It is estimated that more than 75% of patients with hard-to-treat asthma also experience frequent heartburn from a condition called gastroesophageal reflux disease (GERD). People with asthma are twice as likely to have GERD as people who do not have asthma, especially those with treatment-resistant asthma.
GERD is the backward flow of acidic stomach content into the esophagus (acid reflux). Usually, stomach acid is kept in the stomach by a muscular ring at the bottom of the esophagus called the lower esophageal sphincter. If this sphincter becomes relaxed, it can allow stomach contents to back up into the esophagus, producing a burning sensation that is commonly referred to as heartburn. GERD can irritate asthma and damage the esophagus. It is believed that asthma attacks can also cause the sphincter to relax, making it easier for acid reflux to occur.
As previously mentioned, the exact link between the two conditions is uncertain. However, there are a few possibilities as to why GERD and asthma may coincide. One possibility is that the acid reflux irritates the airways and lungs, which affects breathing and may make people more sensitive to outside conditions such as air pollution, cigarette smoke, and cold air.
Another potential link to asthma for patients with GERD is that when acid enters the esophagus, a nerve reflex is triggered, causing the airways to narrow in order to prevent the acid from entering.
Some asthma medications can increase heartburn and other symptoms of GERD. Theophylline has been most closely tied to worsening GERD symptoms. Bronchodilators (a common type of inhaled asthma medication) may reduce the lower esophageal sphincter pressure and trigger GERD symptoms. However, further studies must be done before the relationship between GERD and these drugs is fully understood.