Estrogen for Alzheimer's

It’s been unclear whether hormone therapy helps older women reduce their risk of Alzheimer’s or in fact increases the risk. To date, the research has been inconsistent, with observational studies showing a reduced risk, and a large randomized controlled trial showed an increased risk. As mentioned before, the answer to the inconsistency may lie in the timing of the therapy. A new study supports this view.

The 11-year study (part of the Cache County Study) involved 1,768 older women (65+), of whom 1,105 women had used hormone therapy (either estrogen alone or in combination with a progestin). During the study, 176 women developed Alzheimer's disease. This included 87 (7.9%) of the 1,105 women who had taken hormone therapy, and 89 (13.4%) of the 663 others.

Women who began hormone therapy, of any kind, within five years of menopause had a 30% lower risk of developing Alzheimer's within the study period (especially if they continued the therapy for 10 or more years). Those who began treatment more than five years after menopause, had a ‘normal’ risk (i.e., not reduced or increased). However, those who had started a combined therapy of estrogen and progestin when they were at least 65 years old had a significantly higher risk of developing Alzheimer’s.

The findings support the idea that the timing of hormone therapy, and the type, are critical factors, although the researchers cautiously note that more research is needed before they can make new clinical recommendations.

Older news items (pre-2010) brought over from the old website

For women over 65, Combined Hormone Therapy increases risk of dementia

Much to the researchers’ surprise and disappointment, a four-year experiment involving 4,532 women at 39 medical centers, has found that combined hormone therapy (involving both estrogen and progestin) doubles the risk of Alzheimer's disease and other types of dementia in women who began the treatment at age 65 or older, although the risk is still small : for every 10,000 women 65 and older who take hormones, 23 of the predicted 45 cases of dementia a year, will be attributable to the hormones. The study also found that the combined hormone therapy produced no improvement in general cognitive function, and in fact had adverse effects on cognition among some women. This supports an earlier study suggesting that, while estrogen is helpful to cognitive function in postmenopausal women, the benefits can be cancelled out by progestin / progesterone. The study also confirmed previous research showing that the combination therapy increased the risk of stroke - previous research has indicated that risk factors for stroke are also risk factors for cognitive decline.

Shumaker, S.A., Legault, C., Rapp, S.R., Thal, L., Wallace, R.B., Ockene, J.K., Hendrix, S.L., Jones, B.N. III, Assaf, A.R., Jackson, R.D., Kotchen, J.M., Wassertheil-Smoller, S. & Wactawski-Wende, J. 2003. Estrogen Plus Progestin and the Incidence of Dementia and Mild Cognitive Impairment in Postmenopausal Women: The Women's Health Initiative Memory Study: A Randomized Controlled Trial. JAMA, 289, 2651-2662.

Rapp, S.R., Espeland, M.A., Shumaker, S.A., Henderson, V.W., Brunner, R.L., Manson, J.E., Gass, M.L.S., Stefanick, M.L., Lane, D.S., Hays, J., Johnson, K.C., Coker, L.H., Dailey, M. & Bowen, D. 2003. Effect of Estrogen Plus Progestin on Global Cognitive Function in Postmenopausal Women: The Women's Health Initiative Memory Study: A Randomized Controlled Trial. JAMA, 289, 2663-2672.

Wassertheil-Smoller, S., Hendrix, S., Limacher, M., Heiss, G., Kooperberg, C., Baird, A., Kotchen, T., Curb, J.D., Black, H., Rossouw, J.E., Aragaki, A., Safford, M., Stein, E., Laowattana, S. & Mysiw, W.J. 2003. Effect of Estrogen Plus Progestin on Stroke in Postmenopausal Women: The Women's Health Initiative: A Randomized Trial. JAMA, 289, 2673-2684.

Animal studies suggest why estrogen can't help after dementia has developed

Research with rats suggests that nerve cells in the brain called cholinergic neurons are needed for estrogen to help learning and memory. This suggests why starting estrogen after dementia has developed is ineffective.

Gibbs, R.B. 2002. Basal Forebrain Cholinergic Neurons Are Necessary for Estrogen to Enhance Acquisition of a Delayed Matching-to-Position T-Maze Task, Hormones and Behavior, 42(3), 245-257.

Long-term ERT in postmenopausal women with Alzheimer's may worsen memory

A study using female rats investigated the interaction of two conditions known to exist within the brains of female Alzheimer's patients: 1) the presence of chronic neuroinflammation, and 2) having too much or not enough estrogen. They found that rats who had their ovaries removed (to model the condition of post-menopausal women) performed more poorly on a water maze task when they had chronic brain inflammation OR long-term estrogen replacement therapy. Most significantly, those who had both conditions performed much more poorly – beyond what would be expected by either condition alone. That such results extend to postmenopausal women is supported by a 2000 study involving a long term, placebo-controlled study that examined the effects of estrogen replacement therapy on cognitive function in women with mild to moderate Alzheimer's. The effects of ERT were initially beneficial, but the performance of women receiving sustained ERT declined more than that of women receiving the placebo treatment. The results of these studies suggest that postmenopausal women with Alzheimer's disease who undergo long-term estrogen replacement therapy may make their memory loss worse.

Marriott, L.K., Hauss-Wegrzyniak, B., Benton, R.S., Vraniak, P.D. & Wenk, G.L. 2002. Long-Term Estrogen Therapy Worsens the Behavioral and Neuropathological Consequences of Chronic Brain Inflammation. Behavioral Neuroscience, 116 (5), 902-11.

Estrogen patch may improve memory for women with Alzheimer's

A new study suggests that an estrogen skin patch given to women with mild to moderate Alzheimer's disease can improve their memory and attention skills. The study involved only 20 women for eight weeks, and the results will need to be confirmed by a larger-scale study. Research to date has been equivocal about the effects of estrogen on women with Alzheimer's, with some finding a memory-enhancing effect, and others finding no effect. It is speculated that the type of estrogen might be critical. The present study used estradiol, a type of estrogen that has been shown to have an effect on the brain.

Asthana, S., Baker, L. D., Craft, S., Stanczyk, F. Z., Veith, R. C., Raskind, M. A., & Plymate, S. R. (2001). High-dose estradiol improves cognition for women with AD Results of a randomized study. Neurology, 57(4), 605–612. doi:10.1212/WNL.57.4.605