Q. The Women's Health Initiative found that hormone therapy wasn't helpful for avoiding dementia; there was some suggestion that it might even cause cognitive problems. Am I at risk for dementia by continuing hormone therapy?

A. You're right about the results of the Women's Health Initiative Memory Study (WHIMS), the largest clinical trial to date of the effects of hormone therapy (HT) on cognitive function and dementia. Women ages 65 to 79 took HT (estrogen alone or estrogen combined with a progestin) or a placebo. After four to five years, the researchers found that taking HT didn't improve cognitive function. Moreover, the women who took combined estrogen and progestin were twice as likely as the placebo takers to develop dementia.

These findings don't square with animal and laboratory studies suggesting a favorable effect of estrogen on cognitive function. And there's strong biological evidence that estrogen is important for brain function in women. Estrogen receptors are found throughout the brain, and many interactions take place between the brain and the reproductive endocrine system. Some research suggests that ovary removal during hysterectomy increases the risk of cognitive problems, presumably due to the loss of estrogen.

So what accounts for the WHIMS results? Some researchers think the problem is in the timing; they suggest that HT is more likely to benefit the brain if it's started in early menopause. A five-year clinical trial called the Kronos Early Estrogen Prevention Study (KEEPS) is now addressing this question. Results are expected in 2011.

Based on what we know right now, HT won't improve your thinking or stave off dementia. But could it increase your risk for cognitive problems? Here the evidence is less compelling. We do know that taking HT increases the risk for several serious conditions, including blood clots, stroke, heart attack, and breast cancer (when estrogen is combined with a progestin). Unless you have burdensome hot flashes or vaginal atrophy that can't be controlled any other way, I suggest that you taper off HT, which is recommended only for the short-term relief of such symptoms.

There are several non-hormonal, risk-free strategies that may help your memory and thinking, including these: get regular exercise; keep learning -- through work, hobbies, or pursuits such as reading; get enough sleep; and review your medications, to make sure you're not taking anything that could interfere with your thinking.

-- Celeste Robb-Nicholson, M.D., Editor in Chief, Harvard Women's Health Watch

(c) 2010 Harvard Women's Health Watch