Interventions to modify physical activity in patients with COPD: where do we go from here?

Assessing participation in physical activity as an outcome in patients with chronic obstructive pulmonary disease (COPD) has received growing attention in recent years [1, 2]. This can be explained both by an increased recognition of health effects associated with physical (in)activity and by the high prevalence of physical inactivity in patients suffering from COPD. Benefits of physical activity in the general population and in the elderly are well documented and include a reduction in cardiovascular disease, type 2 diabetes, cancer, dementia, risk of falling and all-cause mortality [3-5]. Physical activity has also been associated with better preservation of bone mass, higher quality of life and improved cognitive function [4, 5]. Interestingly the protective effects of (increases in) physical activity on (cardiovascular) morbidity and mortality have been shown to be present independent of physical fitness levels [6]. Inactivity has been shown to be highly prevalent in patients with COPD [7]. Duration of activities has been shown to be slightly more reduced than the intensity of activities (57% and 75%, respectively, of values observed in healthy controls) [8]. A reduction in physical activity is already present early in the disease and worsens with progressing disease severity [9, 10]. Even (ex-)smokers unaware of their airflow limitation show reductions in physical activity when compared with (ex-)smokers without airflow limitation [11]. When compared with other chronic conditions, such as diabetes and rheumatoid arthritis, inactivity is more prevalent in patients with COPD [12]. The association of physical activity with health outcomes specifically relevant to patients with COPD has also been studied in recent years. It has been demonstrated that increased participation in physical activity is associated with reduced risks for hospital admission and mortality [13]. From data collected in preclinical patients with COPD (i.e. (ex-)smokers unaware of their airflow limitation) it was concluded that inactivity and smoking, rather than the disease COPD as such, were the main risk factors for developing comorbid conditions (cardiovascular, metabolic and musculoskeletal disease) [14]. Patients progressively decrease physical activity over time [15]. Some data are also available on the impact of changes in activity behaviour on health status. Esteban et al. [16] showed that patients who increased their physical activity over a 2year follow-up showed a decrease