Sept. 24, 2004 -- Could hormone replacement therapy for men keep men's minds healthy and reduce the risk of Alzheimer's disease? A new study suggests that declining testosterone in aging men may put them at risk for the memory-robbing disease.
Researchers say testosterone levels naturally fall as men get older, which increases the risk of a variety of disorders, such as osteoporosis. But it's unclear if these normal hormonal changes may also affect the brain and play a role in increasing the risk of developing Alzheimer's disease.
In their study, researchers compared testosterone levels in the brain tissue of deceased men with Alzheimer's vs. non-affected deceased men of the same age. They found testosterone levels were significantly lower in the men with Alzheimer's disease compared with the men who did not have the disease.
In addition, testosterone levels were also much lower in men with early symptoms of the disease compared with men without Alzheimer's.
"Our findings strongly suggest that normal age-related testosterone depletion is one of the important changes that promote Alzheimer's disease in men," says researcher Christian Pike, assistant professor at the University of Southern California Leonard Davis School of Gerontology, in a news release. "Understanding how these changes increase vulnerability to the disease is critical not only for elucidating Alzheimer's development, but also for identifying those persons most at risk."
The results of the study appear in the current issue of The Journal of the American Medical Association.
Researchers say the findings are significant because only testosterone levels appeared related to Alzheimer's risk, while estrogen levels in the brain tissue were not affected by advancing age or the presence of Alzheimer's disease.
Despite these findings, researchers say it is still possible that low brain testosterone levels may be a byproduct of Alzheimer's disease rather than a contributing factor. They say more research is needed.
However, they say animal studies suggest testosterone may have several beneficial effects on the brain and help protect it from disease.
"Thus far, our research tells us that testosterone has at least two critical brain functions relevant to Alzheimer's disease," Pike says. "It protects neurons from injury, and it reduces levels of beta-amyloid, the protein widely implicated as a causal factor in the disease."