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    1 Comment for this article
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    Air pollution and coronary artery calcification: a risk estimation
    Tomoyuki Kawada, MD | Nippon Medical School
    I read with great interest the article by Wang et al [1]. They conducted a cross-sectional study to determine the relationship between indicators of air pollution, traffic exposure and coronary artery calcium (CAC) scores in Chinese adults. The authors concluded that exposures to aerodynamic diameter less than 2.5 μm (PM2.5) and nitrogen dioxide (NO2) were independently associated with severity of CAC. In contrast, ozone (O3) and roadway distance were not significantly associated with CAC by full-adjustment. I have two concerns about their study.

    First, the same authors also reported a prospective study to assess the association among indicators of
    air pollution, change in percent emphysema and lung function [2]. Ambient O3 and oxides of nitrogen (NOx) concentrations, but not PM2.5 concentrations, were significantly associated with greater increases in percent emphysema. In addition, Ambient O3 concentration, but not other pollutants, was significantly associated with a greater decline in forced expiratory volume in 1 second per 10 years. These results indicate that O3 is the most sensitive indicator for pulmonary dysfunction by long-term exposure to ambient air pollutants. Although CAC is a significant predictor for long-term mortality [3,4], risk for different organs might be detected by different indicators of air pollution. I recommend the authors speculating the mechanism of the association.

    Second, the authors adopted two cut-off values, CAC > 0 and >400, as a dependent variable for logistic regression models. Lutsey et al. adopted a cut-off point of CAC >0 for the risk of mortality by obstructive sleep apnea [5]. As the health risk relates to CAC in a dose-response manner [2, 3], I recommend the authors verifying the appropriate cut-off value of CAC, including CAC > 400, for estimating the risk of air pollution.


    References

    1. Wang M, Hou ZH, Xu H, et al. Association of estimated long-term exposure to air pollution and traffic proximity with a marker for coronary atherosclerosis in a nationwide study in China. JAMA Netw Open 2019;2(6):e196553.

    2. Wang M, Aaron CP, Madrigano J, et al. Association Between Long-term Exposure to Ambient Air Pollution and Change in Quantitatively Assessed Emphysema and Lung Function. JAMA 2019:322(6):546-556.

    3. Shaw LJ, Giambrone AE, Blaha MJ, et al. Long-term prognosis after coronary artery calcification testing in asymptomatic patients: A cohort study. Ann Intern Med 2015;163(1):14-21.

    4. Knapper JT, Khosa F, Blaha MJ, et al. Coronary calcium scoring for long-term mortality prediction in patients with and without a family history of coronary disease. Heart 2016;102(3):204-208.

    5. Luyster FS, Kip KE, Aiyer AN, Reis SE, Strollo PJ Jr. Relation of obstructive sleep apnea to coronary artery calcium in non-obese versus obese men and women aged 45-75 years. Am J Cardiol 2014;114(11):1690-1694.
    CONFLICT OF INTEREST: None Reported
    READ MORE
    Original Investigation
    Environmental Health
    June 28, 2019

    Association of Estimated Long-term Exposure to Air Pollution and Traffic Proximity With a Marker for Coronary Atherosclerosis in a Nationwide Study in China

    Author Affiliations
    • 1Department of Epidemiology and Environmental Health, School of Public Health and Health Professions, University at Buffalo, Buffalo, New York
    • 2RENEW Institute, University at Buffalo, Buffalo, New York
    • 3Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, Seattle
    • 4Department of Radiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences, Beijing, China
    • 5Department of Earth System Science, Tsinghua University, Beijing, China
    • 6Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, Georgia
    • 7Department of Medicine, Division of Cardiology, Harbor UCLA Medical Center, Torrance, California
    • 8Department of Biostatistics, University of Washington, Seattle
    JAMA Netw Open. 2019;2(6):e196553. doi:10.1001/jamanetworkopen.2019.6553
    Key Points español 中文 (chinese)

    Question  Are long-term exposure to ambient air pollution and proximity to traffic associated with subclinical atherosclerosis?

    Findings  In this population-based cross-sectional study of 8867 Chinese participants, long-term exposure to ambient nitrogen dioxide and fine particulate matter with aerodynamic diameter less than 2.5 μm was independently associated with a higher coronary artery calcium score, a key atherosclerotic marker. Associations with ozone and proximity to traffic were less consistent.

    Meaning  Long-term exposure to ambient air pollution may be an important risk factor for coronary atherosclerosis.

    Abstract

    Importance  Epidemiologic evidence of the mechanisms of the association between long-term exposure to air pollution and coronary heart disease (CHD) is limited and relies heavily on studies performed in Europe and the United States, where air pollution levels are relatively low. In particular, the association between air pollution and CHD in patients with underlying risks for CHD is understudied.

    Objective  To determine whether air pollution and proximity to traffic are associated with the coronary artery calcium (CAC) score, a key atherosclerotic marker.

    Design, Setting, and Participants  In this prospective, population-based cross-sectional study in a large-scale setting in China, 8867 consecutive patients aged 25 to 92 years with suspected CHD were recruited between November 17, 2015, and September 13, 2017. Participants were excluded if they had previous myocardial infarction, stenting, or coronary artery bypass grafting or incomplete risk factors and exposure data. Each participant underwent assessment of CAC and CHD risk factors at baseline. Data were analyzed from December 2017 to November 2018.

    Exposures  Annual means of fine particulate matter with aerodynamic diameter less than 2.5 μm (PM2.5), nitrogen dioxide (NO2), and ozone (O3) were estimated at the participants’ residences using a validated geostatistical prediction model. Exposure to a nearby roadway was also estimated.

    Main Outcomes and Measures  Computed tomography measurement of CAC score.

    Results  The mean (SD) age of the 8867 participants was 56.9 (10.4) years; 4378 (53.6%) were men. Annual mean (SD) PM2.5, NO2, and O3 measurements were 70.1 (20.0), 41.4 (14.7), and 93.9 (10.5) μg/m3, respectively. The mean (SD) CAC score was 91.4 (322.2) Agatston units. Exposure to PM2.5 and NO2, adjusting for CHD risk factors and multiple pollutants, were independently associated with increases in CAC scores of 27.2% (95% CI, 10.8% to 46.1%) per 30 μg/m3 PM2.5 and 24.5% (95% CI, 3.6% to 49.7%) per 20 μg/m3 NO2. For PM2.5, odds of both detectable CAC (Agatston score >0; odds ratio, 1.28; 95% CI, 1.13 to 1.45) and severe CAC (Agatston score >400; odds ratio, 1.59; 95% CI, 1.20 to 2.12) were increased. Associations of CAC with PM2.5 and NO2 were greater among male participants (PM2.5: 42.2%; 95% CI, 24.3% to 62.7%; NO2: 45.7%; 95% CI, 25.3% to 69.5%) and elderly participants (PM2.5: 50.1%; 95% CI, 28.8% to 75.0%; NO2: 55.5%; 95% CI, 31.8% to 83.6%) and those with diabetes (PM2.5: 62.2%; 95% CI, 30.9% to 101.0%; NO2: 31.2%; 95% CI, 13.9% to 51.0%). Independent association with CAC score was 9.0% (95% CI, −1.4% to 20.4%) for O3 per 15 μg/m3 and 2.4% (95% CI, −0.6% to 5.4%) for distance near roadway per 50% decrease.

    Conclusions and Relevance  In this large Chinese study, long-term exposures to PM2.5 and NO2 were independently associated with severity of CAC. This finding may provide support for the pathophysiological role of coronary atherosclerosis through which air pollution exposure may be associated with CHD.

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