Temporal Trends in Outcomes after Out-of-Hospital Cardiac Arrests Witnessed by Emergency Medical Services in Japan: A Population-Based Study

Abstract: Objective: Survival after out-of-hospital cardiac arrests (OHCA) witnessed by emergency medical service (EMS) personnel has been insufficiently understood. The aim of this study was to evaluate temporal trends in survival after EMS-witnessed OHCAs in Japan. Methods: A nationwide, population-based, observational cohort study of consecutive adult OHCA patients with emergency responder resuscitation attempts from January 2005 to December 2012 in Japan. We assessed the trends in annual incidence, characteristics, and outcomes of OHCA patients witnessed by EMS personnel. Multiple logistic regression analysis was used to assess factors that were potentially associated with neurologically favorable outcome defined as cerebral performance category scale 1or 2. Results: During the study period, a total of 66,760 EMS-witnessed OHCAs were documented. The annual incidence rates per 100,000 persons of EMS-witnessed OHCA patients increased from 4.6 (n = 7219) in 2005 to 4.9 (n = 9256) in 2012 (p for trend = 0.035). The proportion of one-month survival with neurologically favorable outcome improved from 5.9% in 2005 to 8.6% in 2012 (p for trend < 0.001), and the proportion increased from 22.1% in 2005 to 30.2% in 2012 in cases with shockable rhythm (p for trend < 0.001). In a multivariate analysis, adults, male gender, shockable rhythm, presumed cardiac origin, and year were associated with a better neurological outcome. Conclusions: In this population, the proportion of one-month survival with neurologically favorable outcome among OHCA patients witnessed by EMS personnel significantly improved during the study period.