TUESDAY, May 27, 2003 (HealthDayNews) -- Combined hormone therapy for women doubles the risk of dementias such as Alzheimer's disease, researchers report.
Combined hormone therapy also does not protect against mild cognitive impairment, a less severe loss of mental function, and it increases the risk of stroke.
All that bad news comes from the latest data extracted from the Women's Health Initiative study, which was stopped last year when combined hormone therapy was found to increase the risk of breast cancer and heart disease. The three studies appear in the May 28 issue of the Journal of the American Medical Association.
The new reports are based on studies of subsets of the more than 100,000 women who enrolled in the study. Two studies of mental function done by researchers at Wake Forest University School of Medicine reported data on more than 4,500 women who were taking daily doses of estrogen and progestin.
"When we began the study, combined therapy was regarded as beneficial for dementia," says Sally A. Shumaker, a professor of public health sciences at Wake Forest University and lead author of the dementia paper. "Going into the study, the expectations were that it would be beneficial, but we didn't know."
Now they know. The data show a dementia rate of 45 per 10,000 women taking the hormones, compared to 22 per 10,000 in women taking a placebo, Shumaker says.
There is some comfort in the thought that "the absolute risk for an individual woman is very small," she says. But as was true of heart disease and breast cancer, which hormone therapy was supposed to prevent, the dementia result "reinforces the finding that the risks of combined hormone therapy outweigh the benefits, especially for older women," she says.
Other researchers at Wake Forest looked at the incidence of mild cognitive impairment in the women in the study. Periodic tests of mental function showed no significant benefit and a possible harmful effect of hormone therapy, another report says.
Combined hormone therapy now is recommended only for short-term use in women suffering extreme problems during menopause. The problem, says Sylvia Wassertheil-Smoller, a professor of epidemiology and public health at Albert Einstein College of Medicine and lead author of the stroke report, is that "we don't know how short is short-term."
There are indications the risk of both dementia and stroke increases rather quickly, in a year or two, Wassertheil-Smoller says, and so "we can't make a comment on short-term use."
The stroke finding was expected and is less severe than the dementia risk, she says -- seven excess cases of stroke for every 10,000 women on hormone therapy. What the study did show is that most of the strokes are ischemic, in which a blood clot blocks a blood vessel, rather than hemorrhagic, in which a blood vessel bursts. The risk also seemed to be higher for younger women, although the difference was not statistically significant, she says.
Various parts of the study are continuing, such as one looking at the effect of a single hormone, estrogen, on women who have had a hysterectomy. Women in the dementia study are still being followed to see whether the risk decreases when they stop hormone therapy, Shumaker says.
More information
A detailed overview of the Women's Health Initiative is available from the National Institutes of Health or the U.S. Preventive Services Task Force.
