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Thursday March 12 Estrogen And Brain Function: More Data Needed NEW YORK (Reuters) -- Several studies have suggested that estrogen replacement therapy in postmenopausal women can improve cognitive function, cut down on risk of developing dementia, and -- if dementia does occur -- lessen its severity. But other studies have found no such effects. After reviewing relevant published studies, a team of San Francisco researchers conclude that more data is needed before estrogen can be recommended as a therapy to prevent dementia. Dr. Kristine Yaffe, along with her colleagues from the University of California, San Francisco, conducted an exhaustive search of the medical literature from 1966 through 1997. They looked at the results of studies that focused on the effects on cognition (memory and learning) or on the risk of dementia in patients taking estrogen. They then evaluated the conclusions of those studies and the methods researchers used to come to those conclusions. The studies suggest several mechanisms by which estrogen might affect cognition: by promoting neurochemical activity in specific regions of the brain; by keeping neurons in good repair; by affecting lipoproteins in positive ways; or by maintaining circulation in the brain. The researchers found 13 studies published since 1966 that addressed the effect of estrogen on cognitive function in healthy postmenopausal women. "The largest and most methodologically sound observational study of the effect of estrogen use on cognition in nondemented women showed no benefit," the researchers write. A combined analysis of 10 studies looking at the effects of estrogen use in preventing dementia indicates that estrogen use cuts a woman's chances of developing dementia by 29%. But the researchers caution that results from those studies were diverse, so that combining the data may not produce the most accurate figures. Looking at four trials of estrogen use in women with Alzheimer's disease, the team found that all four had essentially positive results. But they say those studies were small and of short duration and that they were neither randomized nor controlled. The authors conclude that although the studies they evaluated provide plausible reasons to believe that estrogen replacement may improve cognitive function, decrease risks of dementia, or lessen the severity of dementia, there are nonetheless "substantial methodologic problems" with that research. They say large, placebo-controlled trials are needed to sort out estrogen's role in preventing and treating Alzheimer's and other forms of dementia. But until then? "Given the known risks of estrogen therapy, we do not recommend estrogen for the prevention or treatment of Alzheimer disease or other dementias until adequate trials have been completed," the researchers conclude. SOURCE: The Journal of the American Medical Association (1998;279:688-695) [log in to unmask] (Judith Richards)