Temperature, Air Pollution, and Cardiopulmonary Diseases: A Multi-City Analysis of Morbidity and Mortality in Japan

This study investigated the effects of temperature, as well as extreme temperature events and air pollution on cardiovascular and respiratory morbidity and mortality in Tokyo's 23 wards, Osaka city, and Nagoya city from 2017 to 2019. We utilized a two-stage time-series analysis to explore daily average temperature, extreme temperature events with different percentile and air pollutant concentrations (NO _x , CO, SO₂, PM_2.5, suspended particulate matter [SPM]), and health outcomes. Results showed that low temperatures significantly increased cardiovascular and respiratory disease risks, with effects more pronounced than those of high temperatures. The minimum mortality temperature was approximately 12-15 °C for mortality of respiratory and cardiovascular disease. Extreme cold event (at 2.5th and fifth percentiles) consistently increased morbidity and mortality risks of respiratory disease and mortality of cardiovascular disease, while Extreme heat event effects were less pronounced and occasionally increased the risk of mortality from cardiovascular and respiratory diseases (at the 95th and 97th percentiles). All air pollutants demonstrated immediate effects (lag0-1 days) on cardiovascular and respiratory disease morbidity. PM_2.5 and SPM exhibited more prolonged impacts on cardiovascular morbidity. This study provides insights into the distinct health impacts of temperature, extreme temperature events, and air pollution in Japan's urban areas, highlighting the need for targeted public health interventions considering both environmental stressors.