Reduced physical activity in COPD not just disease related

Researchers from the Netherlands have shown that physical activity in patients with chronic obstructive pulmonary disease (COPD) is influenced by both physical and psychosocial factors.

And, as disease progressed, physical activity was more strongly affected by disease-specific factors, leading the authors to suggest that sedentary lifestyles should be addressed in the early disease stages to prevent later inactivity.

The team, from the University of Groningen, analyzed the 24-hour physical activity of 113 COPD patients using a triaxial accelerometer over the course of 1 week (minimum: 4 full days). The patients had a range of disease severity with 26.5% Global Initiative on Chronic Obstructive Lung Disease (GOLD) stage I, 26.5% stage II, 28.3% stage III, and 18.6% stage IV.

Physical activity (locomotion time and number of steps per day) was similar in GOLD stages I and II but significantly differed between all the other stages, being lowest in those in stage IV. Locomotion time also significantly differed in all quartiles of the BODE index (combining body mass index, forced expiratory volume in 1 second, modified Medical Research Council dyspnea index, and 6-minute walk distance) as did steps per day in quartiles III and IV.

When the researchers compared patients in GOLD stages I and II to those in stages III and IV they found differences in the factors influencing activity. Whereas in those with mild-to-moderate disease, physical activity was independently associated with self-efficacy and season (lower in autumn/winter vs spring/summer), in those with severe and very severe disease it was linked to residual volume, dyspnea severity, leg muscle function, and the use of long-term oxygen therapy.

Writing in the Archives of Physical Medicine and Rehabilitation, authors Nick ten Hacken and colleagues note that, “[a]pparently, disease symptoms are the main limiting factor for physical activity in patients with more severe COPD.” In patients with more mild disease, whose activity is less restricted by disease, they suggest that physicians explore alternative activities in case of bad weather in the winter months.

The team also reports that, contrary to their expectations, sitting time did not significantly differ between the groups, according to GOLD stage, although patients in stages III and IV sat, on average, 40 minutes longer per day than those in milder stages.

“This could be clinically relevant because longer sitting time has been found to be associated with an increased risk of mortality, even independent of leisure time physical activity,” they comment, adding that promoting breaks in sitting time could be beneficial.

The team concludes: “Because sitting time or physical inactivity has not been thoroughly investigated in patients with COPD, we believe that future studies on physical activity should investigate this aspect as well.”

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