Changes in pattern of use, clinical characteristics and persistence rate of hormone replacement therapy among postmenopausal women after the WHI publication

The WHI was stopped prematurely because of an increased risk of breast cancer, stroke and cardiovascular diseases (CVD) in the hormone replacement therapy (HRT) arm of the trial. Changes in the use of HRT are expected. Objective: To assess the impact of the Women's Health Initiative (WHI) publication on the rate of HRT prescription, and the clinical characteristics and persistence rate of new users and its determinants. Methods: From the RAMQ databases, the total numbers of HRT prescriptions, and of new HRT's users were calculated between 2 January 1998 and 31 May 2003. To assess the clinical characteristics of women, two retrospective cohorts of new HRT's users were constructed before (pre-WHI) and after (post-WHI) the WHI study publication. The persistence rate after 1 year of follow-up was estimated using a Kaplan-Meier analysis. Cox regression models were used to estimate the rate ratio of HRT cessation. Results: The total numbers of HRT users and of new users declined respectively by 28% and 50% in post-WHI. The standard dosage of HRT was significantly less used, while the proportion of women with risk factors of CVD or at very high risk of coronary artery disease (CAD) did not change. The rate of persistence in the pre-WHI cohort was 59% compared to 45% in the post-WHI (p < 0.0001), and women with risk factors of CVD or at very high risk of CAD were less likely to cease their HRT. Conclusion: One year after publication, significant changes had already occurred in the trends of use, women's characteristics and estrogen dosage. No change in the proportion of new users with CVD risk factors or at very high risk of CAD was seen.