Abstract
Gastro-oesophageal reflux disease is generally considered to be one of the commonest causes of chronic cough, however randomised controlled trials of proton pump inhibitors have often failed to support this notion. This article reviews the most recent studies investigating the mechanisms thought to link reflux and cough, namely laryngo-pharyngeal reflux, micro-aspiration and neuronal cross-organ sensitisation. How recent evidence might shed light on the failure of acid suppressing therapies and suggest new approaches to treating reflux related cough are also discussed.
Highlights
For over 30 years gastro-oesophageal reflux disease (GORD) has been considered to be a cause of chronic cough, either singly or in association with nasal disease and/or asthma [1]
GORD and chronic cough are both common conditions affecting similar populations but without a causal relationship, anecdotal reports of responses to acid suppression are just placebo responses, ii. a variety of criteria have been used for patient selection in studies of acid suppression, which may not have either targeted or allowed the sub-group of chronic cough patients to be identified that were most likely to respond to acid suppression, iii. the acidity of the refluxate may not be of major importance in the pathophysiological processes linking reflux and cough
We have recently shown using synchronized pH/impedance and objective acoustic cough recording that over 70% of patients exhibit temporal relationships between cough and distal oesophageal reflux, with 48% having a positive symptom association probability (SAP) for reflux-cough associations (SAPR-C), 56% having a positive SAP for cough-reflux associations (SAPC-R), and 32% both, raising the possibility of a selfperpetuating cycle maintaining chronic cough [38]
Summary
For over 30 years gastro-oesophageal reflux disease (GORD) has been considered to be a cause of chronic cough, either singly or in association with nasal disease and/or asthma [1]. Temporal associations between reflux and cough Most recent studies using pH/MII monitoring have suggested that patients presenting with chronic cough have physiological numbers of reflux events and oesophageal acid exposure with the vast majority of events being confined to the distal oesophagus (80%) [19,20,21]. Summary of indirect mechanisms In summary, several studies from different laboratories using MII/pH monitoring agree that intra-oesophageal reflux in patients with chronic cough has similar characteristics to that in healthy populations These same studies have found statistically significant temporal associations, suggesting cough follows reflux events more frequently than would be expected by chance alone in up to 50% of patients and independent of pH of the refluxate. It remains to be determined whether pH/impedance parameters or acoustic reflux-cough associations might shed light on which patients may benefit most from surgery
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