Time-Regular Pattern Analysis on Effect of Extreme Temperature to the Death of Cerebrovascular and Cardiovascular Diseases in Chongqing

Objectives To examine the association between extremely cold and hot temperature with mortality of cerebrovascular and cardiovascular diseases and their time-patterns in one of the unbearably hot city Chongqing in China.

Methods The data of cerebrovascular and cardiovascular mortality, meteorology and air pollution in 2011-2013 in Chongqing were collected. A distributed lag non-linear model (DLNM) was used to investigate the lag effect and the cumulative effect of extremely cold and hot temperature on mortality for lag (0~30) days, considering with air pollutants and short-term and long-term time trends as possible confounding factors.

Results The effect of extremely high temperature on the mortality of cerebrovascular diseases lasted for two days (lag 0-1) with a peak RR (1.66, 95%CI:1.19~2.33) at the day (lag 0); the effect of cold delayed by four days and lasted for twelve days (lag 4~15), with the highest risk (RR=1.22, 95%CI:1.06~1.41) at the sixth day (lag 6). The effect of extremely high temperature on the mortality of cardiovascular diseases lasted for seven days with a peak RR (1.88, 95%CI:1.12~3.15) at the day (lag 0); the effect of extremely low temperature delayed by one day and lasted for twenty-seven days, with the highest risk (RR=2.05, 95%CI:1.32~3.20)at the second day (lag 2). The cumulative relative risk of extremely high temperature (34℃) on the mortality of cerebrovascular and cardiovascular diseases were 2.08 (95%CI:1.49~2.90) and 2.63 (95%CI:1.27~5.42), respectively; the cumulative relative risk of extremely low temperature (2℃) on the mortality of cerebrovascular and cardiovascular diseases were 4.61 (95%CI:1.85~11.5) and 120 (95%CI:3.72~463), respectively.

Conclusions Both extremely cold and hot temperature increased the mortality of cerebrovascular and cardiovascular diseases with different patterns in Chongqing. The cumulative effect of extremely low temperature was higher than that of extremely high temperature on the mortality of cerebrovascular and cardiovascular diseases, especially on cardiovascular diseases.