Physical activity and comorbidities in patients with COPD

Over the past two decades, the prevalence of a physically inactive lifestyle has increased markedly in the general population. This reduction in daily physical activity is even more pronounced in chronic disease populations, such as Chronic Obstructive Pulmonary Disease (COPD). In addition, physical inactivity is not only linked with COPD but also can act as a potential risk factor for the presence of co-morbidities. Since physical inactivity and the presence of co-morbidities have a negative impact on several health-related outcomes (hospital admission, health care costs and survival), the objective measurement with a valid and usable activity monitor and the early detection of the inactive COPD patients are two important issues that were focused in the present PhD-project.A systematic literature review looked at 134 papers validating 40 activity monitors. We concluded that triaxial and multisensor devices tend to be the more valid monitors. Most validation studies were performed in healthy adults (88% of the studies), only few looked at patients with chronic diseases (12% of studies). Hence, we selected six activity monitors for prospective validation in COPD in both a laboratory setting and a field setting (not part of the PhD thesis). Based on a set of pre-defined validation and usability criteria, it is concluded that the Dynaport MiniMod, the Actigraph GT3X and the SenseWear Armband were considered as valid and usable activity monitors in COPD. An active lifestyle increases the chances to a healthy life . In order to know whether a subject is active or not, clear physical activity guidelines/targets should be available. We demonstrated that moderate intense physical activities (MVPA) varies depending on the selected physical activity guideline/target with lowest values for age-specific cut-offs. The observation of a reduced exercise capacity may lead to an overestimation of MVPA when selecting a relative METs cut-point (corresponding to 50% of VO2 reserve). Accelerometry measured MVPA (non-bouts) of 80 min*day-1 corresponds to the current recommendation of 30 minutes of MVPA*day-1 (in bouts of at least 10 minutes) and is valid to discriminate active from inactive subjects. This finding indicates that caution is needed when MVPA data are analyzed and interpreted in bouts or not.In the cross-sectional studies on activity profiles of patients in the preclinical stages of COPD, we found that the reduction in physical activity starts early in the disease, even when subjects are just diagnosed as having COPD, especially in those with mild symptoms of dyspnea, lower levels of diffusion capacity and lower levels of exercise capacity. The prevalence of pre-morbid risk factors and co-morbid diseases in this population was significantly higher compared to age- and gender-matched never-smokers, but similar to smoking controls not suffering from COPD. Finally, we showed that co-morbidities pool together (especially cardiovascular and musculoskeletal disease) and that physical inactivity was independently associated with thepresence of co-morbidities. Therefore, symptomatic COPD patients, those with reduced diffusion capacity and those with reduced exercise capacity should be targeted for physical activity enhancing interventions.status: publishe