Endogenous sex hormone levels and cognitive function in aging men - Is there an optimal level?

Objective: To determine whether endogenous sex hormone levels are associated with cognitive functioning in men. Methods: Cognitive performance was assessed in 400 independently living men between ages 40 and 80 in a population-based cross-sectional study. Compound scores were calculated for memory function, processing capacity/speed, and executive function. The Mini-Mental State Examination was used as a measure of global cognitive function. The adjusted association of testosterone (T) and estradiol (E-2) (total, bioavailable) with neuropsychological test scores in the total group and in subgroups was assessed by linear and logistic regression analysis. Results: Curvilinear associations were observed between T and memory performance and processing capacity/speed, suggesting optimal sex hormone levels. No association between E-2 and cognitive functioning was found. After the population was subdivided into four age decades, a linear association of T with cognitive functioning in the oldest age category remained. No association was found in the other age decades. Lower bioavailable T levels were associated with lower scores on processing capacity/speed and executive function; beta (95% CI) values were 0.36 (0.07 to 0.66) and 0.17 (-0.01 to 0.35). Similar results were observed for total T. Conclusions: Higher testosterone (T) levels are associated with better cognitive performance in the oldest age category. Apparent curvilinear associations between T and certain cognitive functions in men suggest an optimal hormone level for particular cognitive tasks and are explained by linear associations in the oldest age category.