Background: Associations between blood pressure (BP) and ambient air pollution have been inconsistent. No studies have used ambulatory BP monitoring and outdoor home air-pollutant measurements with time-activity-location data. We address these gaps in a study of 64 elderly subjects with coronary artery disease, living in retirement communities in the Los Angeles basin.
Methods: Subjects were followed up for 10 days with hourly waking ambulatory BP monitoring (n = 6539 total measurements), hourly electronic diaries for perceived exertion and location, and real-time activity monitors (actigraphs). We measured hourly outdoor home pollutant gases, particle number, PM2.5, organic carbon, and black carbon. Data were analyzed with mixed models controlling for temperature, posture, actigraph activity, hour, community, and season.
Results: We found positive associations of systolic and diastolic BP with air pollutants. The strongest associations were with organic carbon (especially its estimated fossil-fuel- combustion fraction), multiday average exposures, and time periods when subjects were at home. An interquartile increase in 5-day average organic carbon (5.2 μg/m3) was associated with 8.2 mm Hg higher mean systolic BP (95% confidence interval = 3.0–13.4) and 5.8 mm Hg higher mean diastolic BP (3.0–8.6). Associations of BP with 1–8 hour average air pollution were stronger with reports of moderate to strenuous physical exertion but not with higher actigraph motion. Associations were also stronger among 12 obese subjects.
Conclusions: Exposure to primary organic components of fossil fuel combustion near the home were strongly associated with increased ambulatory BP in a population at potential risk of heart attack. Low fitness or obesity may increase the effects of pollutants.
From the aDepartment of Epidemiology, School of Medicine, University of California, Irvine, CA; bDepartment of Statistics, School of Information and Computer Sciences, University of California, Irvine, CA; cDepartment of Civil and Environmental Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA; dDepartment of Psychology and Social Behavior, School of Social Ecology, University of California, Irvine, CA; and eSusan Samueli Center for Integrative Medicine, and Cardiology Division, Department of Medicine, School of Medicine, University of California, Irvine, CA.
Submitted 23 June 2009; accepted 15 October 2009.
Supported by the National Institute of Environmental Health Sciences grant ES12243, the National Center for Research Resources, NIH, grant MO1 RR00827, the United States Environmental Protection Agency grant RD83241301, the California Air Resources Board contract number 03-329, and by the Larry K. Dodge and Susan Samueli endowed chairs (to J.L.).
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Correspondence: Ralph J. Delfino, Department of Epidemiology, School of Medicine, University of California, 100 Theory, Suite 100, Irvine, CA 92617. E-mail: email@example.com.