History of allergic rhinitis and risk of asthma; a systematic review and meta-analysis

Abstract

Background:Allergic rhinitis has been suspected to be a risk factor for asthma in several studiesbut this association is notfirmly established. The objective of this study was to synthesize theevidence of the association between allergic rhinitis and the risk of asthma through a systematicreview and meta-analysis.Methods:We performed a search in Medline, Scopus, ISI Proceedings databases and otherdatabases from inception until February 2019, followed by manual search to identify potentiallyrelevant case-control and cohort studies that reported relative risk estimates and confidence in-tervals of the association between allergic rhinitis and asthma. Cross-sectional studies wereexcluded. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated usingfixedand random effects models and quality of studies was assessed through a modified version of theNewcastle-Ottawa scale. Results:Twenty-nine eligible studies, 22 cohort and 7 case-control studies, with a total of 274489subjects, were included in the meta-analysis. The results show that history of allergic rhinitis issignificantly associated with the occurrence of asthma (OR¼3.82; 95% CI: 2.92–4.99). Europeanstudies showed a stronger association (OR¼4.35; (95% CI: 3.12–6.06) than non-European studies(OR¼2.75; 95% CI: 2.16–3.50), and case-control studies showed a stronger association(OR¼4.71; 95% CI: 3.58–6.17) than cohort studies (OR¼3.42; 95% CI: 2.60–4.50). Conclusions:This meta-analysis shows that allergic rhinitis is strongly associated with asthma.Further prospective studies on the effect of treatment of allergic rhinitis on the development ofasthma are needed. Relief of airway allergic manifestations may need dual control of allergicrhinitis and asthma.