| BackgroundAir pollution contributes substantially to premature mortality and disease burden worldwide and ranked the fifth leading global risk factor for disease.China has one of the highest exposure concentrations to air pollution globally.In China,air pollution,particularly fine particulate matter(aerodynamic diameter?2.5 ?m;PM2.5),is a concerning environmental issue that has attracted much attention.PM2.5 is a well-established risk factor for cardiovascular mortality and morbidity.The high blood pressure and high resting heart rate have emerged as powerful independent predictors of cardiovascular mortality and morbidity.It therefore has been hypothesized that the association between PM2.5 and cardiovascular diseases may be explained,in part,by its gradual long-term increasing blood pressure and resting heart rate.Epidemiological evidence on the association between long-term exposure to ambient PM2.5 and hypertension and tachycardia is limited.This thesis aims to investigate the association of long-term(3-year average)ambient PM2.5 exposure with blood pressure and resting heart rate using mega nationwide survey data,the effect modification was also taken into account.Besides,we estimate the disease burden of hypertension and tachycardia attributed to long-term PM2.5 exposures.MethodsThe cross-sectional study of PM2.5 to blood pressure surveyed 39,348,119 reproductive-age(20-49 years)participants from the National Free Preconception Health Examination Project(NFPHEP)during 2010-2015 across China.The analysis of PM2.5 to resting heart rate included 10,427,948 reproductive-age adults from NFPHEP across China in 2015.The estimation of annual average ambient PM2.5 concentrations were realized through employing hybrid satellite-based spatial statistical models.Hypertension diagnosis was defined as systolic BP>140 mm Hg or diastolic BP>90 mm Hg,or self-reported antihypertensive medication use in the past two weeks before the health examinations.Tachycardia was classified as a resting heart rate of>80 beats per minute(bpm).Multi-level logistic regressions adjusted for potential confounding were performed to explore the associations of PM2.5-hypertension and PM2 5-tachycardia.Linear mixed models adjusted for potential confounders were conducted to investigate the associations of PM2.5 with blood pressure and resting heart rate.The natural cubic splines were applied to evaluate the shape of exposure response relationship.The effect modification by sex,age,overweight,smoking status,drinking status,diabetes,urbanity,race,and region was also considered through stratified analyses,and implemented a 2-sample test for assessing statistically significance of the difference between the strata within each subgroup based on the point estimate and standard error.The attributable cases and population fraction were estimated according to the PM2.5-hypertension and PM2.5-tachycardia concentration-response curves.Results1.Effect of ambient PM2.5 on blood pressure and attributable hypertension burden.The mean age for this analysis population was 28 years,and 4.1%of the participants had hypertension.The exposure-response relationship between long-term ambient PM2 5 and hypertension was nonlinear,with threshold concentration of 47.9 ?g/m3.The odds ratio(OR)of hypertension related to a 10 ?g/m3 increase in 3-year average ambient PM2 5 above threshold was 1.010[95%confidence intervals(CI):1.007-1.012].A 10 ?g/m3 increase in PM2.5 above threshold corresponded to a 0.569(95%Cl:0.564-0.573)mm Hg elevation in systolic blood pressure and a 0.384(95%Cl:0.381-0.388)mm Hg elevation in diastolic blood pressure.For hypertension prevalence,the ORs at the 95th percentile of PM2.5 against the thresholds were significantly larger among those who were male,had a BMI<24 kg/m2,smoked,aged 20-34 years old,diabetes,resided in urban areas,other nationality,or lived in in central,south,southwest,northwest,or northeast China.Of the hypertension burden,2.3%(95%CI:2.2%-2.4%)could be attributed to PM2.5 exposures in reproductive-age adult populations.2.Effect of ambient PM2.5 on heart rate and attributable tachycardia burden.The mean age of the participants was 28 years,and 16.3%were classified as having tachycardia.The dose-response relationship between PM2.5 exposure and heart rate were essentially linear.The OR for tachycardia was 1.018(95%CI:1.017-1.020)per 10 ?g/m3 increase in the 3-year average PM2.5 exposure.A 10 ?g/m3 increase in the 3-year average ambient PM2.5 level was associated with a 0.076(95%CI:0.073-0.079)bpm elevation in the resting heart rate.Associations between PM2.5 exposure and tachycardia were significantly stronger in females,older adults,subjects with BMI<24 kg/m2,national minorities,participants residing in urban regions,never-smokers,and never-drinkers.There were 4.0%(95%CI:3.8%-4.3%)of the tachycardia case could be attributed to ambient PM2.5 exposure in Chinese reproductive-age adults.ConclusionsThis is the largest study to evaluate the long-term effects of PM2.5 on blood pressure and heart rate.Long-term PM2.5 exposures were associated with elevated blood pressure and resting heart rate.Exposures to ambient PM2.5 might increase population risk for hypertension and tachycardia.It might be possible to decrease China's avoidable hypertension and tachycardia burden in adults aged 20-49 years through promulgation of formal evidence-based actions to lower ambient PM2.5 levels. |
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