Nonlinear Association between summer high Temperature and Mortality in people aged 65 or more: Past and Recent periods

Abstract

BACKGROUND AND AIM: Climate change induces extreme weather including frequent heat waves in summer. We aimed to examine how the impact of high air temperature exposure to mortality of older people, a vulnerable group, has been changed from the past to recent periods. METHODS: Temperature data from the Korea Meteorological Administration and mortality data from Statistics Korea were used. The time-series analysis was performed for the periods 1991–1995 and 2015–2019, in which included the recorded heat wave. We used the distributed lag non-linear models (DLNM) to estimate cumulative relative risks (CRRs) to see an association between daily temperature for July to August and mortality of people aged 65 or more. The CRR was estimated at each province and pooled the CRRs of all provinces using a random effect meta-analysis. RESULTS: The CRRs on mortality of the daily mean temperature in summer for the population aged 65 or more for the whole 10-year period (1991-1995 and 2015-2019) were 1.098 (1.012, 1.192), 1.124 (1.027, 1.231), and 1.172 (0.986, 1.392) at 90%tile, 95%tile, and 99%tile, compared to 50%tile of the temperature. When the nonlinear associations between temperature and mortality were plotted in the past and recent periods separately, the CRR in the past increased substantially with temperature increases, while the increase of CRR in the recent appeared to be relatively small. CONCLUSIONS: The effects of high temperatures in summer on mortality of people aged 65 or more have changed from the past to recent periods, and further studies are needed to explore factors potentially related with resilience of the society against climate change.