Endogenous estradiol in elderly individuals: cognitive and noncognitive associations

To investigate an association between endogenous estradiol (E(2)) levels and cognition and behavior in elderly individuals.

We studied 135 community-based men and women aged 52 to 85 years in urban Bangkok, Thailand; 72 had dementia and 63 did not.

Dementia was diagnosed using Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria after appropriate investigations. Blood samples for assay were collected in the morning after 6 hours of fasting. Levels of E(2) were measured by radioimmunoassay (double antibody technique). The Thai version of the Mini-Mental State Examination was used to assess cognition; the Neuropsychiatric Inventory was used to assess neuropsychiatric symptoms; and the Functional Assessment Questionnaire was used to assess instrumental activities of daily living.

There was no correlation between age and level of E(2) in either men or women. Individuals with lower estrogen levels had more behavioral disturbances (men: r = -0.467, n = 45; P =.001; women: r = -0.384, n = 90; P<.001) and worse cognition (men: r = 0.316, n = 45; P =.03; women: r = 0.243, n = 90; P =.02) and function (men: r = -0.417, n = 45; P =.004; women: r = -0.437, n = 90; P<.001). The threshold level of endogenous E(2) in elderly individuals for the risk of developing dementia was less than 15 pg/mL (<55 pmol/L) in men and less than 1 pg/mL (<4 pmol/L) in women.

Lower E(2) levels are correlated with poor cognitive, behavioral, and functional status in older individuals.