When Debra Peterson tells her patients their worsening asthma symptoms may be related to gastroesophageal reflux disease, or GERD, they look at her with shock.

“People are surprised because we are not gastrointestinal doctors,” said Peterson, a family nurse practitioner with Advancements in Allergy and Asthma Care in Minnetonka, Minn. “However, we see a lot of association between asthma and acid reflux. In the 15 million [Americans] who have asthma, as many as 50 to 80 percent also have acid reflux.”

But many patients fail to recognize this association because the classic symptoms of acid reflux –- heartburn and/or regurgitation –- may be absent.

“There’s no clear-cut cause and effect,” Peterson said. “We do know that reflux can cause asthma if the reflux is aspirated into the lungs. Or, the acid in the esophagus can cause chest tightness. Also, if acid gets into the bottom of the esophagus, it can reflux up against the bronchial nerve, which causes the airways to narrow and a shortness of breath.”

Also, some asthma medications, including bronchodilators, such as theophylline, have been known to trigger acid reflux, Peterson said.

Peterson said she becomes suspicious of an acid reflux/asthma connection if the patient:

— Complains of a nighttime cough;

— Notices his asthma becomes worse after eating a big meal, drinking alcohol or lying down;

— Was diagnosed with asthma as an adult;

— Has poor asthma control, even when taking prescribed asthma medication.

Peterson’s patients often notice an improvement in their asthma once they start taking proton pump inhibitors such as Nexium, Protonix or Prilosec, which are commonly prescribed for acid reflux and GERD.

“My patients will say, ‘Oh, that tightness in the middle of my chest isn’t there anymore,’” Peterson said. “When a patient thinks of reflux, they think of heartburn, or regurgitation, and they aren’t aware of the other atypical signs.”

If a patient’s asthma symptoms do not get better with PPIs, they are typically referred to a gastroenterologist.

“It’s not uncommon anymore to get referrals from allergists and pulmonologists,” said Dr. John Allen, chair of the American Gastroenterology Association clinical practice committee and medical director of Minnesota Gastroenterology in St. Paul, Minn. “I’ve seen it increasing over the last five years.”

For these patients, gastroenterologists often want to perform an endoscopy, which involves inserting a thin camera down the patient’s throat and into the esophagus. Once inside the esophagus, doctors can place a capsule that will record the patient’s pH levels over the course of the next 48 hours.

"Sometimes surgery is needed to tighten up the esophageal sphincter, which prevents the reflux of acid," Allen said.

Scientists are still somewhat baffled by the association between the two conditions, but much research is being done.

Recently, researchers at Duke University Medical Center in North Carolina conducted a study in an effort to find the link between the conditions.

Dr. Shu Lin, an assistant professor of surgery and immunology at Duke, found that the immune systems of mice produced changes that drive the development of asthma in mice once they inhaled small amounts of stomach fluid that backed up into the esophagus.

“This is the first experimental evidence in a controlled, laboratory setting linking these two very common conditions in humans,” Lin said in a study published online in the European Journal of Clinical Investigation. “These data suggest that chronic micro-aspiration of gastric fluid can drive the immune system toward an asthmatic response.”

“This does not mean that everyone with GERD is going to develop asthma, by any means,” said William Parker, assistant professor of surgery at Duke and co-author of the study. “But it may mean that people with GERD may be more likely to develop asthma. If there is an upside to this, it is that developing GERD is something we can pretty much treat and control.”

Click here to read more about Lin and Parker's study (subscription required).