Androgen receptor CAG repeat polymorphism is associated with cognitive function in older men.

Background: Androgen receptors are located throughout the brain, especially in regions involved with learning and memory. Different lengths of a CAG (glutamine) repeat polymorphism in exon 1 of the androgen receptor gene may influence androgen action, with longer repeat lengths conferring decreased androgen sensitivity.
Methods: We sought to determine if this CAG polymorphism was associated with cognition in older men.
Results: Among 301 community-dwelling white men (mean age, 73.0 +/- 7.1), greater CAG repeat length was associated with lower scores on three cognitive tests (p <.05 for all). In addition, 12 participants (9.8%) had cognitive impairment in the low tertile of CAG repeat length whereas 29 (16.3%) had cognitive impairment in the two higher tertiles (odds ratio = 1.8; 95% confidence interval =.9-3.7).
Conclusions: Research should be directed at identifying the mechanism for this association and to determine if treatment with testosterone prevents cognitive decline.