Association between Daily Temperature Variability and Short-term Mortality in 6 Taiwan Major Cities

Abstract

Background:Previous studies have evidenced that temperature and extreme weather (e.g. heat waves) are associated with increased risks of mortality. However, only limited studies focused on the temperature variability and its impacts on human health. Given the facts that climate change is predicted to increase the temperature variation, it becomes imperative to explore the role of temperature variability on human adverse effects. Aims:Assess the association between daily temperature difference (maximum temperature subtracted by minimum temperature) and short-term mortality. Methods:Death certification and meteorological data in 6 Taiwan major cities from 1994-2008 were extracted from Central Weather Bureau and Department of Health. Monitoring record of air pollutants was obtained from Taiwan Environmental Protection Administration. A two-stage time-series analysis was performed to assess the association between daily temperature difference and mortality. Poisson regression models were used to estimate city-specific relative risks of mortality associated with daily temperature difference. Random effect relative risks were reported for the national-wide estimate of the association between daily temperature difference and mortality. Results:1 degree (Celsius) increase in daily temperature difference was significantly associated with daily mortality (relative risk [RR], 1.007; 95% confidence intervals [CIs], 1.003 - 1.012). Results were robust to adjustment for ozone, particulate matter, and degree of freedom for time variables. Additionally, this positive association was also observed on cardiovascular mortality (RR, 1.004; 95% CIs, 0.997 – 1.011) and respiratory mortality (RR, 1.006; 95%CIs, 0.996 – 1.017) although they did not reach the statistical significance. Conclusions:Daily temperature variation is associated with elevated risks of mortality. These results suggest that under the scenario of climate change, public health professional may take precautionary actions to reduce adverse health effects attributable to temperature variability.