Diurnal Temperature Range is a Risk Factor for Coronary Heart Disease Death

Jingyan Cao,Cheng Jiang,Ni Zhao,Renjie Chen,Weimin Song,Haidong Kan,Yuexin Cheng

doi:10.2188/jea.je20080074

Abstract

BackgroundAlthough the relation between day-to-day temperature change and coronary heart disease (CHD) mortality is well established, it is unknown whether temperature variation within 1 day, ie, diurnal temperature range (DTR), is an independent risk factor for acute CHD death.MethodsWe used time-series and case-crossover approaches to assess the relation between DTR and daily CHD mortality between 2001 and 2004 in Shanghai, China. Specifically, we used exposures averaged over periods varying from 1 to 5 days to assess the effects of DTR on CHD mortality. We estimated the percent increase in the number of daily deaths related to CHD that were associated with DTR, after adjustment for daily meteorologic conditions (temperature and relative humidity) and levels of outdoor air pollutants.ResultsBoth time-series and case-crossover analyses showed that DTR was significantly associated with the number of daily deaths related to CHD. A 1 °C increase in 2-day lagged DTR corresponded to a 2.46% (95% CI, 1.76% to 3.16%) increase in CHD mortality on time-series analysis, a 3.21% (95% CI, 2.23% to 4.19%) increase on unidirectional case-crossover analysis, and a 2.13% (95% CI, 1.04% to 3.22%) increase on bidirectional case-crossover analysis.ConclusionsOur findings suggest that DTR is an independent risk factor for acute CHD death.

Highlights

Coronary heart disease (CHD) is a common cause of death and a leading cause of severe long-term disability in developed countries and some developing countries
In both time-series and case-crossover analyses, we found a statistically significant association between diurnal temperature range (DTR) and the daily number of deaths related to coronary heart disease (CHD), after adjustment for long-term and seasonal trends in CHD mortality, days of the week (DOW), temperature, relative humidity, and concentrations of air pollutants
Evidence from this study shows that temperature variation within 1 day—DTR—is associated with the CHD mortality

Summary

INTRODUCTION

Coronary heart disease (CHD) is a common cause of death and a leading cause of severe long-term disability in developed countries and some developing countries. Despite widespread concern and the great health burden imposed on middle-aged and elderly persons, associations between CHD and environmental risk factors have not been studied adequately. The relation varies with weather pattern, latitude, air pollution levels, and the prevalence of air-conditioning systems.[6]. Diurnal temperature range (DTR) is defined as the difference between the maximum and minimum temperatures in 1 day. A relation between temperature and CHD mortality has been observed,[3,4,5] it is not known whether DTR is a risk factor for acute CHD death independent of the corresponding temperature. We hypothesized that a large DTR results in additional environmental stress to the human cardiovascular system, thereby increasing the risk for acute CHD death. We used time-series and case-crossover analyses of daily weather and mortality data from Shanghai, China to test our hypothesis

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DISCUSSION