to be released in 2026."Abstract/Full Text.Sign up for our weekly HealthDay newsletter