The jury is still out on whether estrogen might be an effective treatment for Alzheimer’s disease.

In some small clinical studies, for example, estrogen therapy improved cognitive function in patients with Alzheimer’s disease. A large, year-long clinical trial reported in the February 23 Journal of the American Medical Association, however, failed to substantiate these findings.

In contrast, several studies have indicated that estrogen might help prevent Alzheimer’s disease, and now still another study, this one conducted by two researchers at the National Institute on Aging in Bethesda, Md., appears to bolster this possibility. The findings were published in the April/May issue of Neurobiology of Aging.

Pauline Maki, Ph.D., and Susan Resnick, Ph.D., had 28 cognitively healthy women—12 of whom were using estrogen replacement therapy and 16 of whom were not—view pictures of 20 objects and a list of 20 words on a computer screen. The women were then shown a series of words or figures—some that they had seen earlier on the computer screen and others that they had not seen before

As the subjects viewed these words or figures, they were instructed to indicate whether they had seen them previously. As they tried to remember, the women were given PET scans. The scans measured blood flow to regions of their brains that are involved in memory and also implicated in the development of Alzheimer’s. These regions include the hippocampus, parahippocampal gyrus, and middle temporal lobe.

The women were then given the same memory tests two years later, and once again, as they tried to remember what they had seen, PET scans were used to measure blood flow to areas of their brains involved in memory and Alzheimer’s.

The researchers then compared the blood flow to memory areas at baseline with the blood flow to memory areas two years later in the estrogen takers. They also compared the blood flow to memory areas at baseline with the blood flow to memory areas two years later in the control subjects. And then they compared the blood flow differences over the two-year period in estrogen takers with the blood flow differences over the two-year period in the controls. And what they found was a relative increase in blood flow in estrogen users compared with controls.

This finding suggests that estrogen enhances blood flow to regions of the brain that are involved in memory and Alzheimer’s disease and thus may possibly help protect a woman against Alzheimer’s. Or as Maki puts it: "It really gives us the first direct insight into how the brain responds to estrogen over time, and how estrogen might protect against normal and abnormal memory changes as we age."