MONDAY, July 12, 2004 (HealthDayNews) -- Asthma just might pave the way for the development of chronic obstructive pulmonary disease (COPD), a much more serious lung condition.
As a matter of fact, people with asthma are 12.5 times more likely to develop COPD later in life, suggests a study in the July issue of Chest.
"For many years, there has been an attempt to separate COPD and asthma as distinct entities with not that much in common. But, as you get into obstructive airway diseases [in older people], that distinction becomes more difficult to make. If you start out with asthma, many of those asthmatics will later be given a diagnosis of COPD," said study co-author Dr. Robert Barbee, professor emeritus at the University of Arizona College of Medicine in Tucson. "The question is, is it appropriate to look at them as distinct, or is there a common basis for obstructive lung disease?"
More than 22 million adults in America have asthma. COPD is the term used to describe emphysema and chronic bronchitis. Three million people have been diagnosed with emphysema, while another 11.2 million have chronic bronchitis, according to the National Center for Health Statistics. COPD is the fourth leading cause of death in the United States.
Smoking is one of the biggest risk factors for the development of COPD, though Barbee said less than 20 percent of all smokers develop COPD, suggesting there are other important risk factors as well.
For this study, the Arizona researchers followed more than 3,000 people from Tucson for up to 20 years. Throughout that study period, the volunteers were asked to complete 12 questionnaires regarding their respiratory health and underwent a lung function test called a spirometry as many as 11 times.
Most of the study volunteers -- 2,751 people -- reported no asthma. One hundred and fifty six said they had had asthma in the past, but it was now inactive, and 192 people had active asthma.
Overall, people with active asthma had a 12.5 times greater risk of COPD. The risk of emphysema was 17 times greater for people with active asthma than for people without asthma. People with active asthma faced a 10 times greater risk of chronic bronchitis than those who didn't have asthma.
The researchers also found increased age and smoking status were also linked to the development of COPD. They found no link between past asthma and COPD.
"Our study shows a strong link between asthma diagnosis and the development of COPD. It is possible that factors such as smoking and repeated episodes of acute bronchitis may facilitate the evolution of asthma into COPD, but the process by which asthma and COPD become co-morbid conditions is not clear," study author Graciela Silva, a doctoral candidate, said in a statement.
Dr. Michael Iannuzzi, chief of pulmonary, critical care and sleep medicine at Mount Sinai Medical Center in New York City, said it's important to note that just because this study found an association between these conditions, it does not mean that asthma causes COPD.
"Whenever you find an association, it doesn't prove cause and effect," he said. "One still needs to discover the mechanisms of why the association exists."
He said this study's size and duration were impressive, but noted the study is limited because it relies on people self-reporting whether they have active asthma. He said some people who think they have asthma may, in fact, have early COPD.
Iannuzzi said the single most important thing anyone can do to help prevent COPD is to not smoke, or stop smoking if you're already a smoker. He said that may be even more important if you have a history of allergies or asthma.
He said that smokers and those with a history of allergies or asthma should ask their physicians to routinely screen their lung function. Iannuzzi believes spirometry should be used as a screening tool as routinely as blood pressure or cholesterol testing is. That way, he said, treatment can begin early if there's a problem, and for smokers, an objective test showing them how smoking is affecting their body could be a way to motivate them to stop smoking.
More information
To learn more about chronic obstructive pulmonary disease, visit the National Heart, Lung, and Blood Institute.
