Researcher Robert Greene, MD, tells WebMD that he believes the blood flow decreases are a "triggering event" for Alzheimer?s -- meaning that they may contribute to onset of the disease. When the brain doesn?t receive enough blood, minor injuries occur that can lead to death of the brain cells and aging of certain nerves in the affected area.
Greene is a reproductive endocrinologist at The North State Women's Center in Redding, Calif.
Greene and his colleagues conducted a study involving 12 healthy menopausal women who were experiencing daily hot flashes. Blood flow was measured when the women were feeling "normal" -- not experiencing hot flashes -- and when hot flashes were occurring. The measurements were taken again after the women had received 6 weeks of treatment with either estrogen or a non-active pill (placebo).
The researchers found that blood flow declined substantially during hot flashes -- a time when all the women in the study showed blood-flow patterns similar to those found in patients with Alzheimer?s. The women who took the estrogen had an average 22% increase in cerebral blood flow compared with the placebo group. The largest increase was in the left temporal region, which is typically affected by Alzheimer?s disease.
Brain function also improved for the women who took estrogen, but the increase was not considered significant. In an interview with WebMD, Greene says, "The suggestion of this data is that ERT might help diminish" the cell death and nerve aging that lead to Alzheimer?s disease. He hopes to obtain further, more solid results when he repeats the study with 100 women who will be studied for 3 months.
In the meantime, Greene says that physicians and researchers should keep the study?s findings in mind when treating postmenopausal patients, since women are three times more likely than men to develop late-onset Alzheimer?s. At the very least, Greene says that physicians need to consider the possibility that hot flashes are clinically important and not just a nuisance. The risks of brain harm would be especially great in women who experience hot flashes for many years, he notes.
Jennifer Larsen, MD, chief of endocrinology at the University of Nebraska Medical Center, Omaha, tells WebMD that Greene is among a growing number of researchers "who have suggested that vascular changes contribute to Alzheimer's." But she cautions that Greene?s study does not contain enough data to draw major conclusions.
It will not be easy to show that estrogen has an effect on brain function in postmenopausal women, according to Larsen, because some changes may be due to other factors. For example, Larsen days, "these women may appear to have better cognitive function because they sleep better at night once they stop having hot flashes."