| BackgroundHypertension is one of the cardiovascular diseases with highest prevalence in the world,and it is a great public health problem in China and worldwide.It is a serious threat to human health.Epidemiological studies have shown that cardiovascular diseases rank first among the causes of death in China,and has become a major disease of Chinese population.Hypertension is one of the most important risk factors for cardiovascular diseases,50%to 60%of stroke events and 40%to 50%of myocardial infarction events are attributable to elevated blood pressure.The incidence of cardiovascular disease increases as the blood pressure rises above 110/75 mmHg.A number of epidemiological studies have shown the inverse correlation between temperature and blood pressure,where blood pressure increased with the decline of temperature.However,most studies used linear model to analyze the relationship between temperature and blood pressure,and used daily means of temperature exposures,in which blood pressure changes within a few hours cannot be detected.Therefore,this study uses a Distributed Lag Nonlinear Model(DLNM)to analyze the non-linear relationship between temperature and blood pressure.At the same time,the hourly temperature data was used to analyze the transient effect of temperature on blood pressure.We analyze the temperature exposure a few days or a few hours before blood pressure measurement association with blood pressure,to explore the lag effect of temperature on blood pressure.In order to identify sensitive people,we further analyze the effects of short-term temperature exposure on blood pressure in different population subgroups.MethodsStudy participants were from a remote blood pressure meter application promotion project,which was conducted by the Center for Disease Control and Prevention,Gusu District of Suzhou City,Jiangsu Province.We collected information from residents'health record,including basic characteristics,lifestyle,disease history,living environment,etc.Repeated blood pressure measurement data from October 2013 to January 2016,were matched to the meteorological data and air pollution data of Suzhou City during the same period.Meteorological data and air pollution data were divided into two time dimensions,the daily average data and hourly data.We used a Distributed Lag Nonlinear Model(DLNM)and a multi-level regression model to analyze the relationship between daily mean temperature and blood pressure,and the relationship between hourly temperature and blood pressure.By comparing the 1st percentile to the 25th percentile of temperature,the 1st percentile to the 10th percentile,the 99th percentile to the 75th percentile,the 99th percentile to the 90th percentile,we calculated the cold,extreme cold,heat,and extreme heat effects of temperature on blood pressure.We analyzed the lag effect of temperature on blood pressure,with the lag time of the daily average temperature set as 1 day,2 days,3 days to 14 days,and the lag time of the hourly temperature set as 1 hour,2 hours,3 hours to 72 hour.We further conducted stratified analyses to identify sensitive populations according to age,gender,body mass index(BMI),smoking,drinking status,hypertension status,and diabetes status.Results1.The curve of exposure-response relationship between daily temperature and blood pressure for different cumulative lags was nonlinear,and there was a slight difference between different cumulative lag curves.The exposure-response curve between daily average temperature and blood pressure was generally the shape of"parabolic" or "S".In the middle of the curve,the relationship between daily average temperature and blood pressure is almost linear,and the blood pressure decreases with increasing temperature.At both ends of the curve,the change of blood pressure is gradual when the temperature decreases or increases.2.The lag time for the cold and extreme cold effects of daily average temperature on blood pressure was 0-7 days,the cold effects were:with temperature decreased from 7.9 ? to 1.0 ?,systolic blood pressure(SBP)increased by 2.26(95%Cl:0.01,4.51)mmHg,and diastolic blood pressure(DBP)increased by 0.73.