Future Projections of Temperature-Related Excess Out-of-Hospital Cardiac Arrest Under Climate Change Scenarios in Japan

Abstract

Background: Recent studies have reported associations between global climate change and mortality. However, future projections of temperature-related out-of-hospital cardiac arrest (OHCA) have not been thoroughly evaluated. Thus, we aimed to project temperature-related morbidity for OHCA concomitant with climate change. Methods: We collected national registry data on all OHCA cases reported in 2005–2015 from all 47 Japanese prefectures. We used a two-stage time series analysis to estimate temperature-OHCA relationships. Time series of current and future daily mean temperature variations were constructed according to four climate change scenarios of representative concentration pathways (RCPs) using five general circulation models. We projected excess morbidity for heat and cold and the net change in 1990–2099 for each climate change scenario using the assumption of no adaptation or population changes. Findings: During the study period, 739,717 OHCAs of presumed cardiac origin were reported. Net decreases in temperature-related excess morbidity were observed under higher emission scenarios. The net change in 2090–2099 compared with 2010–2019 was -0.8% (95% empirical confidence interval [eCI]: -1.9–0.1) for RCP2.6, -2.6% (95% eCI: -4.4–-0.8) for RCP4.5, -3.4% (95% eCI: -5.7–-1.0) for RCP6.0, and -4.2% (95% eCI: -8.3–-0.1) for RCP8.5. Interpretation: Our study indicates that Japan is projected to experience a substantial net reduction in OHCAs in higher-emission scenarios. The decrease in risk is limited to a specific morbidity cause, and a broader assessment within climate change scenarios should consider other direct and indirect impacts. Funding Statement: The Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Numbers 15K08714, 16H05247, and 18K11666; the Medical Research Council UK (Grant ID: MR/M022625/1). Declaration of Interests: We declare no competing interests. Ethics Approval Statement: This study was approved by the Ethics Committee of the Kyushu University Graduate School of Medical Sciences. Written informed consent was not required because of the retrospective observational nature of this study, which used national registry data, and the fact that enrolled subjects were deidentified by the Fire and Disaster Management Agency (FDMA).