Herbal Medicine for Adult Patients with Cough Variant Asthma: A Systematic Review and Meta-Analysis

Herbal medicine is commonly used by patients with chronic cough, but the role of herbal medicine for cough variant asthma (CVA) has not yet been clearly defined. For the first time, we performed a meta-analysis to integrate the current evidence of randomized controlled trials (RCTs) on this topic and assess the efficacy of herbal medicine in adults with CVA.

A comprehensive search was conducted in electronic databases to identify RCTs of herbal medicine for adult CVA. Cochrane systematic review methods were followed, and the Grading of Recommendations Assessment, Development, and Evaluation was performed to evaluate the quality of evidence.

Twenty-eight RCTs were included. Compared with placebo, moderate-quality evidence from two studies showed that herbal medicine was associated with reduced cough symptom score (CSS) (MD -1.15 points; 95% CI, -1.67 to -0.63) and visual analogue scale (VAS) (MD -1.76 points; 95% CI, -2.66 to -0.86). Compared with montelukast, low- to moderate-quality evidence from 11 studies indicated that herbal medicine was associated with improved Leicester Cough Questionnaire (LCQ) (MD 2.38 points; 95% CI, 1.32 to 3.44), reduced CSS (SMD -0.81 points; 95% CI, -1.09 to -0.53), and VAS (MD -1.34 points; 95% CI, -1.82 to -0.86). There were no significant differences between herbal medicine and ICS plus bronchodilator.

In adults with CVA, herbal medicine may result in improved quality of life and reduced cough frequency and severity scores compared with placebo or montelukast. Herbal medicine was not better than ICS plus a bronchodilator but the evidence is very uncertain.