The association between gastro-oesophageal reflux disease and asthma: a systematic review

Background and aim: Gastro-oesophageal reflux disease (GORD) has been linked to a number of extra-esophageal symptoms and disorders, primarily in the respiratory tract. This systematic review aimed to provide an estimate of the strength and direction of the association between GORD and asthma. Methods: Studies that assessed the prevalence or incidence of GORD in individuals with asthma, or of asthma in individuals with GORD, were identified in Medline and EMBASE via a systematic search strategy. Results: Twenty-eight studies met the selection criteria. The sample size weighted average prevalence of GORD symptoms in asthma patients was 59.2%, whereas in controls it was 38.1%. In patients with asthma, the average prevalence of abnormal oesophageal pH, oesophagitis and hiatal hernia was 50.9%, 37.3% and 51.2%, respectively. The average prevalence of asthma in individuals with GORD was 4.6%, whereas in controls it was 3.9%. Pooling the odds ratios gave an overall ratio of 5.5 ( 95% CI 1.9-15.8) for studies reporting the prevalence of GORD symptoms in individuals with asthma, and 2.3 ( 95% CI 1.8-2.8) for those studies measuring the prevalence of asthma in GORD. One longitudinal study showed a significant association between a diagnosis of asthma and a subsequent diagnosis of GORD ( relative risk 1.5; 95% CI 1.2-1.8), whereas the two studies that assessed whether GORD precedes asthma gave inconsistent results. The severity-response relationship was examined in only nine studies, with inconsistent findings. Conclusions: This systematic review indicates that there is a significant association between GORD and asthma, but a paucity of data on the direction of causality.