Low level of testosterone increases risk for Alzheimer's disease

Low levels of the male sex hormone, testosterone, in older men is associated with the onset of Alzheimer's disease, according to research by a team that includes a Saint Louis University scientist.

"Having low testosterone may make you more vulnerable to Alzheimer's disease," said John E. Morley, M.D., director of the division of geriatric medicine at Saint Louis University and a study co-investigator. "The take-home message is we should pay more attention to low testosterone, particularly in people who have memory problems or other signs of cognitive impairment."

The study was published electronically http://www.ncbi.nlm.nih.gov/pubmed/20693646 prior to its print publication in the Journal of Alzheimer's Disease and led by Leung-Wing Chu, M.D., who is chief of the division of geriatric medicine at Queen Mary Hospital at the University of Hong Kong.

Researchers studied 153 Chinese men who were recruited from social centers. They were at least 55 years and older, lived in the community and didn't have dementia. Of those men, 47 had mild cognitive impairment - or problems with clear thinking and memory loss.

Within a year, 10 men who all were part of the cognitively impaired group developed probable Alzheimer's disease. These men also had low testosterone in their body tissues; elevated levels of the ApoE 4 (apolipoprotein E) protein, which is correlated with a higher risk of Alzheimer's disease; and high blood pressure.

"It's a very exciting study because we've shown that a low level of testosterone is one of the risk factors for Alzheimer's disease," Morley said.

The findings corroborate findings in previous studies of older Caucasian men that show low testosterone is associated with impaired thinking and Alzheimer's disease. They suggest that testosterone may have a protective value against Alzheimer's disease.

The next step, Morley said, is to conduct a large-scale study that investigates the use of testosterone in preventing Alzheimer's disease. Morley and his co-authors advocate studying the effectiveness of testosterone replacement in older men who have both mild memory problems and low testosterone in staving off Alzheimer's disease.