Dementia and low testosterone and bioavailable testosterone levels in men: possible increased risk.

This study examines associations of serum total and bioavailable testosterone (T) with dementia in a community-based cohort of men. Study subjects (n=128; ages 65 y and older at baseline) were recruited in 1990 and followed through 2006. Dementia was assessed from the subject medical records on the basis of the criteria from the Diagnostic and Statistical Manual of Mental Disorders, 4th ed. Serum from a blood draw performed in 1994 was assayed for total and bioavailable T. Twenty-one men developed dementia over 1186 person-years of follow-up. The cumulative incidence of dementia was 14.7% in men with total T <410 ng/mL (median) and 8.0% in men with higher levels [>/=410 ng/mL; age-adjusted hazard ratio (HR)=2.09; 95% confidence interval (CI)=0.76, 5.75]. Similarly, the cumulative incidence of dementia was 18.8% in men with bioavailable T <12 ng/mL (median) and 2.2% in men with bioavailable T >/=12 ng/mL; age-adjusted HR=1.22 (95% CI=0.38, 3.87). These findings do not demonstrate a significant association between T levels and dementia. However, they suggest a need for further investigation of these potential associations.