Age-specific effects of hormone therapy use on overall mortality and ischemic heart disease mortality among women in the California Teachers Study

Objective: Although the Women's Health Initiative trial suggested that menopausal hormone therapy (HT) does not reduce coronary heart disease mortality overall, subsequent results have suggested that there may be a benefit in younger women. The California Teachers Study questionnaire and mortality data were used to examine whether age modified the association between HT and the relative risk of overall mortality and ischemic heart disease deaths. Methods: Participants from the California Teachers Study were 71,237 postmenopausal women (mean age, 63 y; range, 36-94 y) followed prospectively for mortality and other outcomes from 1995-1996 through 2004. Results: Age at baseline was a much more important modifier of HT effects than was age at start of therapy. Risks for all-cause mortality (n = 8,399) were lower for younger current HT users at baseline than for never users (for women <= 60 y: hazard ratio, 0.54; 95% CI, 0.46-0.62). These risk reductions greatly diminished, in a roughly linear fashion, with increasing baseline age (for women 85-94 y: hazard ratio, 0.94; 95% CI, 0.81-1.10 for all-cause mortality). Similar results were seen for ischemic heart disease deaths (n = 1,464). No additional significant modifying effects of age at first use, duration of use, or formulation were apparent. Conclusions: These results provide evidence that reduced risks of mortality associated with HT use are observed among younger users but not for older postmenopausal women, even those starting therapy close to their time of menopause.