Testosterone and dementia: too much ado about too little data

In vitro and animal investigations have indicated that testosterone is neuroprotective and reduces the levels of beta-amyloid and the phosphorylation of tau (which are considered to be critical to the pathophysiological process that leads to the development of Alzheimer's disease (AD)). Such findings imply that testosterone may have an important role in the modulation of cognitive function and in reducing the risk of AD. Currently available clinical evidence of the association between testosterone and cognitive function/AD comes from a small number of cross-sectional studies and five randomised trials of testosterone supplementation for healthy older men. The results suggest that testosterone has a weak association with visuospatial and memory scores, but the findings are inconsistent across different studies, which often included multiple comparisons across a wide range of cognitive domains. In addition, the serum levels of testosterone in men with AD are comparable to those of controls, as are brain levels. In conclusion, currently available evidence does not support the existence of a strong association between testosterone and cognitive function/AD.