Postmenopausal estrogen-based hormone therapy lasting longer than 10 years was associated with a decreased risk of Alzheimer disease in a large study carried out at the University of Eastern Finland.
"The protective effect of hormone therapy may depend on its timing: it may have cognitive benefits if initiated at the time of menopause when neurons are still healthy and responsive," says Bushra Imtiaz MD MPH, who presented the results in her doctoral thesis.
The study explored the association between postmenopausal hormone replacement therapy, Alzheimer disease, dementia, and cognition in 2 nation-wide case-control studies and 2 longitudinal cohort studies. The largest study comprised approximately 230,000 Finnish women and the follow-up time in different studies was up to 20 years.
Alzheimer disease is the most common cause of dementia, and 2 out of 3 Alzheimer disease cases are women. One possible explanation for women's higher dementia risk is the postmenopausal depletion of sex steroid hormones estrogen and progesterone. Estrogen receptors are present throughout the body including brain areas primarily affected in Alzheimer disease. In in vitro and animal studies, estrogen has showed neuroprotective effects. However, studies on humans have yielded inconsistent results on the association between postmenopausal estrogen-based hormone replacement therapy and dementia risk.
In the present study, long-term use of hormonal replacement therapy was associated with a better performance in certain cognitive domains - global cognition and episodic memory - and a lower risk of Alzheimer disease. Short-term use was not significantly linked to dementia risk, but in one cohort, dementia risk was higher among short-term users who had started hormone therapy in the late postmenopausal period. The results were adjusted for various lifestyle, socioeconomic, and demographic variables.
"In the light of these findings, hormonal replacement therapy may have a beneficial effect on cognition if started early, around the time of menopause. The protective effect of hormonal therapy may depend on the health status of neurons at baseline and may be lost if therapy starts years after menopause," Dr Imtiaz concludes.
The study also showed that the postmenopausal removal of ovaries, uterus, or both was not significantly linked to the risk of Alzheimer disease, irrespective of the indication of surgery or hormone therapy use.
The research data was from the MEDALZ (Medication use and Alzheimer's disease), OSTPRE (Kuopio Osteoporosis Risk Factor and Prevention Study), and CAIDE (Cardiovascular Risk Factors, Aging and Dementia) studies. The newest results were published recently in Neurology and Maturitas and the earlier results in the Journal of Alzheimer's Disease.
Source: News Release
University of Eastern Finland
February 16, 2017