Background: The recent publication of clinical trial results has led to a dramatic shift in the evidence about postmenopausal hormone therapy.
Objective: To examine whether the publication of clinical trial results, specifically the Heart and Estrogen/progestin Replacement Study (HERS) in 1998 and the Women's Health Initiative (WHI) in 2002, has influenced the use of hormone therapy among postmenopausal women.
Design: Observational cohort (1997 to 2003).
Setting: San Francisco Mammography Registry, San Francisco, California.
Participants: Postmenopausal women between the ages of 50 and 74 years without a personal history of breast cancer who underwent mammography (151862 mammograms).
Measurements: Self-reported current use of hormone therapy.
Results: Among menopausal women who had mammography, it was estimated that 41% were currently using hormone therapy in 1997. Before the publication of HERS, the use of hormone therapy was increasing at a rate of 1% (95% CI, 0% to 2%) per quarter. After the publication of HERS, use decreased by 1% (CI, -3% to 0%) per quarter. In contrast, the publication of the WHI in 2002 was associated with a more substantial decline in the use of hormone therapy of 18% (CI, -21% to -16%) per quarter. Similar associations were observed for most subgroups of women, including women older than 65 years of age; women with a previous hysterectomy; and women who described their race or ethnicity as white, African American, Latina, Chinese, or Filipina.
Conclusions: The release of the HERS data was temporally associated with a modest decline in the use of hormone therapy. In contrast, the release of the principal findings from the WHI was associated with a more substantial decline in use by postmenopausal women. The reason for the differences in decline may relate to the fact that the WHI results were widely publicized or were more applicable to most postmenopausal women because the WHI study was performed in healthy women.