| Objective:The aim of this study is to evaluate the lag and cumulative effect of air pollutants on the incidence of ischemic stroke in Shenzhen in different seasons and temperature environment,and further compare such effect in different seasons and temperature environment.Methods:This research includes daily new cases of ischemic stroke,meteorological factors,ambient air pollutants and other data in Shenzhen from January 1,2008 to December 31.Using the distributed-lag linear model,the effect of air pollutants on the incidence of ischemic stroke in different seasons is analyzed.Furthermore,a generalized additive model that combined with stratification parametric analysis were used to evaluate the difference in the effect of air pollutants on the incidence of ischemic stroke at different temperature levels.Finally,the interaction effect between air pollutants and ambient temperature is visualized through the method of response surface.Results:1.In 2008-2014,there were 63,997 new cases of ischemic stroke in adults（≥the age of 18）collected in Shenzhen,in which 38,070 cases were male patients,and25,927 female.In addition,in 2008-2014,the number of new cases in adults（≥the age of 18）in Shenzhen showed an upward trend year by year,in which the proportion of the young and middle-aged groups（the age of 18-64）was on the rise.In all new cases in adults（≥the age of 18）,the elderly（≥the age of 65）contributed 31,000 cases,accounting for 48.44%;the young and middle-aged groups（18-64 in age）contributed 32,997 cases,accounting for 51.56%.The average age was 63.41.2.According to results of the single-pollutant model,NO2,SO2 and PM10significantly affected incidence of ischemic stroke.For every 10μg/m3 increased in the concentration of NO2,SO2 and PM10,the percentage increment and 95%confidence interval of ischemic stroke incidence（cumulative lag of 12 days）were 3.68%（1.76%-5.63%）,10.27%（4.83-15.99%）and 1.42%（0.40%-2.44%）,respectively.3.According to seasonal stratification analysis,the effects of NO2,PM10 and SO2 on ischemic stroke incidence showed a seasonal pattern,i.e.significant in winter but statistically insignificant in summer.In winter,for every 10μg/m3 increased in the concentration of NO2,SO2 and PM10,the percentage increment and 95%confidence interval of ischemic stroke incidence（cumulative lag of 12 days）were 4.32%（1.75%-6.95%）,1.60%（0.19%-3.04%）,13.74%（6.35%-21.63%）,respectively.The result of inter-layer Z-test showed that the adverse health effect of NO2 on ischemic stroke was stronger in winter than in summer.4.According to temperature stratification analysis,the effect of NO2 and SO2on ischemic stroke incidence varies at different temperature levels:significant at low temperature but statistically insignificant at high temperature.At low temperature,for every 10μg/m3 increased in the concentration of NO2 and SO2,the percentage increment and 95%confidence interval of ischemic stroke incidence（cumulative lag of 12 days）were 5.95%（3.70%-8.25%）and 16.97%（9.90%-24.49%）,respectively.The result of inter-layer Z-test showed that low temperature could enhance the adverse effect of NO2on ischemic stroke.5.The results of subgroup analysis showed that males and the elderly showed a higher risk in winter and low temperature days（P<0.05）.6.The method of response surface showed that the adverse effect of NO2 and SO2on ischemic stroke was stronger at low temperature.Conclusions:In 2008-2014,the number of new ischemic stroke cases in Shenzhen was on the rise,in which most were male cases,and the proportion of young and middle-aged groups increased.NO2,SO2 and PM10 can increase the risk of ischemic stroke onset,and the effects of NO2 and SO2 on ischemic stroke of certain seasonal and temperature-based law.Cold season and low temperature could significantly strengthen the effect of nitrogen dioxide on the incidence of ischemic stroke. |
