Asthma and lower airway disease
Indoor fungal diversity and asthma: A meta-analysis and systematic review of risk factors

https://doi.org/10.1016/j.jaci.2014.07.002Get rights and content

Background

Indoor dampness increases the risk of indoor fungal growth. A complex interaction between occupant behaviors and the built environment are thought to affect indoor fungal concentrations and species diversity, which are believed to increase the risk of having asthma, exacerbation of asthma symptoms, or both. To date, no systematic review has investigated this relationship.

Objective

This review aims to assess the relationship between exposure to indoor fungi identified to the genera or species level on asthma outcomes in children and adults.

Methods

Ten databases were systematically searched on April 18, 2013, and limited to articles published since 1990. Reference lists were independently screened by 2 reviewers, and authors were contacted to identify relevant articles. Data were extracted from included studies meeting our eligibility criteria by 2 reviewers and quality assessed by using the Newcastle-Ottawa scale designed for assessment of case-control and cohort studies.

Results

Cladosporium, Alternaria, Aspergillus, and Penicillium species were found to be present in higher concentrations in homes of asthmatic participants. Exposure to Penicillium, Aspergillus, and Cladosporium species were found to be associated with increased risk of reporting asthma symptoms by a limited number of studies. The presence of Cladosporium, Alternaria, Aspergillus, and Penicillium species increased the exacerbation of current asthma symptoms by 36% to 48% compared with those exposed to lower concentrations of these fungi, as shown by using random-effect estimates. Studies were of medium quality and showed medium-high heterogeneity, but evidence concerning the specific role of fungal species was limited.

Conclusion

Longitudinal studies assessing increased exposure to indoor fungi before the development of asthma symptoms suggests that Penicillium, Aspergillus, and Cladosporium species pose a respiratory health risk in susceptible populations. Increased exacerbation of current asthma symptoms in children and adults were associated with increased levels of Penicillium, Aspergillus, Cladosporium, and Alternaria species, although further work should consider the role of fungal diversity and increased exposure to other fungal species.

Section snippets

Search strategy

Electronic searches were conducted on April 18, 2013, and limited to studies published after 1990 in accordance with our protocol (PROSPERO reference: CRD42013004333). In addition to electronic searches, author contacts and references of included studies were conducted in August 2013. The full search strategy was used on all 10 databases (listed in Appendix E1 in this article's Online Repository at www.jacionline.org) to identify eligible articles. The screening process was managed in Endnote

Synthesis

We provide an overarching narrative synthesis of included studies and a meta-analysis of studies of similar design and those reporting ORs and CIs. We included 7 studies in a meta-analysis of Salo et al,30 Araki et al,31 Dales et al,32 Jones et al,33 Li and Hsu,34 Rosenbaum et al,35 and Dharmage et al36 because these met our inclusion criteria for conducting a meta-analysis; the other 10 studies were too heterogeneous to be included. We had planned to prioritize studies rated more highly on the

Discussion

Our findings suggest that exposure to Aspergillus, Penicillium, Cladosporium, Ulocladium, Acremonium, Aureobasidium, Epicoccum, Scopulariopsis, Trichoderma, Alternaria, and Wallemia species might represent a respiratory health risk to asthmatic patients living in homes with increased fungal concentrations. These analyses do not provide sufficient detail to assess whether these fungi exacerbated asthma symptoms or potential health outcomes resulting from increased exposure to known allergenic

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    R.A.S.’s PhD scholarship was funded by the European Social Fund Convergence Programme for Cornwall and the Isles of Scilly and was undertaken in collaboration with Coastline Housing (ESF Phase 1: 09099NCO5 and ESF Phase 2: 11200NCO5). The European Centre for Environment and Human Health (part of the University of Exeter Medical School) is partially financed by the European Regional Development Fund Programme 2007 to 2013 (ERDF Phase 1: 202497 and ERDF Phase 2: 500020) and European Social Fund Convergence Programme for Cornwall and the Isles of Scilly.

    Disclosure of potential conflict of interest: N. J. Osborne has received research support from the European Union, the European Union Social Fund, and the European Union Regional Development Fund; has received consultancy fees from the Centers for Disease Control and Prevention, Office of Science of the National Center for Environmental Health/Agency for Toxic Substances and Disease Registry; and has received payment for manuscript preparation from Living with Environmental Change, United Kingdom. The rest of the authors declare that they have no relevant conflicts of interest.

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