Low levels of total and bioavailable testosterone may be associated with an increased risk of dementia in elderly men, according to French investigators.

From a cohort of 3,650 men aged 65 years and older, Laure Carcaillon, MD, of Inserm in Villejuif, France, and collaborators compared 105 men with incident dementia and a random sample of 413 men without dementia. The median follow-up period was 3.1 years. Compared with the middle tertile of total testosterone (total-T) level, the lower and upper tertiles were associated with a 2.3 times and 1.9 times increased risk of dementia, respectively. Low bioavailable testosterone (bio-T) also was associated with a greater risk for dementia, especially among men aged 80 years and older, investigators reported online ahead of print in Alzheimer’s & Dementia. In men aged 80 and older, low bio-T was associated with a significant threefold increased risk of dementia; in men younger than 80, it was associated with a nonsignificant 7% increased risk.

Additionally, the risk of dementia associated with low bio-T was greater in men with a high level of education compared with men who had a low level of education.

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Taken together, the authors noted, their results support the hypothesis of a deleterious effect of low testosterone concentrations on brain aging, and also suggest that high levels of total-T could increase this risk.