COPD: Physical Activity Decreases Regardless of Severity

Susan London

June 19, 2015

Patients with chronic obstructive pulmonary disease (COPD) become less physically active over time, no matter how severe their disease is initially, and this trend is associated with worsening airflow obstruction and health status, according to a longitudinal cohort study published online May 28 in the American Journal of Respiratory and Critical Care Medicine.

A team led by Benjamin Waschki, MD, from the Pulmonary Research Institute at LungenClinic Grosshansdorf in Germany, measured physical activity and a variety of pulmonary and general health outcomes during a 3-year period in 137 patients who had COPD and 26 patients with chronic bronchitis who were considered to be at risk for the disease at the time.

During follow-up, the patients experienced reductions in a variety of measures of physical activity assessed with a multisensory armband; on average, they had an adjusted annual decline of 393 steps walked per day, 76 kcal in total daily energy expenditure, and 0.04 units in daily physical activity level. These changes were independent of the baseline disease severity as reflected by Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage.

The decline in physical activity level was significantly associated with increasing airflow obstruction, indicated by falling forced expiratory volume in 1 second, and worsening health status, indicated by rising total scores on the St. George's Respiratory Questionnaire. In contrast, the decline in physical activity level was not significantly associated with changes in exercise capacity (as assessed with the 6-minute walk distance), muscle mass, or systemic inflammation (as ascertained from levels of fibrinogen and high-sensitivity C-reactive protein).

Overall, 24% of evaluable patients had sustained physical inactivity, meaning they had a value of less than 1.40 units at both baseline and follow-up. Relative to peers who got at least some physical activity, these patients had a greater decline in exercise capacity, with a difference of 17 m/year on the 6-minute walking distance, and in muscle mass, with a difference of 0.87 kg/year in fat-free mass. These associations were independent of the severity of airflow obstruction assessed from forced expiratory volume in 1 second.

"[A] sustained low level of physical activity is related to a progression of exercise intolerance and muscle depletion in all patients with COPD," the authors write. "Interestingly, sustained physical inactivity was not associated with a progression of airflow obstruction or a worsening of health status."

"Recent guidelines advocate regular physical activity for patients with COPD at all severity stages despite the fact that little COPD-specific evidence exists.... Our data clearly support this recommendation, because a sustained low level of physical activity over time is associated with an accelerated progression of exercise intolerance and muscle depletion," the investigators note. "Furthermore, we have demonstrated that physical activity decreases early in the course of the disease, along with a worsening of lung function and health status."

The study excluded patients who died during follow-up, the authors note. "For those deceased patients, physical inactivity was already shown to be the strongest predictor of mortality.... Therefore, the role of physical inactivity in disease progression might even be underestimated in the current analysis," the investigators maintain.

For former cross-sectional analyses, some baseline measurements were supported by an unrestricted research grant from AstraZeneca Germany. The authors have disclosed no other relevant financial relationships.

Am J Respir Crit Care Med. Published online May 28, 2015. Abstract

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