Smoking and reflux - the evidence

In a recent case-control study (Nilsson M et al. Gut 2004; 53(12): 1730-5) it was shown that smoking increases the risk of reflux by 70%. This finding has been reproduced in other studies (Mohammed I et al. Aliment Pharmacol Ther 2005; 21(1): 75-6) that also consistently show associations with many other lifestyle factors.

In another study of 24-hour pH monitoring in reflux patients from San Antonio it was shown that the time the oesophagus is exposed to acid increases by over 50% when smoking 20 cigarrettes a day. These events were mainly daytime ones and patients were twice as likely to experience symptoms after a reflux event. A group from Amsterdam showed that this reflux can affect both the upper and lower oesophagus. Cessation of smoking however takes a while to help: a study on smokers who gave up for a day showed the number of daily reflux episodes reduced but the total oesophageal exposure time did not change. Encouragingly, the use of nicotine patches as an aid to smoking cessation is not associated with any increase in reflux episodes (Louisville, 1999).

Stopping smoking is not universally regarded as being helpful in terms of reflux symptom control. A review of 16 clinical trials looking at impact of lifestyle changes on reflux disease from Stanford suggested that there was no benefit in stopping smoking, though clearly there are well documented other benefits. 

pH monitoring data confirm that smoking increases oesophageal acid exposure. Smoking reduces lower oesophageal sphincter (LOS) pressure and therefore predisposes to reflux. Consistent with this, smoking has been shown to cause an increased number of reflux events that are not attributable to increased transient LOS relaxations, but rather are associated with deep inspiration and coughing. Once reflux occurs, acid is cleared from the oesophagus firstly by oesophageal peristalsis and then by neutralization of the residual acid by swallowed saliva. Smoking prolongs acid clearance by decreasing salivation. The effects of smoking on LOS tone and acid clearance are most likely mainly due to nicotine but are incompletely understood.