Free and unbound estrogen could protect older women from cognitive decline.
August 29, 2000
NEW YORK, Aug 28 (Praxis Press). Most studies examining the association of estrogen and cognitive function in older women have measured total hormone concentrations. However, non-protein-bound (free) and loosely bound (bioavailable) forms more readily cross the blood-brain barrier and may show better correlation with cognition. Yaffe and colleagues studied the association between cognitive performance over time and baseline serum concentrations of non-protein-bound and loosely bound estradiol in 452 women age 65 years or older. Cognitive impairment occurred in 5% of women in the high tertile and 16% of women in the low tertile for non-protein-bound estradiol concentrations (adjusted odds ratio, 0.3); similar results were noted for loosely bound estradiol (adjusted odds ratio, 0.3). This pattern persisted when women taking estrogen were excluded from analysis. In contrast, cognitive impairment was not associated with concentrations of total testosterone (adjusted odds ratio, 1.5) or with concentrations of non-protein-bound testosterone (adjusted odds ratio 1.2). Serum free and bioavailable estradiol may protect older women against cognitive decline.