Observational evidence largely supported the use of hormone therapy (estrogen plus progestin (EPT) and estrogen-alone (ET) for chronic disease prevention. In July 2002, the Women's Health Initiative (WHI) released the news that its Data and Safety Monitoring Board terminated the EPT randomized trial early because the risks outweighed the benefits.

We obtained NCI funding to examine the diffusion of the WHI's results into clinical practice. Data was gathered on overall and agespecific EPT and ET prevalence, along with discontinuation and initiation rates in the two years before the published results of WHI's EPT trial, and for five months after their release. Our observational cohort study worked in collaboration with the 10-site HMO Center for Education and Research on Therapeutics (CERT) Patient Safety Cohort.

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We extended the period of observation for the Patient Safety Cohort (originally 1/1/1999 - 6/30/2001) through December 31, 2002. From the original sample, we constructed a dynamic cohort of 169,586 women 40-80 years from GHC, HPHC, Fallon, KPCO, and HealthPartners. We defined EPT users as women who received combination products or estrogen preparations with >=1 dispensing for a progesterone product. ET users included women who received estrogen preparations with no progesterone dispensing. We considered women to be continuous users as long as the hormones were dispensed within 60 days of the run-out date. A new run-out date was set with each successive dispensing rather than using cumulative number of pills from all dispensings.

Despite our necessary lag-time, we found an immediate reduction in EPT and ET use following July 2002. The overall prevalence of hormone use was 27.2% at baseline; 14.6% EPT and 12.6% ET. We found a 45.9% and a 27.8% reduction in EPT and ET prevalence, respectively, after July 2002. We also saw a reduction in the proportion of users who filled prescriptions for >=0.625 mg of conjugated equine estrogen or its equivalence (43.7% and 18.9% decrease in the prevalence of 0.625 mg and >0.625 mg conjugated equine estrogen [CEE], respectively) and an increase in users of 5.8% in <0.625 mg. These findings are supported by self-reported data from other cohorts and national pharmacy sales.

The evidence from WHI's EPT trial has made it increasingly clear that the risks of using EPT outweigh the benefits for women without menopausal symptoms. There is still substantial EPT use among women who are likely not using EPT for short-term therapy for the relief of menopausal symptoms. Long-term EPT use has important public health consequences. Further exploration of why women continue to use EPT and identification of alternative methods for addressing reasons for continued use are indicated.

We do not yet know whether improving knowledge of the risks and benefits of hormone replacement therapy would further decrease its use. However, as of July 2004, Katherine Newton (GHC) and Maureen Connelly (HPHC) are collaborating on a study to further explore womenlevel decisions about using hormone therapy. There is also an effort to increase follow-up from this current study through 2003 to examine how the trends of hormone use have changed with the additional WHI publications and to explore the uptake of other alternative medications for chronic disease prevention.

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