Coronary heart disease mortality and hormone therapy before and after the Women's Health Initiative.

Objective: To assess whether coronary heart disease mortality in Finnish hormone therapy (HT) users differed before and after 2002 when the Women's Health Initiative study was published.

Methods: The risks of coronary heart disease death in HT users in relation to the age-matched background population were compared between the pre- (1995-2001) and post- (2002-2009) Women's Health Initiative eras. We used a nationwide register on HT (ie, estradiol with or without progestin) reimbursement and linked them to causes of death in 290,272 women aged 40 years or older.

Results: Exposure to HT for 1 year or less was accompanied by a 29% reduction (0.71; 0.63-0.80; three per 10,000 fewer deaths) and an exposure of 1-8 years with a 43% reduction (0.57; 0.48-0.66; three per 10,000 fewer deaths) in the risk of coronary heart disease death in the pre-Women's Health Initiative era. In the post-Women's Health Initiative era, HT use of 1 year or less was associated with an 18% reduction (0.82; 0.76-1.00; one per 10,000 fewer deaths) and an exposure of 1-8 years with a 54% reduction (0.46; 0.32-0.64; two per 10,000 fewer deaths) in coronary heart disease mortality. Discontinuation of HT was associated with an increased risk of cardiac death of 42% (1.42; 1.17-1.71; seven per 10,000 extra deaths) in the pre-Women's Health Initiative era and 31% (1.31; 0.92-1.82; two per 10,000 extra deaths) in the post-Women's Health Initiative era during the first posttreatment year. This risk increase vanished in further follow-up during both eras.

Conclusion: Changes in HT use after the Women's Health Initiative failed to affect coronary heart disease mortality of HT users in this nationwide study.