@ERSpublications From observational studies, it is now clear that physical inactivity is linked with poor outcome in COPD http://ow.ly/AJ7mFArguably, three outcome categories are of greatest importance to chronic obstructive pulmonary disease (COPD) patients, their families and their caregivers: health-related quality of life (including symptom burden); hospitalisations and other forms of healthcare utilisation; and, of course, mortality. Lower levels of baseline physical activity are not only prevalent in patients with COPD [1, 2], they are associated a negative impact in each of these three outcome categories [3][4][5].Of considerable importance to healthcare professionals, increases in physical activity appear to predict enhanced health-related quality of life and reduced hospitalisations. For example, in an analysis of 391 patients with COPD who had physical activity and health-related quality of life assessments at baseline and 5 years later [6], those who increased or maintained their high levels of physical activity had clinically meaningful improvements in quality of life. In contrast, those who stayed at a low level or decreased their physical activity had a worsening in this outcome. From one perspective, this comes close to a tautology, as physical function impairment and distressing symptoms associated with physical activity are prominent components of health-related quality of life questionnaires. With respect to healthcare utilisation, a longitudinal analysis of COPD patients over 5 years demonstrated that the change in physical activity over the first 2 years significantly predicted hospitalisations 3 years later: those without regular physical activity, those who maintained a low level of physical activity or those who decreased their physical activity were at significantly greater risk of being hospitalised than those with higher levels of physical activity [7].The reanalysis of the very large Copenhagen City Heart Study database by VAES et al. [8], reported in this issue of the European Respiratory Journal, adds new and important information by relating changes in physical activity to mortality risk in COPD. We already know there are often strong associations between low levels of physical and mortality. For instance, all-cause mortality risk is higher in patients with coronary artery disease and cancer who have lower levels of physical activity [9,10]. This also holds true for COPD: using Copenhagen City Heart Study data, demonstrated that, in participants meeting spirometric criteria for COPD, those with very low levels of self-reported physical activity had a higher risk of hospitalisation and mortality over approximately the next 17 years than those who participated in regular physical activity. This negative relationship between physical activity and poor outcome remained in their model even after controlling for potential relevant confounding factors. This study provides strong evidence that physical inactivity is bad for individuals with COPD. Subsequent studies by WASCHKI et al. [4] a...