Rationale: Lower heart rate variability (HRV) has been associated with increased all-cause mortality and adverse cardiovascular events including sudden death. The role of HRV in post-menopausal women is understudied. Therefore, we tested the hypothesis of a significant association between HRV and incident coronary heart disease (CHD) and CHD death in post-menopausal women.
Methods: This is an analysis of prospective data collected during the Women’s Health Initiative (WHI) clinical trials. A total of 57,061 post-menopausal women were included. HRV was quantified using two variables; standard deviation of all normal-to-normal RR intervals (SDNN, milliseconds), and the root mean square of successive differences in normal-to-normal RR intervals (RMSSD, milliseconds). We used Cox proportional hazards models to test the association between HRV and incident CHD, hard CHD (including myocardial infarction and fatal CHD), and total CHD death. We controlled for age, race, alcohol use, physical activity, depression, BMI, smoking, diabetes, hypertension, lipid disorders, and family history of CHD.
Results: The results are as highlighted for incident and hard CHD in table 1 and for CHD death in table 2. There were statistically significant associations between lower HRV (as a continuous variable and as quartiles) and higher levels of incident CHD.
Conclusion: In post-menopausal women, lower HRV was associated with a modestly higher, but statistically significant, risk for incident cardiovascular events, including fatal and non-fatal myocardial infarction. Factors associated with lower HRV and cardiac autonomic impairment may be candidates for reducing CHD risk, such as better glycemic control and improved physical activity.