Coronary heart disease events in the Women's Health Initiative hormone trials: effect modification by metabolic syndrome: a nested case-control study within the Women's Health Initiative randomized clinical trials

Abstract

Objective: Our objective was to determine whether metabolic syndrome (MetS) or its components modified the effect of hormone therapy (HT) on the risk of coronary heart disease (CHD) events in the Women's Health Initiative clinical trials.

Methods: We performed a nested case-control study of incident CHD events during the first 4 years of follow-up in the Women's Health Initiative HT trials (estrogen plus progestin therapy [EPT] and estrogen therapy [ET]). There were 359 incident cases of CHD during follow-up. After the exclusion of women with cardiovascular disease (n = 90), diabetes, or hypertension at baseline (n = 103), 166 CHD cases were matched to 524 controls on age, randomization date, and hysterectomy status. MetS classification required at least three of five Adult Treatment Panel III criteria. Analyses by χ and t tests for heterogeneity and logistic regression were performed. Postmenopausal women (n = 27,347) aged 50 to 79 years from 40 US clinical centers participated. Daily conjugated equine estrogens (0.625 mg) and medroxyprogesterone acetate (2.5 mg; EPT) or conjugated equine estrogens (0.625 mg; ET) were compared with placebo. The main outcome measure was the odds for CHD with HT use versus placebo by MetS status.

Results: MetS modified the risk of CHD events with HT. In the pooled analysis, risk was increased with HT versus placebo in women with MetS (odds ratio, 2.26; 95% CI, 1.26-4.07), whereas women without MetS were not found to have an increased risk for a CHD event with HT (odds ratio, 0.97; 95% CI, 0.58-1.61; P for interaction = 0.03). Results of the EPT and ET trials, when examined separately, were similar. The constellation of MetS variables was more predictive of risk from HT than MetS components assessed individually. When women with diabetes or hypertension were included in the analysis, statistically significant effect modification was not detected.

Conclusions: MetS at baseline in women without prior cardiovascular disease, diabetes, or hypertension at baseline identifies women who are more likely to have had adverse coronary outcomes on HT. CHD risk stratification is recommended before initiating HT. The basis for the greater risk of CHD events with HT among women with MetS requires further study.