April 8 (HealthDay News) -- Acid-suppressing medications won't ease asthma symptoms if you don't have heartburn symptoms, too, a new study has found.

Many people with asthma also have gastroesophageal reflux disease, or GERD. But some people have what's known as silent GERD, meaning they have no symptoms.

Doctors have suspected that if people with asthma breathe in during reflux, they might breathe irritating stomach fluids into the lungs. To reduce that possibility, doctors have been prescribing acid-suppressing medications known as proton pump inhibitors (PPI).

But a study in the April 9 issue of the New England Journal of Medicine repots that a PPI probably isn't going to help lessen wheezing in people with silent GERD.

"Patients with asthma that is not adequately controlled with the usual asthma medications, and who have no symptoms of heartburn, but who may or may not have silent GERD, don't seem to have any improvement of asthma when treated with esomeprazole (Nexium)," said one of the study's authors, Dr. Robert Wise, a professor of medicine in the division of pulmonary and critical care medicine at Johns Hopkins University School of Medicine in Baltimore.

Although the two conditions may seem quite different, doctors have long suspected that they're linked, with each disorder possibly triggering the other. Acid reflux might cause asthma symptoms through aspiration of fluid into the airways, or acid might irritate the esophagus and upper airway, according to the study. And asthma might trigger GERD when it causes difficulty breathing. The diaphragm may overinflate, and the extra pressure may cause the esophageal sphincter to herniate, allowing fluids to wash out of the stomach.

Proton pump inhibitors work by suppressing acid production.

The study, which was funded by the American Lung Association and the U.S. National Institutes of Health, included 412 people whose asthma was badly controlled even though they were being treated with inhaled corticosteroids. All had either no symptoms or just minimal symptoms of GERD. They took 40 milligrams of Nexium or a placebo twice a day.

According to Wise, people given the drug took a larger-than-standard dose. In most people, he said, a 40-mg dose would suppress nearly all acid production in the stomach.

There was no statistically significant difference between those who took Nexium and the placebo group with respect to asthma control, lung function, GERD symptoms, night awakenings and quality of life, the study found. The rate of asthma events was 2.3 per person-year for the placebo group and 2.5 events per person-year for the treatment group.

"Our study showed this is not an effective practice," Wise said. "These drugs are effective for treating heartburn, and if you have asthma and heartburn, then these drugs may well be used for those symptoms."

Wise said the researchers were not advocating that anyone stop taking their medications, but that they should talk with their physicians. "People need to follow their doctor's advice and take their asthma medications on a regular basis," he said.

Blair Hains, a spokesman for AstraZeneca, which makes Nexium, said that the drug is not indicated for use in asthma and asymptomatic GERD. "The vast use is around treatment of GERD and heartburn," he said.

"For those who have asthma and have GERD, we want to make sure they continue to take their medications as directed," Hains said. "If you have questions or concerns because you're taking Nexium or another proton pump inhibitor, talk to your doctor."

SOURCES: Robert Wise, M.D., professor of medicine, division of pulmonary and critical care medicine, Johns Hopkins University School of Medicine, Baltimore; Blair Hains, spokesman, AstraZeneca; April 9, 2009, New England Journal of Medicine