Effects Of Extreme Temperature On Hospitalization Risk Of Stroke Patients In Nanchang City From 2015 To 2019 Based On Distributed Lag Nonlinear Model

Objective:To analyze the change trend of stroke hospitalization,meteorological characteristics and air pollution levels in Nanchang city from 2015 to 2019,and construct a distributed lag nonlinear model based on temperature,stroke and its different subtypes of Nanchang.According to the age and sex,we identified the sensitive groups,and calculated the burden of disease caused by extreme temperature exposure（population attributable risk percentage and attributable number）.Aiming to provide scientific basis for early identification of stroke patients and sensitive population and carrying out targeted protective measures.Methods:The hospitalization data of stroke patients in 16 secondary and above general hospitals in Nanchang from 2015 to 2019 were collected,and the meteorological factors in Nanchang included daily precipitation,mean temperature,maximum temperature,minimum temperature,atmospheric pressure,humidity,wind speed,wind power,etc.Environmental pollutant data included daily PM_2.5,PM₁₀,SO₂,CO,O₃,etc.Descriptive analysis of air pollutants,meteorological characteristics and stroke hospitalizations was performed by time-series diagrams,the Spearman correlation was used to understand the correlation of hospital admissions with meteorological characteristics and air pollutants in different subtypes of stroke,and a distributed lag nonlinear model was applied to study the exposure-lag-response relationship between extreme temperatures and different stroke subtypes.At the same time,confounding variables such as holiday effect,Long-term trend,day of the week effect were controlled.Identified the sensitive groups by age and sex stratification,and calculated the burden of disease.Results:1)The number of hospitalized stroke patients in 16 hospitals in Nanchang was 79523,including 59,193 patients with ischemic stroke and 20,330patients with hemorrhagic stroke,from 2015 to 2019.The number of males was larger than females.The average age of hospitalized ischemic stroke patients between 18and 65 was 56.26±7.74 years old.The average age of>65 years old was 77.58±7.57years old,the average age of hemorrhagic stroke patients in the 18-65 age group was51.79±10.53 years old,and the average age of>65 years old was 75.03±7.04 years old.The average daily admission number of stroke patients was 43.55±11.13,the minimum was 13,and the maximum was 92.Among them,the average daily admission number of ischemic stroke patients was 32.41±9.53,the minimum was 5,and the maximum was 67.The average daily admission number of hemorrhagic stroke patients was 11.14±4.16,and the minimum was 2.Maximum of 33.The hospitalization rate of stroke in recent five years did not show obvious regularity,but showed an upward trend.The hospitalization rate of ischemic stroke patients in recent five years was consistent with the overall situation of stroke,but the hospitalization rate of hemorrhagic stroke patients showed a cyclical trend of high in winter and spring,low in summer and autumn.2)In the meteorological characteristics of Nanchang from 2015 to 2019,mean temperature and relative humidity showed periodic changes.Mean temperature was the highest from May to August and the lowest from November to March,while air pressure was opposite to mean temperature,which was the highest from November to February and the lowest from May to August.The annual average values of PM_2.5and PM₁₀were（36.49±25.51）μg/m³and（70.71±40.58）μg/m³,respectively,exceeding the ambient air quality standard of the national average annual concentration in class II areas,and showing a trend of periodic change.The pollution was the most serious from November to February of the next year.O₃（57.40±27.47）μg/m³,SO₂（13.68±9.46）μg/m³,NO₂（30.84±14.57）μg/m³did not exceed the annual average limit value.3)The correlation coefficients between mean temperature and PM_2.5,PM₁₀,SO₂,NO₂,CO,O₃,humidity,wind speed,air pressure and rainfall were 0.396,-0.195,0.054,-0.432,-0.235,0.590,-0.175,0.131,-0.891,-0.137,respectively.The correlation coefficients between humidity and PM_2.5,PM₁₀,SO₂,NO₂,CO,O₃,mean temperature,wind speed,air pressure,rainfall were-0.268,-0.490,-0.386,-0.170,0.137,-0.522,-0.175,-0.076,-0.087,-0.007,respectively.The correlation coefficients between wind speed and PM_2.5,PM₁₀,NO₂,CO,O₃,mean temperature,humidity and air pressure were-0.230,-0.222,-0.460,-0.150,0.191,0.131 and-0.076-0.101,respectively.PM_2.5and PM₁₀,NO₂and PM₁₀,PM_2.5,the correlation coefficient between mild air pressure,humidity and rainfall was more than 0.6;4)Mean temperature and stroke and its different subtypes of admission exposure-lag-response curve presented a"V"shape,Extreme low temperature is 4℃and extreme high temperature is 33℃.Extreme high temperature increased the risk of admission to hospital for ischemic stroke,with the relative risk of 1.606（1.342,1.923）,and the cumulative lag effect of high temperature exposure lasted for 14 days.Ischemic stroke was sensitive to extreme hypothermia,with the maximum relative risk of 1.449（1.213,1.731）on the day of hypothermia exposure,and was affected on the first and second days behind,with the relative risk of 1.249（1.166,1.337）and 1.118（1.025,1.220）.The cumulative lag effect lasted up to21 days;5)Ischemic stroke patients≤65 years old were more sensitive to high temperature exposure,with a relative risk of 1.466（1.177,2.765）;male and hemorrhagic stroke patients>65 years old were more sensitive to low temperature exposure,with a relative risk of 1.346（1.082,1.674）,respectively.1.764（1.352,3.771）;6)The total number of people at attributable risk of extreme high temperature and low temperature for stroke were 509 and 1687,and the population attributable risk percentage was 0.641%（-0.321%,1.363%）and 2.10%（1.942%,3.881%）.Among them,426 and 136 patients with ischemic stroke had the attribution risk of extreme high temperature and extreme low temperature respectively,and the population attribution risk was 7.22%（-12.100%,35.662%）and 0.235%（-0.131%,2.873%）.There was no significant difference in the percentage of attributable risk among different genders and age groups.The number of attributable risk among patients with hemorrhagic stroke for extreme high temperature and extreme low temperature was 85 and 1551,and the population attributable risk percentage was0.410%（-0.663%,0.782%）and 7.630%（1.176%.21.544%）,respectively.The number of attributions and population attributional risk percentage of extreme low temperature for men and people aged>65 were higher than those for women and people aged≤65.The number of attributions was 1171 and 1385 respectively,and the population attributional risk percentage was 9.353%（16.025%,29.061%）,10.970%（6.912%,17.111%）,respectively.Conclusions:1)The overall number of inpatients with stroke in Nanchang showed an upward trend in recent five years,and the number of inpatients with hemorrhagic stroke showed a cyclical trend,more in spring and winter,less in summer and autumn;2)In the past five years,air pollution was relatively light.The average annual density of PM_2.5and PM₁₀slightly exceeded the quality standards,but other indicators did not exceed.Only some of PM_2.5and PM₁₀exceeded the second-class average daily density standards,indicating that air pollution was relatively light;3)Patients with ischemic stroke were sensitive to high temperature,increasing their risk of admission,and the risk was highest on the day of exposure,while hemorrhagic stroke was sensitive to low temperature,increasing their risk of admission in the first 3 days of hypothermia exposure;4)Age≤65 years old is the susceptible population to high temperature exposure for ischemic stroke,while male and age>65 were the susceptible population to low temperature exposure for hemorrhagic stroke with high disease burden.