Abstract
Background:
The role of socioeconomic position (SEP) as an effect modifier of the association between asthma exacerbations and outdoor air pollution remains unclear.
Objective:
To identify and summarize the evidence regarding SEP as an effect modifier of the association between asthma exacerbations and outdoor air pollution in children.
Methods:
We conducted searches in five electronic databases from January 1950 to June 2015 with no language restriction. Observational studies involving children, measuring any non-biological outdoor air pollutant exposure, resulting in any asthma-related health service use, and reporting measures of effect by individual or aggregated SEP measures were included.
Results:
Ten studies met the inclusion criteria. Five studies reported on hospitalizations, three on emergency department visits, one on ambulatory visits, and one on repeat hospital visits. Six studies identified differential effects of the effect of air pollution on asthma outcomes by SEP with stronger effects for children with a low SEP level; however, the analysis of interaction between air pollutants and SEP was significant in one study of asthma hospitalizations only. The differential effect was reported using individual and aggregated SEP measures.
Conclusion:
This review reveals that there is weak evidence of SEP as an effect-modifier of the association between air pollution and children’s asthma exacerbations. While stronger negative effects on asthma-related hospitalizations occur for children living in a lower SEP, the sample size of some of the original studies limited the statistical assessment of the modification effect.
Acknowledgments
The authors would like to thank Lisa Tjosvold for her valuable support in designing the search strategy for this systematic review.
Author’s contributions: LR-V designed the study, undertook the literature searches, study assessment, data extraction and analysis. CB conducted study assessment and data extraction. CV-R contributed as third reviewer in the selection process and contributed to the data interpretation. MO, AO-V and BR contributed to study design, and data interpretation. All authors contributed in writing and editing the manuscript and approved the final version for publication.
Funding: The study was supported by the Emergency Medicine Research Group (EMeRG) from the Department of Emergency Medicine, and by the Department of Pediatrics, University of Alberta. Dr. Rodriguez-Villamizar is supported by the Colombian Administrative Department for Science and Technology [COLCIENCIAS]. Dr. Villa-Roel is supported by the Canadian Institutes of Health Research (CIHR) in partnership with the Knowledge Translation branch. Dr. Rowe’s research is supported by CIHR through a Tier I Canada Research Chair in Evidence-based Emergency Medicine from the Government of Canada (Ottawa, Ontario).
Appendix
| MEDLINE SEQUENCE AND TERMS | |
| 1. | Air Pollution/ |
| 2. | air pollutants/ or particulate matter/ or sulfur dioxide/ or nitrogen dioxide/ or ozone/ or carbon monoxide/ or polycyclic hydrocarbons, aromatic/ or volatile organic compounds/ |
| 3. | (“air pollution” or “air pollutant”).mp. [mp=title, abstract, original title, name of substance word, subject heading word, keyword heading word, protocol supplementary concept word, rare disease supplementary concept word, unique identifier] |
| 4. | (“ambient air pollution” or “outdoor air pollution”).mp. [mp=title, abstract, original title, name of substance word, subject heading word, keyword heading word, protocol supplementary concept word, rare disease supplementary concept word, unique identifier] |
| 5. | 1 or 2 or 3 or 4 |
| 6. | asthma/ |
| 7. | (“respiratory sounds” or “asthma”).mp. [mp=title, abstract, original title, name of substance word, subject heading word, keyword heading word, protocol supplementary concept word, rare disease supplementary concept word, unique identifier] |
| 8. | (“respiratory symptoms” or “wheez*”).mp. [mp=title, abstract, original title, name of substance word, subject heading word, keyword heading word, protocol supplementary concept word, rare disease supplementary concept word, unique identifier] |
| 9. | 6 or 7 or 8 |
| 10. | Child/ |
| 11. | (“child*” or “adolesc*” or “teen*” or “youth” or “pediat*”).mp. [mp=title, abstract, original title, name of substance word, subject heading word, keyword heading word, protocol supplementary concept word, rare disease supplementary concept word, unique identifier] |
| 12. | 10 or 11 |
| 13. | socioeconomic position/ or socioeconomic factors/ or exp poverty/ or social class/ or exp Social Marginalization/ |
| 14. | (social adj (class* or disadvantage*)).mp. |
| 15. | (deprivation or poverty or “socioeconomic status” or “socioeconomic*”).mp. |
| 16. | 13 or 14 or 15 |
| 17. | 5 and 9 and 12 and 16 |
| 18. | limit 17 to yr=“1950 -Current” |
| EMBASE SEQUENCE AND TERMS | |
| 1. | exp Air Pollution/ |
| 2. | exp air pollutant/ or particulate matter/ or nitrogen dioxide/ or ozone/ or carbon monoxide/ or sulfur dioxide/ or polycyclic aromatic hydrocarbons/ or volatile organic compound/ |
| 3. | (“air pollution” or “air pollutant”).mp. [mp=title, abstract, original title, name of substance word, subject heading word, keyword heading word, protocol supplementary concept word, rare disease supplementary concept word, unique identifier] |
| 4. | (“ambient air pollution” or “outdoor air pollution”).mp. [mp=title, abstract, original title, name of substance word, subject heading word, keyword heading word, protocol supplementary concept word, rare disease supplementary concept word, unique identifier] |
| 5. | 1 or 2 or 3 or 4 |
| 6. | asthma/ |
| 7. | (“respiratory sounds” or “asthma”).mp. [mp=title, abstract, original title, name of substance word, subject heading word, keyword heading word, protocol supplementary concept word, rare disease supplementary concept word, unique identifier] |
| 8. | (“respiratory symptoms” or “wheez*”).mp. [mp=title, abstract, original title, name of substance word, subject heading word, keyword heading word, protocol supplementary concept word, rare disease supplementary concept word, unique identifier] |
| 9. | 6 or 7 or 8 |
| 10. | Child/ |
| 11. | (“child*” or “adolesc*” or “teen*” or “youth” or “pediat*”).mp. [mp=title, abstract, original title, name of substance word, subject heading word, keyword heading word, protocol supplementary concept word, rare disease supplementary concept word, unique identifier]12. 10 or 11 |
| 13. | socioeconomic position/ or socioeconomic factors/ or exp poverty/ or social class/ or exp Social Marginalization/ or exp social status/ |
| 14. | (social adj (class* or disadvantage*)).mp. |
| 15. | (deprivation or poverty or “socioeconomic status” or “socioeconomic*”).mp. |
| 16. | 13 or 14 or 15 |
| 17. | 5 and 9 and 12 and 16 |
| 18. | limit 17 to yr=“1950 -Current” |
| CAB ABSTRACTS, CINAHL, AND SCOPUS | |
| air pollut* OR “ambient air pollution” OR “outdoor air pollution”) ANDTOPIC: (asthma* OR wheez* OR “respiratory symptoms”) ANDTOPIC: (child* OR adolesc* OR teen* OR pediat*) ANDTOPIC: (“socioeconomic position” OR “socioeconomic status” OR “social class” OR “socioeconomic factors” OR “poverty” OR “social class” OR “social status” OR “social marginalization” OR “socioeconomic*”) | |
| Timespan:1950-2015. | |
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