Rhythm-Specific Regional Variation in Neurological Outcomes After Out-of-Hospital Cardiac Arrest: A Nationwide Registry Study in Japan

Background Regional variation in outcomes after out-of-hospital cardiac arrest (OHCA) has been reported worldwide; however, whether its magnitude differs by initial cardiac rhythm remains unknown. This study aimed to evaluate prefecture-level variation in neurological outcomes after OHCA according to initial cardiac rhythm. Methods This retrospective observational study included adult patients with atraumatic OHCA registered in the All-Japan Utstein Registry from 2019 to 2023. Patients were categorized as presenting with a shockable rhythm, pulseless electrical activity (PEA), or asystole according to the initial cardiac rhythm. Mixed-effects logistic regression models were fitted separately for each rhythm group, with favorable neurological outcome at 1 month (defined as a Cerebral Performance Category of 1–2) as the dependent variable and prefecture as a random effect. Prefecture-level variation was quantified using the median odds ratios (MORs). Results Among 616,519 participants, 46,575 had a shockable rhythm, 142,073 had PEA, and 427,871 had asystole. Favorable neurological outcomes occurred in 22.3%, 2.7%, and 0.2% of patients, respectively. The MORs were 1.19 for shockable rhythm, 1.31 for PEA, and 1.65 for asystole, indicating progressively greater prefecture-level variation across rhythm categories. Conclusions The magnitude of prefecture-level variation in favorable neurological outcomes differed by initial cardiac rhythm categories and was greatest among patients with asystole. The mechanisms underlying these regional differences remain unclear. Future investigations of regional and healthcare system characteristics may help identify potentially modifiable factors associated with disparities in OHCA outcomes.