The effects of heat wave warning system on mortality in urban and rural populations in South Korea through 2001-2016

Abstract

Significant threats to public health are posed as climate change is expected to continuously increase global ambient temperature. Many counties have implemented heat wave warning systems to reduce the health impacts of extreme heat but little is known about whether these systems actually reduce heat-related mortality. We assessed changes in the mortality risk of heat waves over time between 2001-2016 in urban and rural regions in South Korea. Mortality, weather monitoring, and air pollution data were collected for 7 urban cities and 8 rural regions. A difference-in-differences analysis combined with propensity score weighting was applied to estimate changes in mortality risks between before and after the implementation of the heat wave warning system (2001-2007, 2008-2016). Results showed evidence of decreased all-cause mortality (-0.611 deaths / 1,000,000 people, 95% CI: -0.974, -0.248) during heat waves in urban populations after the implementation of the warnings. The reduction in mortality was larger in persons aged 65+ (-6.097 deaths / 1,000,000 people, 95% CI: -9.067, -3.127), compared to persons aged 20-64 (-0.715 deaths / 1,000,000 people, 95% CI: -1.101, -0.328). However, decreased mortality was larger in young adult males (age 20-64) than older males, whereas risk reduction in older females was larger than young adult females. Decreased mortality was found for cardiovascular deaths of persons aged 75+ and for respiratory deaths of all-age males. No evidence was found for decreased all-cause mortality in rural populations although decreased mortality was found for respiratory mortality (age 0-19). In conclusion, we found different effects of the national warning system for reducing heat-related mortality among urban and rural populations, which was more effective in urban regions. Further work needs to examine heterogeneity in social resources or perception of high temperature between urban and rural regions that may explain the different mortality effects of heat wave warning system.