Triggered by the Heart: Effectiveness of Two Brief Just in Time Adaptive Interventions (JITAI) for Reducing Stress and Stabilizing Cardiac Autonomic Function (Preprint)

Abstract

BACKGROUND Transient heart rate variability decreases independent of bodily movement (additional heart rate variability reductions; AddHRVr) potentially reflect moments of psychophysiological vulnerability. OBJECTIVE We applied this measure by means of wearables in everyday life to trigger low-threshold 1-min interventions with the aim to stabilize autonomic function and relieve perceived stress and ruminative thoughts. METHODS In two pre-registered micro-randomized trials participants underwent a 1-day calibration period to derive individualized trigger settings, and then received AddHRVr-triggered and random prompts throughout the following 3 days asking for perceived stress and rumination. In Study 1, N = 60 participants underwent a slow breathing intervention (0.1 Hz resonance breathing) following each prompt and in Study 2, N = 49 participants were micro-randomized to an external attention and mindful breathing intervention, respectively. RESULTS Following interventions in both studies, perceived stress and ruminative thoughts significantly declined irrespective of the kind of prompt and intervention. AddHRVr-triggered prompts resulted in a stronger increase in HRV during the slow-paced breathing and mindful breathing interventions and elevated HRV in a time frame of 10 minutes following the interventions (in contrast to random prompts). CONCLUSIONS Both studies show for the very first time that an AddHRVr algorithm can be used to trigger brief just in time interventions by wearables to stabilize autonomic function, thus potentially promoting cardiac health.