Effect of air pollution on prevalence of chronic bronchitis symptoms-a cross-sectional analysis of 5 cohort studies

Abstract

Background and Aims: Chronic bronchitis symptoms are associated with increased risk of COPD and, in some studies, overall as well as COPD mortality. This study aims to assess effects of outdoor air pollution exposures on chronic bronchitis prevalence in five cohort studies participating in the European Study of Cohorts for Air Pollution Effects (ESCAPE) project. Methods: Annual average air pollution exposures of particulate matter (PM) metrics PM2.5, PM10, PMcoarse, PM2.5absorbance, NO2, NOx derived from Land Use Regression models for 2008-2011 and road traffic measures, were assigned to home address of five European cohorts (E3N, ECRHS,NSHD,SALIA,SAPALDIA) at follow-up periods in 2000-2011. Chronic bronchitis was defined as questionnaire-reported chronic cough and phlegm production for ³3 months for 2 or more years. Cross-sectional multivariable logistic regression analyses were conducted in each cohort, adjusting for a confounder set common to all studies (age, sex, smoking status, interview season, education) followed by random-effect meta-analysis. Results: 13,758 and 8,784 participants respectively were included in NO2 and PM analyses at follow-up. Prevalence of chronic bronchitis ranged from 1.5% in E3N (non-asthmatic females) to 6.8% in SALIA (elderly females). No consistent associations were observed between any air pollution measure and prevalence of chronic bronchitis. Meta-analysis combined ORs were: for NO2 OR: 0.96 (95%CI: 0.89-1.04) per 10ug/m3; for PM10 OR 0.85 (95%CI: 0.53-1.39) per 10ug/m3. Results were suggestive of possible effects in asthmatics and never-smokers in some cohorts but this was not consistent across all studies. Conclusions:In contrast to some previously published European studies, this study did not find consistent effects of current air pollution exposures level on chronic bronchitis symptoms. Further investigations including use of back-extrapolated air pollution values to actual year of questionnaire are needed.