Hormone replacement therapy does not improve the cognitive ability of postmenopausal women with Alzheimer's disease, according to a large study reported in the February issue of the Archives of Neurology.

The study contradicts results from two recent small clinical trials involving 12 and 20 women that found that higher doses of estrogen delivered in patch form improved attention and verbal memory.

Over a one-year period, University of California at San Diego (UCSD) researchers studied 120 postmenopausal women with Alzheimer's disease. The participants were either given a placebo or varying does of Premarin, a hormone-replacement therapy that raises the levels of the hormones estradiol and estrone.

UCSD researchers drew blood samples from the study participants to assess estradiol and estrone levels. Participants also took several tests to determine the relationship between a change in hormone levels and a change in cognition.

"We attained the same high levels of hormone that the two small clinical trials attained, but our larger study showed no improvement in cognition," said researcher Dr. Leon Thal, UCSD professor of neurosciences and a neurologist with the San Diego VA Healthcare System.

Other sources: University of California - San Diego