Letters Section Editor: Robert M. Golub, MD, Senior Editor.
To the Editor: Dr Rossouw and colleagues1 conclude that use of estrogen among women aged 50 to 59 years may not increase CHD risk, based on combined data from the CEE and CEE + MPA trials of the WHI. However, temporal trends in the use of hormone therapy may complicate the interpretation of their data.
From the early 1980s to the mid-1990s, the prevalence of hormone therapy use among postmenopausal women in the United States increased significantly to approximately 30% among women aged 60 to 74 years and 47% among women aged 50 to 59 years.2,3 In general, women receiving hormone therapy who subsequently developed breast cancer or venous thromboembolism would have been taken off this therapy permanently and would not have entered WHI, thus creating a “survivor effect” among previous hormone therapy users who did enter the trial. A hormone therapy survivor effect has been noted in previous analyses4 and is possibly reflected in the reduced HRs for CHD, breast cancer, and venous thromboembolism found in the CEE only compared with the CEE + MPA trial, since women in the CEE trial were twice as likely to have been prior hormone therapy users.5 With the greater use of hormone therapy in the years shortly before WHI, a survivor effect would be more pronounced among younger women and would differentially affect the CEE and CEE + MPA groups if hormone therapy is harmful, thus either creating or exaggerating a trend of increasing HRs from younger to older women in the combined data analysis.
Shaffer LET, Krantz CA. Hormone Therapy and Cardiovascular Risk. JAMA. 2007;298(6):623-625. doi:10.1001/jama.298.6.623-b