Association between extreme ambient temperature and onset of ischemic stroke: Time series study in Wuhan and Yichang, China

Abstract There is no consensus in previous studies on the association between ischemic stroke (IS) and extreme ambient temperature. Few studies have explored the effects of extreme ambient temperature on different etiologies of IS. We collected 3079 IS cases from two stroke centers in Central China (Wuhan and Yichang cities) continuously from January 1, 2016 to December 31, 2017, meteorological data and pollutant data published by China Meteorological Data Network for the same period. According to the Trial of ORG 10172 in Acute Stroke Treatment (TOAST), IS cases were divided into large artery atherosclerosis (LAA), cardioembolism (CE), small artery occlusion (SAO), and stroke of other etiology (SOE). Distributed lag nonlinear models of time series analysis were used to explore the association between extreme ambient temperature and the onset of IS and its etiology subtypes after controlling for potential covariates. By comparing single-day relative risk (RR) with 95% confidence interval (CI), extreme ambient temperature did not increase the onset of total IS, SAO or SOE; extreme cold temperature increased the onset of LAA (RR =1.70,95%, CI =1.04–2.75, threshold = 3.5 °C, log = 2) and CE (RR =2.96,95%, CI = 1.05–8.39, threshold = 2.2 °C, log = 0; RR =2.92,95%, CI =1.11–7.71, threshold = 3.5 °C, log = 0). The overall cumulative association between ambient temperature and the onset of LAA and SOE was statistically significant. There was no association between extreme temperature and total IS. Extreme cold temperature is a risk factor for the onset of LAA and CE.