LAUSR

To the Editors: We read with great interest the study of Valeiro et al. regarding the promotion of physical activity after hospitalization for chronic obstructive pulmonary disease (COPD) exacerbation in the latest issue of Respirology. Since pulmonary rehabilitation is not accessible to a great proportion of COPD patients, investigating other treatment options to enhance a non-sedentary lifestyle is of great value. The fact that the current study is a randomized control trial (RCT), further emphasizes its value, since RCTs are scarce in this field. The calculated sample size of the trial was enough so that differences in step count to be detected. However, it is quite surprising that no other physical activity parameter (i.e., standing time, sedentary time, walking time, light or moderate physical activity) differed between the groups. The authors have correctly stated that the size of the population was relatively small and empowered only to detect differences in step count. However, more variables have to be taken under consideration. Micro-and macroenvironment in the area of living is an important determinant of physical activity, with high neighbourhood walkability, high street connectivity, and proximity and availability of transport system being positively associated with daily physical activity. More over, weather conditions may also affect daily physical activity; rainy and overcast days have been associated with lower stepcount, while sunny and hotter days with higher stepcount. The 6-minute walking test (6MWT) and the COPD assessment test (CAT) score were two other variables that did not differ between the groups. Small sample size may again be the reason for that, since the use of pedometers has been associated with increased 6MWT and CAT improvements in a larger case–control study, compared to activity encouragement only. Irrespective of the improvement of other exercise capacity measures, enhancement of physical activity per se has proven largely beneficial for COPD patients, as subjects with higher physical activity experience less acute exacerbations and have lower mortality than those with lower physical activity levels. Since the adoption of a more active lifestyle may be influenced not only by the structure of the intervention, but also by several microand macro-environmental factors, larger RCTs are needed, in order to assess the impact of these factors on various treatment modalities and how these factors can be controlled.