Men who smoke may have a less sensitive cough reflex than their nonsmoking counterparts, according to study published in the March issue of Chest, the journal of the American College of Chest Physicians.

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Researchers from Albert Einstein College of Medicine in Bronx, N.Y., found that young, healthy males who smoke have a cough reflex that is slower to react than nonsmoking males.

A person's reflex to cough is a defensive action that prevents foreign material from entering the respiratory tract and helps to remove mucus from the airways.

"Little research has been conducted in the field of cough, and even less research has been done on cough reflex sensitivity in relation to tobacco smoke," said study leader Dr. Peter Dicpinigaitis. "Diminished cough reflex inhibits an important defense mechanism which may make smokers more prone to respiratory tract infections and other medical conditions."

Researchers measured cough reflex sensitivity in 20 healthy men with an average age of 32.2 who currently smoked at least five cigarettes daily for the past year. Men were studied because past research indicates that cough reflex is significantly more sensitive in women.

Volunteers underwent cough challenge testing, which included inhaling single breaths of the agent capsaicin, a standard cough inducer, at one-minute intervals until five or more coughs were induced.

Researchers found that smokers needed more than four times the concentration of capsaicin than nonsmokers to induce five or more coughs.

"Long-term exposure to tobacco smoke may desensitize cough receptors in the airway, increasing the tolerance to tobacco smoke and other inhaled substances," Dicpinigaitis said. "We can speculate that as individuals become less exposed to tobacco smoke, their cough receptors become less inhibited, resulting in a more sensitive cough reflex. This may be the reason why former smokers briefly develop a cough after smoking cessation."

"Although difficult to prove, it also is likely that healthy smokers have a naturally blunted cough reflex," wrote Dr. Umesh G. Lalloo, of Nelson R. Mandela School of Medicine in South Africa, in a corresponding editorial. "This may explain why some individuals tolerate the acute effects of smoking and become addicted to nicotine."