Physical activity decreases over time in COPD patients

Physical activity decreases substantially over time in patients with chronic obstructive pulmonary disease (COPD) at all levels of severity, according to a German study published recently in the American Journal of Respiratory and Critical Care Medicine.

This decline in physical activity is accompanied by a worsening of lung function and health status, and sustained physical inactivity is associated with progression of both exercise intolerance and muscle depletion.

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In a prospective cohort study, lead author Benjamin Waschki, MD, and colleagues at LungenClinic Grosshansdorf in Germany, measured physical activity (multisensory armband over one week), airflow obstruction (forced expiratory volume in one second), health status (St. George’s Respiratory Questionnaire), exercise capacity (six-minute walk distance), muscle mass (fat-free mass by bioelectrical impedance analysis), and systemic inflammation (fibrinogen and high-sensitivity C-reactive protein)  over a three-year period in 137 patients with COPD and 26 patients with chronic bronchitis and normal spirometry.

Independent of the severity of COPD at baseline, steps per day, total daily energy expenditure, and daily physical activity level (PAL) decreased by 393, 76 kcal, and 0.04 per year, respectively. This decline in PAL was significantly associated with an increase in airflow obstruction (shown by a decline in FEV₁) and an increase in total score on the St. George’s Respiratory Questionnaire, which measures the impact of obstructive airway disease on overall health, daily life, and perceived well-being.

Independent of FEV₁ measurements, sustained physical inactivity was associated with greater declines in 6-minute walk distance results and fat-free mass compared to some level of physical activity.

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This is the first study that longitudinally analyzed objectively measured physical activity in relations with other important disease components over time.

“Physical activity decreases substantially across all severity stages of COPD over time,” says Waschki in an e-mail to Medical Economics. “This decline is paralleled by a coexisting worsening of airflow obstruction and health status. In addition, a sustained low level of physical activity over time is associated with an accelerated progression of exercise intolerance and muscle depletion.”

These findings support the theory that physical inactivity occurs as an early feature within the downward disease spiral in COPD and may causally contribute to muscle depletion and exercise intolerance, according to the researchers.

“The maintenance of physical activity may influence disease progression positively,” says Waschki. “Physical inactivity is an important factor in COPD which is relevant even early in the course of the disease and which seems to contribute to the worsening of other disease characteristics.”