Traditional medicines for asthma in children and adults: A systematic review of placebo-controlled studies

Background: Traditional medicines (TMs) adjunctive to conventional medications are widely used for asthma in east-Asia and have gained popularity in western countries. Objective: To assess the efficacy and safety of TMs for asthma in children and adults based on placebo-controlled trials in order to inform physicians and assist them in discussions with patients. Methods: Seventeen electronic databases were searched. Participants had acute or chronic asthma. Interventions included orally administered traditional medicines used in east-Asia. Outcomes included lung function, symptoms, quality of life, exacerbations, medication use and safety. RevMan 5.3 (random effect model) was used for meta-analysis. Baseline values were assessed for balance and asthma severity. Within-group changes were calculated to assess minimal clinically important difference (MCID). Results: Eighteen studies (2080 participants) were included. All combined TMs with conventional medicines. The single study of acute asthma (n = 300) showed an improvement. For chronic asthma, severity at baseline ranged from very mild to severe. When asthma was mild, significant differences in lung function (FEV1%, PEF/R) were not detectable. When participants had moderate and/or severe asthma at baseline improvements were more evident. For measures of lung function, improvements within the TM groups tended to be greater when the asthma was more severe. Some studies showed MCIDs. No serious adverse events or interactions were reported but safety data were incomplete. Conclusions: The application of certain traditional herbal medicines used in east-Asia as adjuncts to conventional medications improved outcomes in acute and chronic asthma, but most evidence was based on single trials. Therefore, no single TM could be recommended. Effect sizes varied according to asthma severity at baseline. Future studies should consider baseline severity when enrolling participants.