Ambient temperature and injury-related deaths in Japan from 1979 to 2015

Abstract

BACKGROUND AND AIM: Although substantial evidence suggested that high and low temperatures were adversely associated with non-accidental mortality, limited studies have focused on exploring the adverse impacts of ambient temperature on injury-related deaths. In this study, we aimed to investigate the short-term associations for all and cause-specific injury deaths in all 47 prefectures of Japan from 1979 to 2015. METHODS: We conducted a two-stage meta-regression analysis. First, we performed the prefecture-specific time-stratified case-crossover analyses to examine the association between temperature and all and four selected causes of injury deaths (suicide, transport accident, falls, and drowning). Then, we used a multivariate meta-regression model to combine the effect estimates across all prefectures in Japan. RESULTS:A total of 2,416,707 injury deaths were included in this study. We found a J-shaped association curve for total injury deaths, in which the risks increased for mild cold (the 34th percentile; RR=1.04, 95%= 1.02, 1.07) and extremely hot (the 99th percentile; RR=1.33, 95%= 1.28, 1.39), compared to the risk at the 70th percentile of temperature, respectively. However, the shapes of the association curves varied depending on the cause-specific injury deaths. For example, we found that the risks for suicide and transport accidents monotonically increased as temperature increases, while the J- or U-shaped association curves were estimated for falls and drowning. CONCLUSIONS:Both low and high temperature may be important drivers of increased risk of injury deaths. We suggest that preventive measures against injury deaths in conjunction with non-accidental mortality need to be considered in climate change adaptation policies in Japan. KEYWORDS: Temperature, Mortality, Epidemiology