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Idrose NS, Walters EH, Zhang J, Vicendese D, Newbigin EJ, Douglass JA, Erbas B, Lowe AJ, Perret JL, Lodge CJ, Dharmage SC. Outdoor pollen-related changes in lung function and markers of airway inflammation: A systematic review and meta-analysis. Clin Exp Allergy 2021; 51:636-653. [PMID: 33539034 DOI: 10.1111/cea.13842] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2020] [Revised: 01/28/2021] [Accepted: 01/29/2021] [Indexed: 12/29/2022]
Abstract
BACKGROUND Experimental challenge studies have shown that pollen can have early and delayed effects on the lungs and airways. Here, we qualitatively and quantitatively synthesize the evidence of outdoor pollen exposure on various lung function and airway inflammation markers in community-based studies. METHODS Four online databases were searched: Medline, Web of Science, CINAHL and Google Scholar. The search strategy included terms relating to both exposure and outcomes. Inclusion criteria were human-based studies published in English that were representative of the community. Additionally, we only considered cross-sectional or short-term longitudinal studies which investigated pollen exposure by levels or season. Study quality assessment was performed using the Newcastle-Ottawa scale. Meta-analysis was conducted using random-effects models. RESULTS We included 27 of 6551 studies identified from the search. Qualitative synthesis indicated associations between pollen exposure and predominantly type-2 inflammation in both the upper and lower airways, but little evidence for lung function changes. People with ever asthma and/or seasonal allergic rhinitis (SAR) were at higher risk of such airway inflammation. Meta-analysis confirmed a positive relationship between pollen season, eosinophilia and eosinophil cationic protein (ECP) in people with ever SAR but the results between studies were highly variable. Heterogeneity was reduced after further subgrouping by age, and the forest plots indicated that eosinophilic airway inflammation to outdoor pollen exposure increased with age. CONCLUSION Among people with ever asthma and ever SAR, exposure to increased ambient pollen triggers type-2 upper and lower airway inflammation rather than a non-specific or innate inflammation. These findings can lead to the formulation of specific pollen immunotherapy for susceptible individuals. Future research should be directed towards investigating lagged associations and effect modifications using larger and more generalized populations. SYSTEMATIC REVIEW REGISTRATION CRD42020146981 (PROSPERO).
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Affiliation(s)
- Nur Sabrina Idrose
- Allergy and Lung Health Unit, Melbourne School of Population and Global Health, The University of Melbourne, Carlton, VIC, Australia.,Centre for Food and Allergy Research (CFAR), Murdoch Children's Research Institute, Parkville, VIC, Australia
| | - E Haydn Walters
- Allergy and Lung Health Unit, Melbourne School of Population and Global Health, The University of Melbourne, Carlton, VIC, Australia.,School of Medicine, University of Tasmania, Hobart, TAS, Australia
| | - Jingwen Zhang
- Allergy and Lung Health Unit, Melbourne School of Population and Global Health, The University of Melbourne, Carlton, VIC, Australia
| | - Don Vicendese
- Allergy and Lung Health Unit, Melbourne School of Population and Global Health, The University of Melbourne, Carlton, VIC, Australia.,Department of Mathematics and Statistics, La Trobe University, Bundoora, VIC, Australia
| | - Ed J Newbigin
- School of Biosciences, The University of Melbourne, Melbourne, VIC, Australia
| | - Jo A Douglass
- Department of Clinical Immunology and Allergy, Royal Melbourne Hospital, Parkville, VIC, Australia.,Department of Medicine, University of Melbourne, Melbourne, VIC, Australia
| | - Bircan Erbas
- School of Psychology and Public Health, La Trobe University, Bundoora, VIC, Australia
| | - Adrian J Lowe
- Allergy and Lung Health Unit, Melbourne School of Population and Global Health, The University of Melbourne, Carlton, VIC, Australia
| | - Jennifer L Perret
- Allergy and Lung Health Unit, Melbourne School of Population and Global Health, The University of Melbourne, Carlton, VIC, Australia
| | - Caroline J Lodge
- Allergy and Lung Health Unit, Melbourne School of Population and Global Health, The University of Melbourne, Carlton, VIC, Australia
| | - Shyamali C Dharmage
- Allergy and Lung Health Unit, Melbourne School of Population and Global Health, The University of Melbourne, Carlton, VIC, Australia
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Abstract
Allergic rhinitis, particularly seasonal allergic rhinitis, is considered a classic Th2-mediated disease, with important contributions to pathology by interleukins 4, 5 and 13. As such, allergic rhinitis is an excellent model for studying allergic inflammation, with findings potentially relevant to the mechanism of lower airways inflammation seen in allergic asthma. However, recent evidence has revealed roles for additional non-Th2 cytokines in asthma, including IL-17 family cytokines and epithelial-derived cytokines. Additionally, putative roles for epithelial-derived cytokines and innate lymphoid cells have been described in chronic rhinosinusitis with nasal polyps. Here, evidence for the involvement of different cytokines and cytokine groups in allergic rhinitis is considered.
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Affiliation(s)
- Guy Scadding
- Allergy and Clinical Immunology, Imperial College, London, South Kensington Campus, London, SW7 2AZ, UK,
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