Duke Medicine: Coughing 'til morning, parents take warning

They go together like, well, kids and cough. A cold, the flu, even seasonal allergies can set kids off on a coughing binge that lasts forever -- or so it can seem to parents. Eventually, the nagging cough will cease. Until the next cold.

But what about the cough that really, truly doesn’t go away?

“Coughing -- especially coughing at night -- can be a symptom of asthma in children,” says Gregory Metz, MD, of Duke’s Division of Pulmonary, Asthma, and Critical Care Medicine. “In fact, sometimes it is the only one. For this reason, asthma in children often goes undiagnosed.”

Most parents know that wheezing and shortness of breath are telltale signs of asthma. But a cough is easy to chalk up to last month’s cold. “A prolonged cough that persists after the other cold symptoms have disappeared can point to asthma,” says Metz.

Exercise-induced asthma can be just as sneaky, especially in adolescents. “With exercise-induced asthma, there may be no symptoms outside of exercise,” says Metz.

“But during exercise or a few minutes after the child cools down after exertion, there can be coughing and wheezing.” Because the symptoms don’t last, kids often don’t report them, but Metz says that over time, this undiagnosed asthma can limit that child’s activity.

Studies suggest that rates of asthma have increased dramatically in this country in recent years. According to the Centers for Disease Control, about seven million children in the United States under the age of 18 had asthma in 2008. Metz estimates that number to be about 10 million today.

“Nobody completely understands the reason for the increase,” says Metz. “It probably has to do with genetic susceptibility and environmental factors -- that is, changes in how we live.” These changes might include moving from rural to urban settings, changes in air quality, changes in our housing, and exposure to new allergens.

One of the most interesting explanations for the nation’s increase in asthma in this country is the hygiene hypothesis. It goes something like this: When a baby’s immune system is exposed to germs it learns to act as an immune system should -- fighting infection.

In developed countries, environments have become cleaner, and there has been a reduction in childhood illnesses. And in the absence of the pathogens it evolved to fight, the immune system begins responding to things that it’s not supposed to be fighting, such as allergens in the environment or foods.

Although the hygiene hypothesis is unproven, the risk factors for developing childhood asthma are well accepted. They include family history, exposure to cigarette smoke, and presence of allergies, says Metz.

The bad news is that if asthma goes undiagnosed, it can ultimately affect lung function. “Prolonged, untreated asthma can lead to changes in the anatomy of the lungs and predispose you to lung problems,” says Metz. “That can mean exercise limitations, more respiratory illness, and asthma flares.”

There are other conditions that can lead to wheezing, including acid reflux, chronic nasal allergy, vocal cord dysfunction, and, rarely, foreign body aspiration.

To reach a diagnosis of asthma, a physician will take a patient history and conduct a physical exam, as well as perform noninvasive lung function tests in children who are old enough (typically five or six).

If asthma is diagnosed, says Metz, the physician will recommend treatment such as rescue inhalers for exercise-induced asthma, or preventive inhaled steroids to decrease inflammation.

“I think a lot of parents are surprised that their child’s chronic cough is caused by asthma, but they’re also surprised at how dramatically better the child can get with treatment.”