High resting heart rate and low heart rate variability – both indicators of autonomic imbalance – can predict some elements of metabolic syndrome, according to findings derived from the Framingham Heart Study offspring cohort.
In that cohort (n = 1,882), both high resting heart rate (RHR) and low heart rate variability (HRV) at baseline were significant predictors of high blood pressure, hyperglycemia, and a diagnosis of diabetes within 12 years. The research points to the potential usefulness of autonomic imbalance measures in interventional and epidemiologic studies, according to Dr. Lawson R. Wulsin of Cincinnati Veterans Affairs Medical Center and University of Cincinnati and his associates (J. Clin. Endocrinol. Metab. 2015 [doi:10.1210/jc.2014-4123]).
The investigators sought to determine any links between RHR, HRV, and any of five key measures of metabolic syndrome: elevated triglycerides, low high-density lipoprotein cholesterol (HDL-C), elevated blood pressure, elevated fasting glucose, and body mass index. Low HRV, along with age, sex, and smoking status, predicted high blood pressure (P= .0002) and hyperglycemia (P= .0015), while elevated RHR was significantly predictive of high blood pressure (P< .0001) and hyperglycemia (P= .0013) along with the other risk factors. HRV also predicted incident diabetes along with smoking, age, and sex (odds ratio, 0.549; 95% confidence interval, 0.429-0.701; P < .0001) as did RHR (OR, 1.638; 95% CI, 1.364-1.966; P < .0001).
Dr. Wulsin and his colleagues noted in their analysis that they could not explain why the two indicators of autonomic imbalance were better predictors of high blood pressure and hyperglycemia than were the three other outcome measures used in the study. “It is possible that in our sample, lipids were more influenced by insulin resistance or some other factor than by autonomic activity,” they wrote. Dr. Wulsin and his colleagues noted as the weaknesses of their study its use of a mostly white and middle-class cohort, and that the duration of autonomic imbalance was not captured, nor were other potential variables including physical activity, inflammation, and insulin resistance.
The study was funded by the Department of Veterans Affairs; none of its authors reported conflicts of interest.