Chronic obstructive pulmonary disease, or COPD, is the fourth leading cause of death in the United States, killing more than 100,000 people a year. It's actually a blanket term for emphysema, chronic bronchitis, and other lung ailments that block air flow, are not easily reversed, and tend to strike during middle or old age. That makes COPD distinct from asthma, which is characterized by inflammation, usually develops in childhood, and usually resolves itself or can be treated with medication. Yet though physicians have considered these diseases to be different, they noticed that they sometimes show similar symptoms as they progress—later in the course of their disease, for example, asthmatics may eventually have attacks that are not treatable. Researchers at the University of Arizona wanted to examine more closely the relationship between asthma and later development of COPD.

What the researchers wanted to know: Could there be some connection between asthma and a subsequent development of COPD?

What they did: Scientists followed 3,099 adults for 20 years. The patients were initially evaluated for lung problems; 192 had active asthma, 156 had been diagnosed with asthma but had no current symptoms, and the rest didn't have asthma. None had COPD. The group was evaluated via surveys and lung function tests a dozen times over the next two decades.

What they found: People with active asthma were 10 times more likely to later develop chronic bronchitis, 17 more times likely to have emphysema, and 12.5 times more likely to meet the criteria for COPD than nonasthmatics. There was no extra risk for the patients who initially reported inactive asthma.

What it means to you: If you have active asthma, you may be at risk of developing more serious symptoms associated with COPD later in life. The way to forestall this, the authors say, may be to avoid risk factors like tobacco smoke (yours or someone else's) and air pollution. Aggressively treating asthma with anti-inflammatories may also forestall the symptoms of COPD.

Caveats: This study was based on symptoms, not a precise clinical diagnosis of COPD or asthma. It is not possible to determine whether asthma is leading to COPD or whether asthmatic symptoms simply worsen over time. In addition, the study's subjects were all Caucasian; it's not known whether other races would show similar results.

Find out more: The National Lung Health Education Program has information about both diseases at http://www.nlhep.org/.

Read the article: Silva, G.E. et al. "Asthma as a Risk Factor for COPD in a Longitudinal Study." Chest. July 2004, Vol. 126, No. 1, pp. 59–65.

Abstract online: http://www.chestjournal.org