And several small studies have suggested that the distance a patient can cover in six minutes may be an important indicator of overall health.
Less is known, however, about where the danger zones may lie for people who take the test.
Walking Speed and COPD
The study of 2,110 patients was presented at the 2011 American Thoracic Society International Conference in Denver. It found that people with moderate to severe COPD who couldn't walk at least 357 meters in six minutes -- that's most of the way around a standard high school track -- were at higher risk for hospitalization. Participants who couldn't walk at least 334 meters were at increased risk of death over the three-year study period.
Experts who weren't involved with the research, however, say that patients and doctors shouldn't get too hung up on the specific distances involved.
What's probably more important about the study, says Kevin K. Brown, MD, vice chairman of the department of medicine at National Jewish Health in Denver, is that it is a reminder that COPD goes beyond the lungs.
"It confirms the importance of thinking about COPD as a systemic disease," Brown says. He says it shows that exercise tests to see how well patients can move and get around are important.
Patients in the study, who were mostly men in their 60s, saw a steady decline in their walking speed with each passing year.
"There is a gradual decline in six-minute walk distance of about 5 meters per year, in particular, in patients with a limited ability to breathe easily," says study researcher Martijn Spruit, PhD, scientific advisor at the Center of Expertise for Chronic Organ Failure (CIRO) in Horn, Netherlands.
Spruit says that walking speed can also improve, especially if people participate in rehabilitation.
In the same study, Spruit says, "the treatment gains following exercise-based pulmonary rehabilitation programs, including aerobic and strengthening exercises, showed a mean improvement of 50 meters per year." Those gains greatly outweigh the average declines.
Risks for COPD
The biggest risk for getting COPD is exposure to cigarette smoke. Other risks include exposure to air pollution, a family history of lung disease, or a childhood history of lung infections.
COPD was the third most common cause of death in Americans in 2007, according to the CDC.