Testosterone and male cognitive performance in Tsimane forager-horticulturalists

Objective: Testosterone plays a vital role in brain function and behavior. Among humans, age-related decline in testosterone is associated with declining cognitive functioning, and aging men with higher testosterone maintain better cognitive performance. However, most research focuses on industrialized populations with widespread access to formal schooling, high testosterone, and low parasite and pathogen load. We examine whether men's testosterone is associated with cognitive performance among Tsimane forager-horticulturalists of Bolivia despite relatively lower levels of testosterone and higher immune burden. Methods: Ninety-four Tsimane men aged 36-86 (median=49) participated in a cognitive battery (assessing short- and long-term recall, digit span, semantic memory, and visual scan) and provided urine and blood samples to measure testosterone and markers of immune activation. Linear mixed effects regressions were used to model associations between cognitive performance and testosterone, controlling for age, years of schooling, Spanish fluency, and village residence. For a subset (n=66) we included immune activation markers to examine mediator effects. Results: Testosterone is positively associated with short- and long-term verbal memory (β=0.267, P=0.018; β=0.326, P=0.005 respectively) and visual scanning (β=0.306, P=0.008) after controlling for potential confounders. Markers of immune activation were negatively associated with cognitive function, but did not change the associations between testosterone and cognitive performance. Conclusion: Tsimane men show positive associations between testosterone and cognitive performance, particularly for recall and visual scanning, despite higher immune burden. Testosterone may help motivate both physical and cognitive capacities that were essential for extracting the difficult-to-acquire, high-quality resources upon which humans relied over evolutionary history.