The impact of clinical trials on the use of hormone replacement therapy. A population-based study.

BACKGROUND

The last 5 years of trial data demonstrate the ineffectiveness of hormone replacement therapy (HRT). The impact of these trials on age-specific HRT use, HRT discontinuation, and regional HRT variation has not been evaluated extensively.

OBJECTIVE

To characterize the relation between HRT trial dissemination and age-specific HRT use, HRT discontinuation, and regional HRT variation before and after the trials' publication.

DESIGN

Using the Medco Health database, we analyzed HRT prescription filling, discontinuation, and regional variation among women > or =55 years from May 1998 to May 2003.

MEASUREMENTS AND MAIN RESULTS

Approximately 340,000 women were eligible for Medco benefits each month. Within 3 months of the Women's Health Initiative (WHI), HRT prescriptions declined from 12.5% to 9.4%, P< or =.0001. When stratified by age, a statistically significant decline in HRT post-WHI occurred in all age groups, with the biggest decline among women > or =55 to 64 (18% to 11%, P< or =.0001). Among HRT users, we found statistically significant increases in discontinuation in 2002 (67%) compared with 2001 (53%, P<.0001). Prior to the WHI there was substantial regional variation in HRT use, with the West South Central and mid-Atlantic having the highest and lowest proportions, respectively (19% vs 6%, P< or =.0001). Despite a relative decline in HRT use of 25% to 42% across all regions, substantial geographic variation remained.

CONCLUSIONS

Hormone replacement therapy use decreased significantly immediately post-WHI, suggesting that trial results can have a rapid effect on practice. Marked regional variation in HRT use persisted after the WHI, suggesting that local practice patterns exert a strong effect on clinical behavior even after new evidence is available.