| BackgroundAir pollution exposure is a signi icant public health problem with substantial implications for human disease globally, especially in China. The updated global burden of disease report has once again highlighted the importance of air pollution as an important risk factor contributing to global mortality. Ambient air pollution ranked fourth and household air pollution ranked ifth in terms of the age-standardised disability-adjusted life-years rate in2010in China. Epidemiological indings have demonstrated a consistent increased risk for cardiovascular diseases in relation to exposure to air pollution that increases susceptibility to cardiovascular events and contributes to morbidity and mortality worldwide. These associations have been reported typically at relatively low ambient levels of particulate matter with aerodynamic diameter less than2.5μm (PM2.5) air pollution in North America and Europe. And black carbon (BC) has gained attention as a product and marker of combustion-related anthropogenic air pollution, often showing independent health associations distinct from those induced by background ambient PM2.5. Whether these adverse effects persist in relation to the folds higher air pollution and high level BC concentrations encountered in East Asia is unknown.ObjectiveIn this prospective study, we investigated the association between personal level exposure to BC as well as ambient PM2.5with24-hour ambulatory blood pressure (ABP) and24-hour heart rate variability (HRV) as well as endothelial function, arterial stiffness and laboratory measures in a cohort of individuals with the metabolic syndrome living in Beijing, China, and who are chronically exposed to high pollution levels.MethodsSubjects with metabolic syndrome (n=65) were recruited. Inclusion criteria were nonsmoking adults living in a smoke-free home in Beijing. Metabolic syndrome was de ined by International Diabetes Federation criteria speci ic for Asians. Baseline measurements, including body mass index, waist circumference, and waist-to-hip ratio and self-reported questionnaire were collected in the screen visit. Eligible patient then went through4rounds of visits every3months, each consists of5days.Brie ly, during day0, subjects arrived at the clinic and were it with the black carbon monitor and a global positioning device. Personal BC was measured every5minutes during the5-day period. Ambient PM2.5concentrations, temperature and relative humidity were obtained. The participants were encouraged to partake in their usual daily activities and maintain a diary during the5-day period, during which they wore personal exposure monitors.On day4, they wore the ABP monitoring and Holter monitor for24hours and completed a diary de ining their activities and locations for each half-hour period. Systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate were measured repeatedly every20minutes during daytime and every30minutes at night-time during a24-hour period. Frequency and time domain HRV parameters were analyzed in the same frequency to match with ABP measurements.On day5, endothelial function was measured by the reactive hyperemia index (RHI). Pulse wave velocity (PWV) and central aortic BP were estimated with a noninvasive device. Fasting blood samples were drawn from subjects on day5and routine laboratory evaluations were conducted (lipid pro ile, creatinine, glycohemoglobin et al.). All patients were enrolled between February14,2012, and July14,2012. And the forth visit inished in July4,2013.Serum high-molecular-weight adiponectin (HMW-APN), leptin and angiotensin Ⅱ (ANG-Ⅱ) were tested using enzyme-linked immunosorbent assay (ELISA).Standard multiple linear regression models and generalized additive mixed models are used in single/summary outcome measures and data with repeated measures, respectively.ResultsDuring the whole study period, the average of ambient PM2.5(101.1μg/m3; SD,94.9μg/m3) was folds higher than the US National Air Quality Standard (<15μg/m3). The mean of the5-day personal BC (5.3μg/m3; SD,5.2μg/m3) was substantially higher than the average urban BC concentrations in North America. BC concentrations were correlated with that of PM2.5.In the irst visit, positive association was observed between personal BC and BP for averaging periods ranging from6to10hours. Effects of BC on changes for ambulatory SBP were slightly greater in magnitude than for DBP, with an increase of2.2mm Hg (95%CI,0.61-3.5mmHg) in SBP and an increase of1.6mm Hg (95%CI,0.3-2.3mmHg) in DBP for1μg/m3increase in BC during the previous10hours. The7-hour moving average of personal BC was found to be marginally associated with frequency domain low frequency to high frequency ratio (LF/HF) and mean R-R interval (meanRR). Longer averaging times showed stronger magnitudes of association in LF/HF and mean R-R interval, with the largest associations exhibited for the10-hour moving average that a1μg/m3increment in personal BC was associated with5.11%(95%CI,0.62-9.60%) increase of LF/HF and0.06%(95%CI,0.01-0.11%) reduction of mean R-R interval, respectively. There was no signi icant association between different lags or moving averages of BC or PM2.5with either endothelial function or arterial stiffness measures.The integrated data of four visits showed positive association between personal BC and Aortic SBP and DBP. Decreased RHI in females and reduced PWV in males were observed.There exhibited no signi icant association between personal BC and HMW-APN and leptin, but ANG-II was negatively associated with acute exposure of BC.ConclusionsThe results demonstrate an effect of anthropogenic combustion-related air pollution (BC) on BP and HRV in patients with metabolic syndrome in Beijing, a city continually facing extreme levels of air pollutants. The relationship between urbanization and hypertension may have complex underpinnings, with factors such as air pollution contributing to increases in blood pressure via autonomic alterations. Other mechanism remains need further study. |
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