Laryngeal or vocal cord dysfunction has long been regarded as a mimic of asthma; however recent evidence indicates that it may be a significant comorbid condition in asthmatics.
We aimed to systematically estimate the prevalence of comorbid laryngeal dysfunction (LD) in asthmatic adults and to characterize its clinical impact on asthma.
Electronic databases were searched for relevant studies published until June 2019. Studies were included if LD was objectively defined by direct visualization of laryngeal movement. Outcomes included the prevalence of LD and its association with clinical asthma indicators, such as severity, control and quality of life. Random effects meta-analyses were performed to calculate the estimates.
A total of 21 studies involving 1,637 patients were identified. Overall, the pooled prevalence of LD in asthmatic adults was 25% (95% CI: 15-37%; I=96%). Prevalence estimates differed according to the diagnostic test utilized with lowest overall prevalence (4%; 95% CI: 0-10%; I=90%) seen when LD was diagnosed by resting laryngoscopy without external stimuli; however, it was much higher in laryngoscopy studies utilizing external trigger, such as exercise (38%, 95% CI: 24-53; I=90%) or in those using a CT-based diagnostic protocol (36%; 95% CI: 24-49; I=78%). Only seven studies reported the associations between LD and clinical asthma indicators; inconsistencies between studies limited meaningful conclusions.
LD may be a common comorbidity in asthma, affecting about 25% of adult patients. Further prospective studies are needed to better characterize its clinical impact and benefits of detecting and managing LD in asthmatic patients.

Copyright © 2020. Published by Elsevier Inc.