By DR. KITTU JINDAL GARG, ABC News Medical Unit
Parents who smoke could be killing their child's cough reflex - a natural defense against potentially unhealthy particles that enter the airway - new research suggested.
While the natural inclination may be to assume that kids in smoky households cough more, the new study, published Monday in Oxford Journal's Nicotine & Tobacco Research, showed exactly the opposite.
A cough serves to help an individual clear his or her airway and protect the lungs from irritating chemicals, food, bacteria or smoke. These irritants normally trigger a cough reflex when they enter the airway.
Smoking adults are known to have an impaired cough reflex and, hence, a higher "cough threshold." In other words, these individuals cannot cough until higher levels of irritating substances are in their airways. The question the researchers sought to address was whether the same principle applies to children.
Paul Wise, psychologist at the Monell Chemical Senses Center in Philadelphia, and his colleagues studied 38 healthy children between the ages of 10 and 17, roughly half of whom came from households with smoking parents and half who had never been exposed to smoke in their household.
These children were asked to inhale a chemical irritant known as capsaicin - the burning ingredient found in chili peppers. Researchers made the children breathe in higher and higher levels of this pepper spray until they coughed twice; this was determined to be their "cough threshold."
Because capsaicin normally causes irritation of the airway in even very small doses, inhaling a small quantity of the substance directly triggers the cough reflex in normal individuals.
The researchers found that the children who came from homes in which parents smoked at least 10 cigarettes a day required twice the amount of capsaicin as the other children before they reached their cough threshold.
Doctors not involved with the study said the findings are important.
"This study is the first to show that secondhand smoke exposure actually blunts a child's cough response," said Dr. Fernando Urrego, head of pediatric pulmonology at Ochsner Children's Health Center in New Orleans.
"The child's innate defense mechanism to clear the airway of irritants does not function," Urrego said. "These findings may explain why children exposed to secondhand smoke exposure are more likely to have colds … and may also explain why some exposed children have more pneumonias, as they cannot clear secretions from their lower airways."
The study added yet another potential health consequence of secondhand smoke for children.
"The surgeon general has stated there is no safe amount of secondhand exposure," said Dr. Sonika Bhatnagar, assistant professor of pediatrics at Children's Hospital of Pittsburgh of UPMC. "[I am] concerned about the millions of children … who are exposed to secondhand smoke 24/7 in their homes."
This study may also point to one reason why children of smokers are more likely to be smokers in the future, because they will not experience as much unpleasant irritation to their throat from cigarette smoke.
"This is certainly a topic which would be helpful to study further," said Dr. Michael Cohen, pediatric ear, nose and throat specialist at Massachusetts Eye and Ear Infirmary and Harvard Medical School.
He added that the study stood as further evidence that parents who quit smoking are doing both themselves and their children a favor.
"Quitting smoking," Cohen advised, "can meaningfully improve the health of you and your child."