Mental Health Update | Hormone replacement therapy (HRT) contains female hormones (estrogen and/or progestogen) .....
....and is often used for the treatment of symptoms such as hot flashes and night sweats in women undergoing menopause.
Findings come from a large observational study that included 84,739 women from Finland.
Data on their HRT use were obtained from a nationwide register that included all HRT users from 1994. Alzheimer's disease diagnosis was performed according to internationally approved criteria while ruling out other forms of dementia or cognitive decline.
As for types of HRT, women with a uterus had to take estrogen along with a progestogen to reduce the risk of endometrial cancer, whereas women who had undergone hysterectomy could take an estrogen-alone therapy.
For women who initiated HRT before the age of 60, the use of HRT that included both estrogen and progestogen was associated with a 17% increase in risk for Alzheimer's disease compared to women who did not use HRT. For women who had undergone hysterectomy and started estrogen-alone HRT before the age of 60, there was a 9% increased risk for Alzheimer's. The increase in risk was only observed in women who took HRT in oral or patch forms for durations longer than 10 years. The exclusive use of vaginal estrogen was not associated with an increased risk for Alzheimer's.
For women who initiated HRT after the age of 60, the use of HRT (estrogen and progestogen or estrogen alone) was associated with a 15-38% increase in risk for Alzheimer's disease compared to women who did not use HRT. In this age group, the increased risk was evident after 3-5 years of HRT use.
Although these findings may be alarming, it is worth noting that the evidence is conflicting. Several previous observational studies have suggested a relationship between HRT use and decreased risk for Alzheimer's. Also, it is important to remember that an observational study like this one is not designed to prove that HRT is responsible for Alzheimer's disease—it is designed to show an association, not causation. 
In fact, two randomized controlled clinical trials (which were designed to evaluate causation) have shown that short-term HRT (2-5 years) started within a few years of the onset of menopause was neither beneficial nor harmful for cognitive health.
Together, findings from the latest study combined with previous reports are consistent with the current recommendations from the North American Menopause Society. If you are interested in using HRT, talk to your healthcare provider so you can understand the benefits and risks while choosing the type, dose, formulation, route, and duration that is most appropriate for you.
Once you start using HRT, continued discussions with your healthcare provider are recommended so you can periodically reevaluate the benefits and risks of continuing or discontinuing HRT.
