Activity promotion: a paradigm shift for chronic obstructive pulmonary disease therapeutics

Many patients with chronic obstructive pulmonary disease (COPD) lead unsatisfying, sedentary existences, worn down by years of dyspnea and exacerbations. A downward spiral links progressive inactivity to accelerating disability and premature mortality. Indeed, cross-sectional COPD studies have demonstrated that inactivity is a potent predictor of early death. It should be considered a high priority for future COPD therapies to ameliorate inactivity. A necessary prerequisite to this endeavor is development of techniques to accurately assess activity levels. Development of questionnaires or, arguably more importantly, instrumentation for objective measurement of activity is a priority. There is a tendency to equate exercise intolerance with inactivity. Although, in a population, the two are correlated, higher exercise tolerance is only permissive of higher activity. It is plausible that, in reported correlations of measures of exercise tolerance with long-term outcomes, exercise tolerance is simply a proxy variable for activity level. Interventions have been identified that improve exercise tolerance in COPD. Do these interventions also increase activity levels? To date, evidence is mixed. No studies have appeared demonstrating that bronchodilator therapy or provision of lightweight ambulatory oxygen supplies increase activity level. Nine studies have appeared in which the ability of pulmonary rehabilitation to increase activity levels, objectively assessed by activity monitors; four of nine have demonstrated significantly increased activity levels. Future efforts should strive to isolate strategies that improve activity, perhaps coupling interventions permissive of improved exercise tolerance with behavior modification approaches that empower lifestyle modification. In particular, pulmonary rehabilitation seems ripe for augmentation with scientifically based strategies for activity promotion.