(95%Cl:-0.62,2.08)mmHg,pulse pressure(PP)increased by 1.51(95%Cl:-0.02,3.05)mmHg,mean arterial pressure(MAP)increased by 1.24(95%CI:-0.30,2.78)mmHg.The extreme cold effects were:with temperature decreased from 4.5 ? to 1.0 ?,SBP increased by 0.93(95%Cl:-0.40,2.27)mmHg,DBP increased by 0.22(95%Cl:-0.58,1.02)mmHg,and PP increased by 0.71(95%CI:-0.20,1.62)mmHg,MAP increased by 0.46(95%CI:-0.46,1.37)mmHg.The lag time for the heat and extreme heat effects was 0-1 days,the heat effects were:with temperature increased from 23.0 ? to 32.4 ?,SBP decreased by 6.02(95%CI:4.06,7.98)mmHg,DBP decreased by 3.72(95%CI:2.54,4.90)mmHg,PP decreased by 2.30(95%CI:0.96,3.64)mmHg,MAP decreased by 4.49(95%CI:3.14,5.83)mmHg.The extreme heat effects were:with temperature increased from 26.8 ? to 32.4 ?,SBP decreased by 3.40(95%CI:2.05,4.74)mmHg,DBP decreased by 2.17(95%CI:1.36,2.97)mmHg,PP decreased by 1.23(95%CI:0.31,2.15)mmHg,and MAP decreased 2.58(95%CI:1.65,3.50)mmHg.3.Age,BMI,smoking status,hypertension status,and diabete status affect the relationship between daily average temperature and blood pressure.Obese and non-smoking population are more sensitive to the cold and extreme cold effects of daily average temperatures.Elderly,hypertensive,and diabetic patients are more sensitive to the heat effects and extreme heat effects of daily average temperatures.4.The curve of exposure-response relationship between hourly temperature and blood pressure for different cumulative lags was nonlinear,and there was a slight difference between different cumulative lag curves.The exposure-response curve between hourly average temperature and blood pressure was generally the shape of"parabolic" or "S".In the middle of the curve,the relationship between the hourly temperature and the blood pressure is almost linear,and the blood pressure decreases as the temperature rises.At the two ends of the curve,the blood pressure changes more gently when the temperature decreases or rises.Between the cumulative lag of different hours,the cold and heat effects of the hourly temperature on blood pressure are different.5.The lag time for cold effects,extreme cold effects,heat effects,and extreme heat effects of the hourly temperature were 0-5 hours,and the cold effects were:with temperature decreased from 8.1 ? to-0.5 ?,SBP increased 2.31(95%CI:0.98,3.64)mmHg,DBP increased by 1.25(95%CI:0.45,2.05)mmHg,PP increased by 1.05(95%CI:0.15,1.96)mmHg,MAP increased by 1.60(95%CI:0.69,2.51)mmHg.The extreme cold effects were:with temperature decreased from 4.1 ? to-0.5 ?,SBP increased by 0.96(95%CI:0.12,1.81)mmHg,DBP increased by 0.52(95%CI:0.01,1.03)mmHg,and PP increased by 0.44(95%CI:-0.13,1.01)mmHg,MAP increased by 0.67(95%CI:0.09,1.25)mmHg.The heat effects were:with temperature increased from 23.0 °C to 33.2 °C,SBP decreased by 6.16(95%CI:4.23,8.09)mmHg,DBP decreased by 3.88(95%CI:2.72,5.04)mmHg,PP decreased by 2.29(95%CI:0.98,3.61)mmHg,MAP decreased by 4.64(95%CI:3.31,5.96)mmHg.The extreme heat effects were:with temperature increased from 26.8 °C to 33.2 °C,SBP decreased by 3.75(95%CI:2.36,5.14)mmHg,DBP decreased by 2.41(95%CI:1.57,3.24)mmHg,PP decreased by 1.35(95%Cl:0.41,2.30)mmHg,and MAP decreased by 2.85(95%CI:1.90,3.81)mmHg.6.The study did not find that gender,BMI,smoking status affected the relationship between hourly temperature and blood pressure.But DBP and MAP changes in the elderly were more sensitive to extreme heat effects of hourly temperatures,drinking people were more sensitive to the cold and extreme cold effects of hourly temperature,MAP changes in hypertensive patients were more sensitive to extreme cold effects of hourly temperature,PP changes in people with diabetes were more sensitive to heat effects and extreme heat effects of hourly temperatures.Conclusions1.The daily average temperature short-term exposure has cold,extreme cold,heat,and extreme heat effects on SBP,DBP,PP,and MAP.In low-temperature environments,blood pressure rises with decreasing temperature.In high-temperature environments,the blood pressure decreases as the temperature increases.2.The lag time of cold effect and extreme cold effect is 0-7 days,while the lag time for the heat effect and extreme heat effect is 0-1 days.3.Obese and non-smoking population are more sensitive to the cold and extreme cold effects of daily average temperatures.Elderly,hypertensive,and diabetic patients are more sensitive to the heat effects and extreme heat effects of daily average temperatures.4.The short-term exposure of hourly temperature has significant cold,extreme cold,heat,and extreme heat effects on SBP,DBP,PP,and MAP.In low-temperature environments,blood pressure rises with decreasing temperature.In high-temperature environments,blood pressure decreases with increasing temperature.5.The lag time for the cold effect,extreme cold effect,heat effect,and extreme heat effect of the hourly temperature are all 0-5 hours.6.The study did not find that gender,BMI,smoking status affected the relationship between hourly temperature and blood pressure.But drinking people were more sensitive to the cold and extreme cold effects of hourly temperature. |
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