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As many as 1 in 10 children in the U.S. have asthma, a lung condition that is responsible for one-quarter of all emergency room visits each year. About 1 in 20 adults have chronic obstructive pulmonary disease (COPD), which is the fourth leading cause of death in the U.S.
Experts think the two lung conditions are unrelated, although both can cause coughing, shortness of breath, and other symptoms that respond to airway-relaxing drugs, known as bronchodilators.
But could there be a link? A recent study by researchers in Australia found that more than 40% of children with severe asthma developed COPD by the age of 50—a 32-fold higher risk compared to asthma-free children. The researchers followed nearly 200 children beginning at age 7.
"This certainly raises the point that early and aggressive treatment of asthma may indeed prevent the development of COPD later in life," says Robert Wise, MD, a professor of environmental health sciences at the Johns Hopkins University School of Medicine, in Baltimore.
But it's too early to be sure, Dr. Wise says.
What is COPD?
Experts believe that in some people, asthma—particularly severe asthma—raises the risk of COPD later in life. Asthma, an inflammatory condition, can thicken the walls of lung airways and narrow air passages, a process known as remodeling.
"I suspect that this remodeling of the airway may be part of what leads to fixed airflow obstruction in COPD," says Dr. Wise.
COPD includes two conditions, emphysema and chronic bronchitis, and is often, but not always, caused by smoking. About 1 in 4 long-term smokers will get COPD, if they live long enough. Other causes of COPD include secondhand smoke, workplace exposure to dust and pollutants, and a rare genetic condition. All of these may damage the lungs and dramatically speed up a process that happens in all people—a loss of lung function with age.
Next Page: Asthma may accelerate loss of lung function
[ pagebreak ]"Everyone loses a little lung function every year," notes Dennis E. Doherty, MD, a professor of pulmonary medicine at the University of Kentucky College of Medicine, in Lexington.
If your lung function is low to begin with (due to exposure to tobacco smoke or pollutants, for instance), you could hit that critical point in your lifetime, Dr. Doherty explains. It's possible that severe, untreated asthma might also reduce lung function, although researchers aren't sure.
Unlike people with asthma, those with COPD never fully regain normal lung function with treatment and, instead, progressively struggle to catch their breath as they age. And drugs that help asthma—bronchodilators, inflammation-fighting steroids—are much less effective for COPD.
COPD misdiagnosed as asthma
Unfortunately, the significant resemblance between the symptoms of the two diseases often causes one to be mistaken for the other, which can lead to improper treatment. A study published in the Journal of Asthma in 2006 estimated that more than 50% of people with COPD are misdiagnosed with asthma.
However, the two conditions do sometimes co-occur. Experts estimate that as many as 20% of people with COPD actually have asthma too.
"Asthma is a much more socially acceptable diagnosis," says Dr. Wise, pointing to the strong link between smoking and COPD as a source of COPD's bad reputation. The stigma associated with COPD can make it even more difficult for doctors to disentangle diagnoses of COPD and asthma, he adds.
This stigma may be especially important for women. In a group of people with identical medical histories and symptoms, research suggests, the men are more likely to be diagnosed with COPD and the women are more likely to be diagnosed with asthma. As it turns out, more women than men actually die from COPD.
There may be a gender divide in asthma as well. A 2008 study in the American Journal of Respiratory and Critical Care Medicine suggested that boys are more likely than girls to outgrow asthma when they reach puberty.
But many questions remain regarding the possible connection between asthma and COPD. "We still have a lot to know about the transition between childhood asthma and adult COPD," says Dr. Wise, "just how it takes place and how to prevent it."
Next Page: Treating asthma is key
[ pagebreak ]Treating asthma is key
While research is ongoing, it's important to follow children with asthma into adulthood and manage their symptoms well along the way, says the lead researcher of the Australian study, Andrew Tai, MD, of the Women's and Children's Hospital, in Adelaide.
In the study, which Dr. Tai presented at the American Thoracic Society's 2010 International Conference, only children with severe asthma were at an increased risk of COPD. No increased risk was seen among children with mild asthma, a group that often outgrows the condition.
Children with severe symptoms tend to have allergies, and carry their wheeze into adulthood. In fact, many doctors probably don't see such severe cases anymore, says Dr. Tai. During the 1960s, today's mainstay asthma medications—inhaled corticosteroids and other anti-inflammatory drugs—were not yet available.
Could some of these COPD cases have been prevented if children had been more rigorously treated? And could current asthma sufferers step up treatment to ward off the disease?
Dr. Wise says that the evidence is not yet solid enough to say. But if this link turns out to be real, then many patients today are still missing out on the COPD protection. "We know that about 50% of patients with asthma, including children, have inadequately controlled asthma," he notes. "And we know that at least half of the prescribed steroids never get filled."
Dr. Tai agrees. His study suggests that children with severe asthma don't necessarily experience faster decline in lung function later in life. Instead, their lung development may be compromised early on, which suggests that COPD could be prevented with better childhood asthma treatment.
For now, researchers do know that cigarette smoking may be a risk factor for developing COPD, not just a trigger for asthma symptoms. Sadly, about 1 in 5 kids with asthma end up smoking later in life, according to research by Dr. Wise.
Even though smoking is dangerous for anyone, it is particularly so for people with asthma.
"While not everyone who smokes is going to get COPD, this allows us to target resources towards a particularly vulnerable population," says Dr. Wise.