Postmenopausal estrogen replacement therapy and risk of AD - A population-based study

Objective: To study the association between estrogen replacement therapy in postmenopausal women and AD using a case-control design. Background: Studi es of the effect of estrogen therapy on the risk of AD have been limited an d have yielded conflicting results. Methods: Case patients were all postmen opausal women who developed AD in the quinquennium 1980 through 1984 in Roc hester, MN (n = 222). One control subject from the same population and free of dementia was matched to each case patient by age (+/-3 years) and lengt h of enrollment in the records-linkage system (n = 222). Estrogen exposure was defined as any form of' estrogen (oral, parenteral, topical, suppositor y) used for at least 6 months after the onset of menopause and before the o nset of AD (or corresponding year in the matched control subject). Informat ion on dose and duration of use was abstracted. Consistent with the matched design, analyses entailed conditional logistic regression. Results: AD pat ients and control subjects had identical age at menarche (median: 13.0 vers us 13.0 years) and age at menopause (median: 50.0 versus 50.0 years). The f requency of estrogen use was higher among control subjects than AD patients (10% versus 5%; odds ratio = 0.42; 95% confidence interval 0.18 to 0.96; p = 0.04). There was a significant trend of decreasing odds ratios with incr easing duration of use. The inverse association between estrogen therapy an d AD remained significant after adjustment for education and age at menopau se. Conclusion: These results from a population-based study suggest that es trogen replacement therapy is associated with a reduced risk of AD in postm enopausal women.