Acoustic Cough—Reflux Associations in Chronic Cough: Potential Triggers and Mechanisms

Background & Aims

Central sensitization is thought to play a role in chronic cough and might explain the temporal association between cough and gastroesophageal reflux (GOR) in patients in whom non-GOR causes have been excluded. Using our novel simultaneous acoustic cough recording and impedance/pH monitoring technique, we aimed to explore this further by assessing such temporal associations and their relationship to the acidity, duration, and proximal extent of reflux and the presence of erosive disease and cough reflex sensitivity in unselected patients (ie, including non-GOR causes) with chronic cough.

Methods

Twenty-four hour ambulatory acoustic cough monitoring with simultaneous impedance/pH recording was carried out in 71 unselected patients with chronic cough, aged 51–64 years (47 female). In addition, all patients underwent cough reflex sensitivity testing to citric acid, and 66 patients underwent gastroscopy. Temporal associations between cough and reflux were expressed using the symptom association probability.

Results

Seventy percent of patients exhibited temporal associations, with 48% having a positive symptom association probability (SAP_R-C) for cough preceded by reflux (mainly distal), 56% a positive symptom association probability (SAP_{C-R (2 min)}) for reflux preceded by cough, and 32% both. Moreover, SAP_R-C positive patients had a more sensitive cough reflex (P = .03) but similar esophageal reflux exposure and erosive disease, together with similar prevalence of extraesophageal causes of cough compared with SAP_R-C negative patients. Reflux immediately following cough was rare.

Conclusions

Cough temporally associates with reflux irrespective of proposed diagnoses, may be self-perpetuating in some patients, and is likely to be driven by central processes.

Keywords: Cough, Gastroesophageal Reflux, Impedance/Ph Monitoring, Symptom Association Probability

Abbreviations used in this paper: 95% CI, 95% confidence interval, BMI, body mass index, C5, 5 coughs, CT, computerized tomography, GOR, gastroesophageal reflux, IQR, interquartile range, LOS, lower esophageal sphincter, SAP, symptom association probability, SAP_C-R, SAP for cough followed by reflux, SAP_R-C, SAP for reflux followed by cough, SAP_{C-R (2 min/10 sec)}, SAP within a 2 minute/10 second time window