In the world of estrogen, every new study seems to reach a different conclusion. No wonder, then, that trying to keep up with the latest medical thinking on estrogen is bound to be confusing.

The early research suggested that taking estrogen, a hormone produced by women's ovaries, might help with memory loss and other Alzheimer's symptoms. But then larger studies showed that estrogen had no real effect. Still other data suggested that estrogen might help prevent, rather than treat, the disease. Now, a new study shows that an estrogen skin patch given to women with mild to moderate Alzheimer's disease can indeed improve their memory and attention skills.

"These results are hopeful, but they need to be confirmed with larger studies with more participants and longer treatment times," said study author Sanjay Asthana, MD, who conducted the study while at the VA Puget Sound Health Care System in Tacoma, Wash., and who is now at the University of Wisconsin School of Medicine in Madison.

Estrogen is familiar to many women as a treatment for the symptoms of menopause. It has been widely and successfully used for this purpose, although there is a down side; it may cause heart problems, as well as increase a women's risk of developing breast cancer.

What should women who are concerned about Alzheimer's do with this new information? According to TheDoctor's gerontology expert, Dr. John Morley, Dammert Professor of Gerontology at St. Louis University Medical School and Director of the Geriatric Research Education and Clinical Center at the St. Louis V.A. Medical Center, "The concept that estrogen may improve memory is not a new one. Both epidemiological and clinical studies have found some positive effects. However, these effects have been generally small. For now, the bottom line is that while this study is of interest there is insufficient scientific evidence to take estrogen for its effects on memory. This is especially true in light of some of the health risks associated with estrogen. Certainly, because of potential adverse effects on the heart, estrogen should not be taken by women who are more than five years past menopause."

In Dr. Asthana's study, women were given tests to measure their attention skills, recent and visual memory, and their ability to name common items from pictures. Those receiving estrogen scored 20 percent higher on an attention test than women receiving a placebo. They did 35 and 30 percent better on tests of recent verbal and visual memory and 10 percent better on tests of semantic memory.

Asked what could explain the differences between his study and those that found no memory-enhancing effect, Dr. Asthana pointed out that he used estradiol, a type of estrogen that has been shown to have an effect on the brain. Other studies investigated shorter-acting and weaker types of estrogen, such as estriol, which would have reduced their effect on the brain. Also worth noting is the fact that the largest study which found no effect included only women who had hysterectomies. "We don't know enough yet about how a hysterectomy versus no hysterectomy can affect the brain's response to estrogen," he said.

Scientists are still learning how estrogen works in the brain but the hormone seems to protect brain cells and may boost the level of the neurotransmitter, acetylcholine, a chemical that carries messages between brain nerve cells, a process which Alzheimer's disease disrupts. The study was published in the August 28, 2001 issue of Neurology, the scientific journal of the American Academy of Neurology.

Reviewed by: John E. Morley, M.D.