Objective: The aim of this study was to assess risks and benefits of conjugated equine estrogens (CEE) and medroxyprogesterone acetate (MPA) in postmenopausal Chinese women.
Methods: A retrospective cohort study was undertaken using the Taiwan National Health Insurance Research Database, a population-based healthcare claims dataset. Eligible women aged 50 to 79 years were classified as exposed to CEE 0.625 mg/day with MPA 5.0 mg/day (estrogen [E] + progestin [P], n = 4,712) or CEE 0.625 mg/day only (E-only, n = 1,208) and were age-matched to unexposed women (n = 10,125). Follow-up was complete in 96% of the participants. The primary outcomes were coronary heart disease (CHD) and invasive breast cancer. The global index summarized risks of primary outcomes, stroke, pulmonary embolism, colon and endometrial cancers, hip fractures, and death. Time-to-event analyses were performed.
Results: Median durations of exposure in the E + P and E-only groups were 6.9 and 9 months, respectively. Median follow-up was 110 months. Hazard ratios (95% CI) for E + P exposure were as follows: myocardial infarction, 0.78 (0.51-1.19); CHD death, 1.21 (0.53-2.70); breast cancer, 1.48 (1.20-1.83); global index, 0.79 (0.72-0.87). Hazard ratios for E-only exposure were as follows: myocardial infarction, 0.76 (0.35-1.68); CHD death, 0.57 (0.11-2.80); breast cancer, 1.44 (0.99-2.10); global index, 1.09 (0.92-1.28). Per 10,000 person-years, there were 12 excess breast cancer cases with E + P exposure; there were 39 fewer global index events with E + P exposure. Adjusting for age, statin and aspirin use, hypercholesterolemia, diabetes, and hypertension did not significantly change estimates.
Conclusions: In postmenopausal Chinese women, CEE with or without MPA was not associated with increased rates of CHD, but CEE with MPA may be associated with a higher breast cancer rate. E + P exposure conferred lower global index event rates.