WEDNESDAY, May 2, 2007 (HealthDay News) -- Women who start hormone therapy earlier in life -- before they turn 65 -- could cut their risk of developing Alzheimer's or another dementia, a new study suggests.
This stands in contrast to findings on using hormone replacement therapy (HRT) after age 65, which appears to increase the risk of dementia.
"The magnifying glass has moved slightly earlier, and it looks like, if women started taking HRT early, they did show a decreased risk of Alzheimer's," said Dr. Sam Gandy, chairman of the Alzheimer's Association's medical and scientific advisory council, and director of the Farber Institute for Neurosciences at Thomas Jefferson University in Philadelphia.
But the study authors urged caution in interpreting the findings.
"The findings are of interest to the research community. It's harder to say how they should inform or dictate clinical practice," said Dr. Victor Henderson, presenting author and a professor of health research and policy and neurology and neurological science at Stanford University in Palo Alto, Calif. "Our findings suggest that more research needs to be done looking at the late consequences of early hormone therapy. The analyses are observational, which are weaker than experimental, so there's room for error. Be cautious with the clinical implications."
Henderson was expected to present the findings Wednesday at the American Academy of Neurology annual meeting, in Boston.
Hormone therapy in older women seems to increase the risk for different dementias. But, in younger postmenopausal women, the relationship between hormone therapy and Alzheimer's disease is less clear.
Previous research had suggested that low levels of estrogen in the brain may raise the risk for developing Alzheimer's, which could be an argument for using HRT.
For the new research, part of the Women's Health Initiative Memory Study, 7,153 women aged 65 to 79 without dementia provided information on past hormone therapy exposure.
Women who reported using any form of estrogen hormone therapy before they turned 65 were nearly 50 percent less likely to develop Alzheimer's disease or another dementia than women who did not use such therapy by that age.
But women who started estrogen-only therapy after the age of 65 had about a 50 percent increased risk of developing dementia. The risk was nearly double among women using combined (estrogen plus progestin) therapy.
The study was funded by the U.S. National Institutes of Health and Wyeth, a pharmaceutical company that makes Prempro, a hormone therapy.
Gandy had a possible biological explanation for differences observed in younger and older postmenopausal women.
"I think about it biologically. If you give HRT early, you prevent menopause from ever happening. The brain never sees menopause," Gandy said. "But if you allow menopause to happen, the brain goes from 30 years of a hormone-rich environment to a hormone-deficient environment, then a reintroduction of hormones after menopause. I think the brain reacts to those two scenarios very differently.
"What we're learning is, if there's anything here in terms of HRT and Alzheimer's, it has to be early," he continued. "This is the first signal from a randomized, placebo-controlled, well-designed study that this early initiation may be the way to go. [But] it's a very complicated situation that we don't have our arms around completely."
But when it comes to hormone replacement therapy, official guidelines recommend that women take HRT for relief of menopausal symptoms only and then at the lowest dose possible for the shortest period of time possible. Extended use of hormone therapy has been linked to a variety of significant health problems, including breast cancer, heart attack and stroke.
The Alzheimer's Association can tell you more about Alzheimer's disease.