1000 Days of HRV: A Case Study of Daily Post-Wake-Up Heart Rate Variability for Tracking Stressful Life Events

Longitudinal monitoring of heart rate variability (HRV) can offer deep insight into an individualized physiological trajectory of responding to stressful events. The current single-participant longitudinal case study (male, 26 to 29 years; N = 1) reports 1,000 days of post-wake-up resting-state HRV recordings, complemented by 878 nights of nocturnal HRV and 142 diary entries documenting noteworthy events. The study examined (1) whether daily post-wake-up HRV can identify meaningful within-person physiological deviations that correspond to naturally occurring stressful periods or impactful events, (2) whether shorter 1-minute recordings are equally informative compared with full 2-minute recordings, and (3) how post-wake-up and nocturnal HRV relate. Thirteen downward deviations from the typical range were identified, most of which corresponded to meaningful contextual life events. The largest reduction in HRV occurred during a period of exposure to a war zone, concurrent respiratory illness, and bereavement. Other pronounced HRV suppressions were observed during psychologically stressful periods or medical conditions, including two benign paroxysmal positional vertigo episodes. RMSSD derived from 1-minute versus 2-minute recordings showed close agreement (r = .92, p < .001), suggesting that shorter recordings may provide similar information. In contrast, post-wake-up and nocturnal RMSSD showed only modest correspondence (r = .35, p < .001), with nocturnal HRV appearing less sensitive to contextual changes. These findings suggest that a brief, standardized post-wake-up HRV protocol can feasibly capture meaningful day-to-day physiological dynamics in everyday life, relative to one’s own typical range, helping investigate individualized trajectories of stress response, recovery, and adaptation.