Air Quality, Atmosphere & Health

, Volume 6, Issue 1, pp 47–56

Long-term exposure to air pollution and the incidence of asthma: meta-analysis of cohort studies

  • H. Ross Anderson
  • Graziella Favarato
  • Richard W. Atkinson
Article

DOI: 10.1007/s11869-011-0144-5

Cite this article as:
Anderson, H.R., Favarato, G. & Atkinson, R.W. Air Qual Atmos Health (2013) 6: 47. doi:10.1007/s11869-011-0144-5

Abstract

We quantified the association between long-term exposure to air pollution and the incidence of asthma by conducting a systematic review and meta-analysis of cohort studies. Incidence was defined as the incidence of diagnosed asthma or of new wheeze symptom between two assessments or, in birth cohorts followed up to 10 years of age, a lifetime prevalence estimate of asthma or wheeze symptom. We identified 17 cohorts (eight birth cohorts and nine child/adult cohorts) with a total of 99 population-based risk estimates. The studies were heterogeneous in their design and methods of measurement. Follow-up ranged from 3 to 23 years. Most studies were based on within-community exposure contrasts dominated by traffic pollution. Twelve of the cohorts reported at least one positive statistically significant association between air pollution and a measure of incidence. Of the total of 99 estimates, only a minority (29) were positive and statistically significant. Estimates for meta-analysis were chosen a priori using a protocol. For the 13 studies with estimates for nitrogen dioxide (NO2), the random effects odds ratio was 1.07 (95% CI 1.02 to 1.13) per 10 μg/m3. For five studies with estimates for particulate matter with aerodynamic diameter <2.5 μm (PM2.5), the random effects estimate was 1.16 (95% CI 0.98 to 1.37) per 10 μg/m3. These estimates were reduced in size and statistical significance by adjustment for publication bias but remained positive. The results are consistent with an effect of outdoor air pollution on asthma incidence. Future meta-analyses would benefit from greater standardisation of cohort methods.

Keywords

Air pollutionAsthma incidenceCohortEpidemiologyMeta-analysisReview

Supplementary material

11869_2011_144_MOESM1_ESM.pdf (24 kb)
Online Resource 1Details of literature search (PDF 23 kb)
11869_2011_144_MOESM2_ESM.pdf (49 kb)
Online Resource 2Pollutant conversions and scaling factors (PDF 49 kb)
11869_2011_144_MOESM3_ESM.pdf (15 kb)
Online Resource 3Mapping of reported outcomes to categories for analysis (PDF 14 kb)
11869_2011_144_MOESM4_ESM.pdf (21 kb)
Online Resource 4Algorithms and rules for selecting estimates for meta-analysis (PDF 20 kb)
11869_2011_144_MOESM5_ESM.pdf (32 kb)
Online Resource 5Details of birth cohorts (PDF 31 kb)
11869_2011_144_MOESM6_ESM.pdf (30 kb)
Online Resource 6Details of child/adult cohorts (PDF 29 kb)
11869_2011_144_MOESM7_ESM.pdf (612 kb)
Online Resource 7Details of individual estimates by pollutant and cohort (PDF 612 kb)
11869_2011_144_MOESM8_ESM.pdf (137 kb)
Online Resource 8Cohort studies of air pollution and the incidence of asthma and wheeze symptom. Frequency of estimates and of their direction and statistical significance (PDF 136 kb)
11869_2011_144_MOESM9_ESM.pdf (79 kb)
Online Resource 9Publication bias analyses for the estimates selected for the main meta-analyses of NO2 and PM2.5. (PDF 79 kb)

Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • H. Ross Anderson
    • 1
  • Graziella Favarato
    • 1
  • Richard W. Atkinson
    • 1
  1. 1.MRC-HPA Centre for Environment and Health, Division of Population Health Sciences and EducationSt George’s, University of LondonLondonUK