Objective: To examine the effect of postmenopausal estrogen therapy (ET), including duration and recency of use, on all-cause mortality in older women.
Design: As part of a prospective cohort study of residents of a California retirement community begun in the early 1980s, Leisure World Cohort women (median age, 73 y) completed a postal health survey including details on ET use and were followed up for 22 years (1981-2003). Age- and multivariate-adjusted risk ratios (RR) and 95% CIs were calculated using proportional hazard regression.
Results: Of the 8,801 women, 6,626 died during follow-up (median age, 88 y). ET users had an age-adjusted mortality rate of 52.9 per 1,000 person-years compared with 56.5 among lifetime nonusers (RR = 0.91; 95% CI, 0.87-0.96). Risk of death decreased with both increasing duration of ET and decreasing years since last use (P for trend <0.001). The risk was lowest among long-term (> or =15 y) users (RR = 0.83; 95% CI, 0.74-0.93 for 15-19 y and RR = 0.87; 95% CI, 0.80-0.94 for 20+ y). For long-term users, the age-adjusted mortality rate was 50.4 per 1,000 person-years. Lower-dose users (< or =0.625 mg) had a slightly better survival rate than higher-dose users (RR = 0.84; 95% CI, 0.78-0.91 vs RR = 0.91; 95% CI, 0.83-0.97). Risk did not differ by route of administration (P = 0.56). Further adjustment for potential confounders had little effect on the observed RRs for ET.
Conclusion: Long-term ET is associated with lower all-cause mortality in older women.