Modeling Future Projections of Temperature-Related Excess Morbidity Due to Infectious Gastroenteritis Under Climate Change Conditions in Japan

Abstract

Background: Climate change has marked implications for the burden of infectious diseases. We examined temperature-infectious gastroenteritis associations throughout Japan and projected temperature-related morbidity concomitant with climate change for the 2090s. Methods: Daily time series of average temperature and morbidity for infectious gastroenteritis cases in 2005-2015 were collated from the 47 Japanese prefectures. A two-stage time series analysis was adopted to estimate temperature-infectious gastroenteritis relationships. Time series of present and future daily average temperature fluctuations were projected for the four climate change scenarios of representative concentration pathways (RCPs) according to five general circulation models. Excess morbidity for high and low temperatures and the net change in 1990-2099 were projected for each climate change scenario by assuming the absence of adaptation and population alterations. Findings: In 2005-2015, 11,529,833 infectious gastroenteritis cases were reported. There were net reductions in temperature-induced excess morbidity under higher emission scenarios. The net change in 2090-2099 compared to 2010-2019 was -0.3% (95% empirical confidence interval [eCI]: -1.5-0.7) for RCP2.6, -2.4% (95% eCI: -4.7--0.5) for RCP4.5, -3.5% (95% eCI: -6.7-0.1) for RCP6.0, and -6.7% (95% eCI: -11.5--2.9) for RCP8.5. Spatial heterogeneity in the temperature-morbidity relationship was observed among prefectures (Cochran Q test, p<0.001; I2=96.1%). Interpretation: Japan may experience a net reduction in temperature-related excess morbidity due to infectious gastroenteritis in higher emission scenarios. Further projections of specific pathogen-induced infectious gastroenteritis due to climate change are warranted. Funding Statement: This work was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Numbers 15K08714, 16H05247, and 18K11666; and the Medical Research Council UK (Grant ID: MR/M022625/1). Declaration of Interests: The authors have declared that no competing interests exist. Ethics Approval Statement: The contents of this study were approved by the Ethics Committee of the Kyushu University Graduate School of Medical Sciences. Given that this was a retrospective observational study that used national surveillance data and the enrolled subjects were deidentified, there was no need to acquire informed consent.