Normative Values of Heart Rate Variability During Sleep in Indian Population

Heart rate variability (HRV) measurement is a noninvasive method to assess the autonomic nervous system. Therefore, conducting HRV measurements to asses many risk factors including cardiovascular is gaining popularity in athletic, non-athletic, and clinical populations. An electrocardiogram (ECG) is the most reliable tool to measure HRV, but using heart rate monitors like wristbands, watches, and chest bands are more useful during ambulatory or fitness-related activities. Studies have been conducted for the wake time HRV in various populations, but HRV measurements during sleep have not been conducted yet. The time domain of HRV quantifies the amount of variability in measurements of the inter-beat interval (IBI), which is the time period between successive heartbeats. This study analyzed time-domain sleep HRV in a large sample (n = 300) of a healthy young population. ECG of subjects were recorded during sleep using the Repose chest wearable. The ECG was preprocessed and analysed by Repose platform. Kubios standard software (version 3.5) was used to measure the sleep time HRV parameters. It was found that the HRV for 15-minute deep sleep window can reliably give a baseline data against which wake time HRV can be compared. It was also found that males have significantly (p<0.05) higher HRV compared to females. In conclusion, this study provided normative data for sleep time-domain HRV parameters and also reflected that females have higher sympathetic activity compared to males in the Indian population. These values will help compare the clinically or otherwise measured HRV to the benchmarks established by the study.