BETHESDA, MARYLAND. Researchers at the National Institute of Aging have found an association between the level of circulating free testosterone and the development of Alzheimer's disease (AD). Their study involved 574 men who joined the Baltimore Longitudinal Study of Aging since 1958 at ages between 32 and 87 years. The men had their total testosterone and sex hormone binding globulin (SHBG) measured at baseline and several times thereafter during an average 19-year follow-up period. The researchers found that a low free testosterone index (FTI) was associated with an increased risk of AD both at baseline and at the last measurement before the actual diagnosis of AD. FTI is equal to total serum testosterone level divided by SHBG level. Neither total testosterone nor SHBG levels, on their own, were associated with AD risk. Patients diagnosed with AD were approximately 7 years older than men not diagnosed with AD and also tended to be leaner (lower body mass index). Age and smoking were associated with increased risk, whereas education, BMI, diabetes, and hormone supplementation were associated with a reduced risk. After adjusting for all other variables the researchers concluded that each 10-unit increase in FTI corresponds to a 26% reduction in the risk of AD. They urge large-scale clinical trials to see if supplementation with testosterone might reduce the risk of Alzheimer's disease.
Moffat, SD, et al. Free testosterone and risk for Alzheimer disease in older men. Neurology, Vol. 62, January 2004, pp. 188-93
Henderson, VW and Hogervorst, E. Testosterone and Alzheimer's disease: Is it men's turn now? Neurology, Vol. 62, January 2004, pp. 170-71
Editor's comment: Testosterone supplementation should be approached with great caution and only done with the cooperation of a physician as it may increase the risk of prostate cancer.