OBJECTIVE: To evaluate resting heart rate as an independent predictor of cardiovascular risk in women.

DESIGN: Prospective cohort study.

SETTING: The Women's Health Initiative was undertaken at 40 research clinics in the United States.

PARTICIPANTS: 129 135 postmenopausal women.

MAIN OUTCOME MEASURE: Clinical cardiovascular events.

RESULTS: During a mean of 7.8 (SD 1.6) years of follow up, 2281 women were identified with myocardial infarction or coronary death and 1877 with stroke. We evaluated associations between resting heart rate and cardiovascular events in Cox regression models adjusted for multiple covariates. Higher resting heart rate was independently associated with coronary events (hazard ratio 1.26, 95% confidence interval 1.11 to 1.42 for highest [>76 beats per minute] v lowest quintile [≤62 beats per minute]; P=0.001), but not with stroke. The relation between heart rate and coronary events did not differ between white women and women from other ethnic groups (P for interaction=0.45) or between women with and without diabetes (P for interaction=0.31), but it was stronger in women aged 50-64 at baseline than in those aged 65-79 (P for interaction=0.009).

CONCLUSION: Resting heart rate, a low tech and inexpensive measure of autonomic tone, independently predicts myocardial infarction or coronary death, but not stroke, in women.

TRIAL REGISTRATION: ClinicalTrials.gov NCT00000611.