Decreased long term variations of heart rate variability in subjects with higher self reporting stress scores

Heart rate variability (HRV) has been well established to measure instantaneous levels of mental stress. Circadian patterns of HRV features have been reported but their relationships to mental stress were not studied explicitly for estimating stress levels. In this study, we investigated long term variations of HRV features to provide a reliable measure of chronic stress levels. Twenty three subjects were divided into high (n = 10) and low stress group (n = 13) depending their self reporting stress scores. HRV features were calculated during five different time periods of the day. High stress group showed decreased overall variations of HRV features but similar median values to low stress group. Compared to normal sinus rhythm data during each time period, high stress group showed significantly less % difference of HRV patterns than low stress group. Our data suggested that long term variations of HRV features might be more useful to detect subjects under chronic stress.