A critical window for hormone therapy and dementia risk?

New work on hormone therapy and dementia risk indicates that the timing of taking HRT could be vital in determining the impact on dementia. This work shows that menopausal women may benefit from appropriate use of HRT, while older women need to be more cautious. Because of the potential importance of this new research, the International Menopause Society is issuing the following statement, written for the IMS by Professor Victor Henderson (Stanford, USA).

New findings from a large US health maintenance organization examine a woman’s risk of dementia during late life based on the timing of hormone therapy use.1 Compared to women not using hormone therapy during midlife or late life, midlife-only use was associated with a significant reduction in dementia risk.1

Commenting for the IMS, Professor Victor Henderson (Stanford, California, USA) says:
“In this study, the incidence of dementia differed strikingly between women who used hormone therapy only during midlife (26% reduction in risk) and women whose hormone use occurred only later in life (48% risk increase). In both instances, comparisons were to women who did not use hormone therapy at either time. These results may help reconcile findings from the Women’s Health Initiative Memory Study (WHIMS) trial, in which the incidence of dementia was increased for hormone therapy initiated during late life,2 and observational findings that imply that hormone therapy — typically used only during midlife — is associated with reductions in Alzheimer’s disease risk.3-5 More generally, this research supports the critical window, or timing, hypothesis, according to which hormone therapy used by younger women closer to the time of menopause lowers Alzheimer risk but used by older women more remote from menopause elevates Alzheimer risk.6 Because prolonged use (midlife plus late life) in this study was not linked to reductions in dementia risk,1 these findings reinforce the need for caution if hormone use extends beyond a midlife ‘window’ but provide additional reassurance if used for approved indications during midlife.”