Gastroesophageal reflux ("acid reflux") is common-and often asymptomatic-in people with asthma, and researchers thought there might be a causal connection. Indeed, acid reflux can cause microaspiration that results in bronchoconstriction, and bronchoconstriction can trigger acid reflux. So a research group of the American Lung Association Asthma Clinical Research Centers theorized that if asymptomatic gastroesophageal reflux were an underlying factor in poorly controlled asthma, treating it might improve that control. (Nor were they alone in this thinking; drugs that treat acid reflux are often prescribed in people with asthma.) But their study found otherwise.

Researchers randomly assigned 412 patients with poorly controlled asthma and few or no symptoms of gastroesophageal reflux to receive either esomeprazole 40 mg or placebo twice daily. Participants recorded their morning peak expiratory flow rates, asthma symptoms, and use of [beta]-agonists; they were also assessed with questionnaires and monthly spirometry. The presence of gastroesophageal reflux, determined by ambulatory pH monitoring, was confirmed in about 40% of all participants. Participants were followed for six months; 402 were included in the final analysis.

The primary outcome was "the rate of episodes of poor asthma control." An episode was defined as a 30% or greater drop in the morning peak expiratory flow rate (as compared with baseline) on two consecutive days, an unscheduled health care visit for asthma symptoms, or the need for treatment with oral prednisone. Secondary outcomes were "other asthma symptoms recorded in daily diaries," spirometry results, and questionnaire scores.

Asthma control remained comparably poor in both groups: 42% of patients had an asthma episode that met the definition (this rose to 61% in a secondary analysis in which increased use of [beta]-agonists was added to the definition). Poor asthma control persisted despite the use of a higher-than-usual dosage of esomeprazole (the researchers said they wanted to be sure "there was adequate suppression of gastric acid"). The researchers stated that there was "no benefit" in treating patients with poorly controlled asthma with a proton-pump inhibitor; nor could any subgroups likely benefit from such treatment. They concluded that "asymptomatic gastroesophageal reflux may not be a frequent cause of poor asthma control."

Sylvia Foley

senior editor