NEW YORK (Reuters Health) - Smoking may dull a reflex in the throat thought to protect the airways from stomach-acid reflux, the results of a small study suggest.

Researchers found that smokers showed a slow-down in the pharyngoglottal closure reflex (PGCR), which momentarily closes off the vocal cords when fluid enters the throat. This and other upper-GI reflexes are thought to provide a defense against acids that back up from the stomach.

But in previous research, Dr. Kulwinder Dua and colleagues at the Medical College of Wisconsin in Milwaukee had found that smoking may impair some of these reflexes. According to the researchers, these new findings suggest the habit may weaken the upper airways' acid defenses even further.

Smoking is already thought to weaken the lower esophageal sphincter, the muscle connecting the esophagus and stomach. When this muscle does not work properly, stomach acids may chronically escape back into the esophagus--a condition known as gastroesophageal reflux disease, or GERD.

Because of the proximity of the digestive and respiratory tracts, Dua's team notes, acids that reach the throat may over time harm the airways. If smokers' airway defenses are indeed weakened, this could affect their risk of reflux-related respiratory problems, the researchers explain in their report in the December issue of the journal Gut.

For the study, Dua and colleagues looked at PGCR in response to infusions of water among 10 smokers and 10 nonsmokers. The investigators found that the throat reflex was much slower in smokers than nonsmokers.

Exactly why smoking might affect the pharyngoglottal closure reflex is unclear, the authors note. They speculate that damage to nerve endings in the throat or to tissue lining the throat or esophagus could be to blame.

SOURCE: Gut 2002;51:771-775.

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