Several studies have noted an association between gastroesophageal reflux disease (GERD) and asthma symptoms. Moreover, treatment of reflux may improve or diminish asthma symptoms in patients who have both conditions. Harding and colleagues examined the prevalence and severity of GERD in patients with asthma.

Study subjects had undergone esophageal pH testing over a five-year time period. All subjects with a self-reported diagnosis of asthma were selected from this group. The diagnosis of asthma was confirmed using criteria of the American Thoracic Society (ATS). The criteria included a 20 percent improvement in forced expiratory volume in one second (FEV₁) with use of bronchodilators or a decrease in FEV₁ of 20 percent or greater on methacholine challenge.

GERD was considered present in patients if one or more acid exposure times were abnormal on either the proximal or the distal esophageal pH probe. Specific values were used to quantify the total percentage of the time that the pH measurement was less than 4 during a 24-hour period, compared with healthy volunteers. In addition, ambulatory pH monitoring allowed the patients to record respiratory symptoms (wheezing, cough, shortness of breath) and later correlate these symptoms with esophageal acid events. A positive correlation was made if, when the pH was less than 4, the patient had respiratory symptoms that coincided with the acid episode or occurred less than five minutes later.

From an intial group of 1,983 patients who underwent esophageal pH testing, 358 reported a history of asthma. Of this group, 199 met the inclusion criteria after the ATS guidelines were used to confirm a diagnosis of asthma. The patients were predominantly white women with a mean age of about 45 years. Of the 199 study subjects, 82 percent had a history of reflux symptoms and, after esophageal pH testing was completed, 72 percent had abnormal results. Among the asthmatic patients who did not have reflux symptoms, 29 percent were found to have acid reflux as determined by pH testing. Respiratory symptoms strongly correlated with symptoms of GERD. In symptomatic patients, 64 percent of episodes of wheezing or shortness of breath were associated with esophageal acid, as were 98 percent of episodes of cough.

Among all patients with asthma and GERD defined by pH testing, 78.8 percent of respiratory symptoms were associated with esophageal acid. It was also determined that in patients with symptomatic GERD, reported episodes of heartburn, nausea and regurgitation correlated strongly with the presence of esophageal acid. Interestingly, no difference was noted in lower esophageal sphincter pressure in the 62 symptomatic patients compared with the 56 asymptomatic patients receiving theophylline for asthma.

The authors conclude that there is a strong correlation between GERD and the symptoms of asthma. In patients with asthma and symptomatic GERD, an empiric trial of antireflux medication should be used, and pH testing is probably not necessary. Twenty-four-hour pH monitoring should be considered in patients with asthma that has been difficult to control, since up to one third of these patients may have asymptomatic acid reflux.