Evaluation of two easy-to-implement digital breathing interventions in the context of daily stress levels in a series of N-of-1 trials: results from the Anti-Stress Intervention Among Physicians (ASIP) study.

Physicians face intense work-related stress, which can harm their health, increase the risk of medical errors, lower healthcare quality, and increase costs within the healthcare system. In this 4-week intervention study, individual-level and population-level effects of two short and easy-to-perform breathing exercises designed to reduce stress are evaluated among 76 physicians in residency in Germany in a series of N-of-1 trials. Levels of stress and levels of stress expected for the following day were assessed electronically every day via the StudyU App (protocol adherence: 91.9%). Average intervention effects were estimated using Bayesian linear regression models. They were overall small on the population level, but they showed large heterogeneity between individuals, with strong effects for selected individuals, with stress reduction of up to 3 points on a 1 to 10 stress scale. Thirty-one participants benefited from the anti-stress exercises. Three (mindfulness breathing) and seven participants (box breathing) had a ≥70% probability for a daily stress reduction of ≥0.5 points and thereby fulfilled our responder criteria. Of the 17 participants who completed the follow-up survey about 4.5 months after completion of the individual N-of-1 trials, 58% reported that they felt they had benefited from the intervention and 42% planned to use it in the future. The results highlight the value of personalized perspectives: while the studied interventions showed only small positive benefits for the "average person", they may well help actual individual persons, here 10 of 76 or even 31 of 76 participants.