18-year trends in outcome and resuscitation process of out-of-hospital cardiac arrest by time of day

Background Out-of-hospital cardiac arrest (OHCA) remains a major public health challenge, with nighttime and off-hours consistently associated with worse outcomes. However, whether these temporal disparities have improved over time remains unclear. Methods This nationwide, population-based cohort study used data from the All-Japan Utstein Registry (2005–2022). Patients with witnessed cardiac arrest of presumed cardiac origin who received cardiopulmonary resuscitation (CPR) from emergency medical services were included. The exposure of interest was the time of cardiac arrest onset (categorized into 3- and 1-hour intervals) and calendar year. The primary outcome was 30-day survival with good neurological status (Cerebral Performance Category scores 1 or 2). Secondary outcomes included overall 30-day survival, prehospital resuscitation behaviors including bystander-initiated CPR, and time-related outcomes (e.g., intervals from collapse to hospital arrival). Temporal trends were evaluated using crude and age-adjusted logistic regression models. Results Of 403,873 patients (median age, 78.0 years; 61.4% male), time-of-day disparities in good neurological outcomes persisted in 2019–2022, with the age-adjusted proportion highest during daytime (11:00–12:00, 8.2%; 95% CI, 7.4%–8.9%) and lowest during nighttime (1:00–2:00, 3.3%; 2.6%–4.0%) (Figure 1). The age-adjusted proportion of good neurological outcome improved across all time categories (e.g., from 1.4%–2.9% in 2005 to 2.3%–5.9% in 2022; all P for trends < 0.001). However, segmented regression identified an inflection point in 2016 (Davies test, P < 0.001), after which improvement plateaued (Figure 2). The age-adjusted proportion of bystander CPR increased from 34.3%–41.1% in 2005 to 51.5%–60.9% in 2022 across all time categories, while the age-adjusted mean interval from collapse to hospital arrival increased by approximately 4–6 minutes across all time categories (all P for trends < 0.001). Conclusions In this nationwide OHCA registry in Japan, neurological outcomes improved across all time-of-day categories over eighteen years, but improvement has recently plateaued. Despite absolute improvements, relative temporal disparities persisted, with nighttime outcomes remaining inferior to daytime. These findings underscore the urgent need for system-wide strategies to optimize 24-hour resuscitation systems and mitigate vulnerabilities in off-hours care.Figure1Figure2