Association of Heart Rate Variability with Cardiovascular Disease Risk in Healthy Adults

Heart rate variability (HRV) is the variance estimated between each heartbeat and can be utilized to assess autonomic function. The Framingham Risk Assessment (FRA) tool investigates the risk factors associated with cardiovascular disease (CVD) risk, which is a leading cause of mortality in older adults. Previous research has shown that HRV is significantly associated with hypertension risk in hypertensive and normotensive adults. However, the association between HRV and FRA variables is poorly understood in healthy adults. The objective of this study was to explore the relationship between HRV and FRA variables including CVD risk score, hypertension risk and heart age in healthy adults, and if low HRV can serve as an early indicator for CVD risk. We hypothesized that high HRV would be correlated with low CVD risk, low heart age, low hypertension risk. In this retrospective cohort study, we had 38 healthy adults (49.34 ± 19.85 years) including 23 females with body mass index (BMI) of 23.63 ± 4.02 kg/m², waist circumference (WC) of 85.96 ± 10.43 cm, and resting HR (RHR) of 86.47 ± 14.55 bpm. Participants came to the lab one time and wore a Hexoskin smart shirt. Data was collected using 1-lead ECG equipped in the Hexoskin smart shirt (Carre Technologies Inc., Quebec, Canada), which has been demonstrated for both accuracy and reliability in HR measurements. Time-domain variables were studied: SDNN, RMSSD, IBI to measure HRV. Frequency domain variables included ratio of LF/HF to discuss the relationship between sympathetic and parasympathetic activity. These variables were extracted using Kubios HRV analyzer. FRA variables were calculated using the resting blood pressure, age, gender, BMI, previous history of diabetes, hypertension, parental hypertension and smoking. For statistical analysis, we did Pearson’s correlation analysis between time domain variables and FRA variables (CVD risk score, heart age, hypertension risk at 4, 2 and 1 year). For secondary analysis, we looked at correlation between HRV variables and age, BMI, RHR, WC. Also, frequency domain variables correlation with walking and prefrontal cortical (PFC) activation while walking was analyzed. The results of the study showed moderate to high correlation between time domain variables and FRA variables, showing decrease HRV associated with higher CVD risk, higher hypertension risk and higher heart age overall. We also found a decrease in HRV associated with higher age, BMI, RHR, and WC. Lastly, there was moderate correlation between LF/HF and walking, and LF/HF and PFC activation while walking, showing that higher ratio was associated with increase in walking speed and higher PFC activation while walking.