Temporal associations between coughing or wheezing and acid reflux in asthmatics

Abstract

Background and aims: The pulmonary symptoms of patients with lung disease may be ascribed to gastro-oesophageal reflux although a causal relationship between acid reflux and coughing or wheezing has not been proved. Does cough cause reflux or does reflux cause cough? The aim of this study was to evaluate 24 hour oesophageal pH tracings of asthmatics with gastro-oesophageal reflux to determine the temporal association between acid reflux and coughing or wheezing.

Methods: The oesophageal tracings of 128 asthmatics from the outpatient clinics who underwent oesophagogastroduodenoscopy, oesophageal manometry, and 24 hour oesophageal pH monitoring were analysed. Three possible temporal relationships between the occurrence of acid reflux and the occurrence of coughs or wheezes were evaluated: (1) pulmonary symptoms preceding reflux; (2) reflux preceding pulmonary symptoms; and (3) unrelated occurrence of both events.

Results: Of 128 asthmatics, 53 recorded five or more coughs and 19 recorded three or more wheezes during the 24 hour recording period. Mean acid contact time was similar in asthmatics with and without pulmonary symptoms (12.2 (1.2)% v 10.4 (0.6)%). Of all coughs and wheezes, 46% and 48%, respectively, were associated with acid reflux. For the individual asthmatic, the likelihood of reflux induced coughing increased as the number of coughs increased.

Conclusions: Half of all coughs and wheezes in asthmatics are associated with acid reflux into the oesophagus. While an occasional coughing episode can lead to reflux, it is rather the reflux episode in the vast majority of instances that leads to cough.

Figure 1

Flow diagram of the study population.

Figure 2

Fraction of coughs preceding reflux (A) and fraction of reflux episodes preceding coughs (B) dependent on the length of the latency period of coughing and reflux episodes, respectively. Each point represents the mean (SD) value calculated from the average values of 53 individual patients.

Figure 3

Influence of the number of coughing episodes on the fraction of coughs preceding reflux (A) and fraction of reflux episodes preceding coughs (B). Only patients with coughing episodes equal to or exceeding the threshold shown on the horizontal axes were included in calculating the mean (SD) value.