Determinants of Physical Activity in Patients with Chronic Obstructive Pulmonary Disease: A 5-Year Prospective Follow-Up Study

BACKGROUND: Although many studies examined determinants of physical activity in patients with chronic obstructive pulmonary disease (COPD), most were cross-sectional and focused on single determinants only. OBJECTIVES: The aim of this study was to determine how COPD patients' physical activity changes over time and to identify the determinants of physical activity using multivariable and longitudinal methods. METHODS: In a prospective cohort study, 409 primary care patients with COPD in the Netherlands and Switzerland were followed for up to 5 years. Physical activity was assessed at baseline and every 6 months using the Longitudinal Aging Study Amsterdam Physical Activity Questionnaire (LAPAQ) adapted to a 0- to 23-point scale. We studied the associations between determinants at baseline and patients' long-term physical activity levels using linear mixed models. RESULTS: Unadjusted analysis showed an overall gradual decline in physical activity (0.22 points of the LAPAQ scale every 6 months, 95% CI: 0.17-0.28; p < 0.001). In multivariable analyses, baseline determinants that were independently associated (p ≤ 0.05) with lower long-term physical activity levels included (starting from coefficients with the smallest p value) lower exercise capacity, older age, working, more smoking pack-years, more fatigued, male sex, lower educational levels, previously not in fitness programs, more depressed, lower lung function, lower overall health status, and more prescription drug use. CONCLUSIONS: We found that physical activity of COPD patients may decline more than reported in the healthy elderly. Longitudinal analysis identified independent determinants of physical activity, which allows the identification of patients having low physical activity levels and who may benefit from physical activity interventions.