| BackgroundCardiovascular disease(CVD)as the leading cause of death in China,has become an important public health problem affecting the population health and life expectancy in the global.Although several studies have estimated the attributable burden of CVD associated with hypertension and obesity,the limited sample-size and sub-regions,difference in characteristics among participants and the definition for risk factors making the previous results lack of comparability and representativeness.More importantly,several studies at abroad have indicated that the attributable burden associated with hypertension and obesity varied across race and geographical regions,however,far less is known about regional-level attributable burden associated with hypertension and obesity associated with CVD in China.In the context of global climate change,epidemiology evidence is absent in the impact of long-term temperature variability(TV)and attributable risk,and the impact in attributable risk of hypertension and obesity associated with CVD,when exposure to different TV level.ObjectiveThe current study was aimed to estimate the provincial-level attributable risk of CVDs associated with hypertension,high body mass index(BMI)and abdominal obesity;and to explore the effect of long-term TV on the incidence of CVD and attributable risk in China;and the impact in attributable risk of hypertension and obesity associated with CVD,when exposure to different TV level.Methods1.The China Hypertension Survey(CHS)involved a nationally representative sample nearly 0.5 million aged ?15 years in all 31 provinces of China's mainland from October 2012 to December 2016 using a stratified multistage random sampling methods,of which,325,552 participants aged ?35 years were used to estimate the exposure level of hypertension,BMI,waist circumference and TV.2.Out of the newest CHS participants,30,036 individuals aged ?35 years were followed up from 2017 to 2019.The overall rate of follow-up was 87.65%.After exclusions of 3,709 participants who drop out in the 5-years follow up,2,330 participants with prior CVD history,276 with missing data on important risk factors,such as smoking and education,finally,23,721 participants entered the final analysis,which were used to calculate the multivariable-adjusted hazard ratio(HR)and 95%confidence intervals(CI)by Cox regression for hypertension,high BMI,abdominal obesity and TV.Hypertension were defined as systolic blood pressure ?140 mmHg,diastolic blood pressure ?90 mmHg or diagnosed by hospital at least county or district level or received anti-hypertensive treatment in the last two weeks;overweight,obesity were defined as BMI between 24.0 Kg/m2 and 28.0 Kg/m2 and BMI ?28.0 Kg/m2,respectively;high BMI was defined as BMI ?24.0 Kg/m2;abdominal obesity was defined as waist circumference ?90 cm for men or waist circumference ?85 cm for women;TV was defined as the standard deviation of daily temperatures during survey years and was categorized into tertiles(T1?8.78?,T2 between 8.78 and 10.07?,T3?10.07?).3.HRs along with the representative exposure level,were used to calculate the population attributable fraction(PAF)according to counterfactual scenarios for theoretical minimum risk exposure levels,and the 95%CI for PAFs associated with hypertension,high BMI,abdominal obesity and TV were estimated using a bootstrap simulation method.4.CVD-free years loss was calculated using the trapezium rule to estimate the reduced disease-free years for hypertension,high BMI,abdominal obesity and TV.5.Stratified analysis were used to estimate the impact of attributable risk of hypertension,high BMI,abdominal associated with CVD when exposure to different TV level.Results1.Baseline characteristics of participantsThe CHS enrolled 325,552 participants aged ?35 years,52.85%were female,with mean age of 56.75±13.88years.For the follow-up participants,of 23,721 aged?35 years participants were included,53.69%was female and the mean age was 56.15±13.08 years.During mean follow-up of 4.62 years,the current study ascertained 836 cases of incident CVD.2.The association between hypertension,obesity,TV and CVDAfter adjusting for many confounders,significant association between hypertension,obesity,TV and CVD were observed,the HRs(95%CI)were 1.78(95%CI:1.53-2.08)for hypertension and 1.21(95%CI:1.05-1.40)for high BMI,respectively;For TV,comparing with lowest TV exposure group,participants exposure to the medium and highest tertile with an HR(95%CI)=1.34(95%CI:1.13-1.59)and 1.72(95%CI:1.35-2.19)for CVD.TV on a continuous scale,for per 1? increase in TV,there was a 6%increase of CVD.3.Attribution risk associated with hypertension,obesity and TVIn the Chinese population aged ?35 years,the PAF of CVD associated with hypertension,high BMI,abdominal obesity,T2 and T3 TV were 20.43%(95%CI I:20.26%-20.63%),9.65%(95%CI I:9.69%-9.74%),10.61%(95%CI I:10.50%-10.70%),7.41%(95%CI:7.35%-7.49%)and 16.95%(95%CI:16.84%-17.06%),respectively.Hypertension,abdominal obesity and TV had the highest PAF for CVD.The PAF for grade 1,2 and 3 hypertension were 13.01%(95%CI:12.92%-13.11%),5.78%(95%CI:5.68%-5.88%)and 3.88%(95%CI:3.79%-4.00%),respectively,4.19%(95%CI:0.00%-4.25%)and 6.25%(95%CI:6.33%-6.41%)for overweight and obesity,respectively.Higher PAF for grade 1 hypertension was observed.Substantial disparities in PAF related with above risk factors were observed.At the provincial level,the highest PAF of CVD related hypertension was 27.39%in Beijing,and the lowest was 14.02%in Hunan.The highest PAF of CVD related with high BMI was 12.79%in Beijing and the lowest was 5.70%in Guangxi.The highest PAF of CVD related with abdominal obesity was 18.40%in Beijing,and the lowest was 3.38%in Guangxi.4.Disease-free years estimationParticipants with hypertension,high BMI,abdominal obesity and higher TV would lose 2.51,0.43,0.55 and 2.11 CVD-free years for the population aged 35 to 65 years.5.The impact in PAF of hypertension and obesity in different TV levelAt the national level,except for hypertension,the PAF of CVD associated with high BMI and abdominal obesity is higher when exposure to the higher TV.The PAF of CVD related with hypertension was 22.65%(95%CI:22.48%-22.82%)and 15.42%(95%CI:15.27%-15.56%),3.55%(95%CI:3.52%-3.57%)and 13.84%(95%CI:13.76%-13.91%)with high BMI,9.86%(95%CI:9.76%-9.95%)and 10.45%(95%CI:10.37-10.55%)with abdominal obesity,when exposed to the lower and higher TV,respectively.ConclusionThe current study showed significant association between hypertension,obesity,TV and CVD,and substantial proportion of CVD could be attributable to hypertension,abdominal obesity and TV,with great provincial-disparities in PAF of CVD associated with hypertension and obesity,there was notable difference in PAF associated with hypertension and obesity when exposure wo different TV level.The current findings will help to guide local policy makers in high-middle income countries,to develop provincial-level effective primary prevention of CVD,according to local climate,also help for reducing greebhouse effect,and developing extreme weather warning system and individual-level protection to reduce related health harm. |
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