Circulating levels of bioavailable testosterone and estradiol as risk factors for decline in cognition Results from the Canadian Study of Health and Aging

Abstract

Using the data from the 1991-2001 Canadian Study of Health and Aging, this study examined the association between sex hormone levels and cognitive decline. The objective was to reach a better understanding of the effect of sex steroid hormones on cognition in men and women over the age of 65. Initial hypotheses postulated the existence of a protective effect of circulating hormone levels on the risk of developing dementia. This would support the judicious use of hormone replacement therapy (testosterone and/or estradiol) in dementia; either delaying the onset of dementia or slowing its progress. The results from this study did not reveal any significant association between the circulating levels of total testosterone, bioavailable testosterone, estradiol or the E2/SHBG ratio and cognitive decline. In the logistic regression, the ORs were all very near 1 and not statistically significant. This led us to question the impact of the lack of sensitivity of assays for testosterone and estradiol because in an elderly population when the hormone levels are at their lowest. Also, the small sample size and heterogeneity in a number of diagnostic groups could account for the absence of statistical significance. (Abstract shortened by UMI.)