Background: Cough is a very common symptom presenting to medical practitioners. Gastroesophageal reflux disease (GORD) is said to be the causative factor in up to 41% of adults with chronic cough. However cough and GORD are common ailments and their co-existence by chance is high. Also cough can induce reflux episodes. Treatment for GORD includes conservative measures (diet manipulation), pharmaceutical therapy (motility or prokinetic agents, H(2) antagonist and proton pump inhibitors (PPI)) and fundoplication.
Objectives: To evaluate the efficacy of GORD treatment on chronic cough in children and adults with GORD and prolonged cough that is not related to an underlying respiratory disease i.e. non-specific chronic cough.
Search strategy: The Cochrane Register of Controlled Trials (CENTRAL), the Cochrane Airways Group Specialised Register Collaboration and Cochrane Airways Group, MEDLINE and EMBASE databases, review articles and reference lists of relevant articles were searched. The date of last search was 7th April 2006.
Selection criteria: All randomised controlled trials on GORD treatment for cough in children and adults without primary lung disease.
Data collection and analysis: Results of searches were reviewed against pre-determined criteria for inclusion. Two independent reviewers selected, extracted and assessed data for inclusion. Authors were contacted for further information. Data was analysed as "intention to treat" as well as "treatment received". Paediatric and adults data were considered separately. Sensitivity analyses were performed.
Main results: Thirteen studies (3 paediatric, 10 adults) were included. Data from six were available for analysis. None of the paediatric studies could be included in meta-analysis. In adults, analysis on use of H(2) antagonist, motility agents and conservative treatment for GORD were not possible (from lack of data) and there were no controlled studies on fundoplication as an intervention. Six adult studies comparing PPI (2-3 months) to placebo were analysed for various outcomes in the meta-analysis. Enrolment of subjects for two studies were primarily from medical clinics and another 4 studies were otolaryngology clinic patients or patients with laryngitis. Using "intention to treat", pooled data from 4 studies resulted in no significant difference between treatment and placebo in total resolution of cough, Odds Ratio 0.46 (95% CI 0.19 to 1.15). Pooled data revealed no overall significant improvement in cough outcomes (end of trial or change in cough scores). Significant differences were only found in sensitivity analyses. A significant improvement in change of cough scores was found in end of intervention (2-3 months) in those receiving PPI with a standardised mean difference of -0.41 (95%CI -0.75, -0.07) using GIV analysis on cross over trials. Two studies reported improvement in cough after 5 days to 2 weeks of treatment.
Authors' conclusions: There is insufficient evidence to definitely conclude that GORD treatment with PPI is universally beneficial for cough associated with GORD in adults. The beneficial effect was only seen in sub-analysis and its effect was small. The optimal duration of such a trial of therapy to evaluate response could not be ascertained in the meta-analysis although two RCTs reported significant change by 2 weeks of therapy. Clinicians should be cognisant of a period (natural resolution with time) and placebo effect in studies that utilise cough as an outcome measure. Data in children are inconclusive. Future paediatric and adult studies are needed whereby studies should be double blind, randomised controlled, parallel design, using treatments for at least two months, with validated subjective and objective cough outcomes and include ascertainment of time to respond as well as assessment of acid and/or non acid reflux whilst on therapy.