Chronic Traffic-Related Air Pollution and Stress Interact to Predict Biologic and Clinical Outcomes in Asthma Edith Chen,1 Hannah M. C. Schreier,1 Robert C. Strunk,2 and Michael Brauer3 1Department of Psychology, University of British Columbia, Vancouver, British Columbia, Canada; 2Department of Pediatrics, Division of Allergy and Pulmonary Medicine, St. Louis Children's Hospital, Washington University in St. Louis School of Medicine, St. Louis, Missouri, USA; 3School of Environmental Health, University of British Columbia, Vancouver, British Columbia, Canada Abstract Background: Previous research has documented effects of both physical and social environmental exposures on childhood asthma. However, few studies have considered how these two environments might interact to affect asthma. Objective: This study aimed to test interactions between chronic exposure to traffic-related air pollution and chronic family stress in predicting biologic and clinical outcomes in children with asthma. Method: Children with asthma (n = 73, 9–18 years of age) were interviewed about life stress, and asthma-relevant inflammatory markers [cytokine production, immunoglobulin E (IgE) , eosinophil counts] were measured. Parents reported on children's symptoms. Children completed daily diaries of symptoms and peak expiratory flow rate (PEFR) measures at baseline and 6 months later. Exposure to traffic-related air pollution was assessed using a land use regression model for nitrogen dioxide concentrations. Results: NO2 by stress interactions were found for interleukin-5 (β for interaction term = –0.31, p = 0.02) , IgE (interaction β = –0.29, p = 0.02) , and eosinophil counts (interaction β = –0.24, p = 0.04) . These interactions showed that higher chronic stress was associated with heightened inflammatory profiles as pollution levels decreased. Longitudinally, NO2 by stress interactions emerged for daily diary symptoms (interaction β = –0.28, p = 0.02) , parent-reported symptoms (interaction β = –0.25, p = 0.07) , and PEFR (interaction β = 0.30, p = 0.03) . These interactions indicated that higher chronic stress was associated with increases over time in symptoms and decreases over time in PEFR as pollution levels decreased. Conclusions: The physical and social environments interacted in predicting both biologic and clinical outcomes in children with asthma, suggesting that when pollution exposure is more modest, vulnerability to asthma exacerbations may be heightened in children with higher chronic stress. Key words: air pollution, asthma, immune, psychosocial, stress, traffic. Environ Health Perspect 116:970–975 (2008) . doi:10.1289/ehp.11076 available via http://dx.doi.org/ [Online 27 February 2008] Address correspondence to E. Chen, University of British Columbia, Department of Psychology, 2136 West Mall, Vancouver, BC V6T 1Z4 Canada. Telephone: (604) 822-2549. Fax: (604) 822-6923. E-mail: echen@psych.ubc.ca This study was supported by funding from National Institutes of Health grant HL073975 and the Canadian Institutes of Health Research. The authors declare they have no competing financial interests. Received 15 November 2007 ; accepted 26 February 2008. The full version of this article is available for free in HTML or PDF formats. |