Determinants and outcomes of physical activity in patients with COPD: a systematic review

Abstract

Background: The relationship between physical activity, disease severity, health status and prognosis in patients with COPD has not been systematically assessed. Our aim was to identify and summarise studies assessing associations between physical activity and its determinants and/or outcomes in patients with COPD and to develop a conceptual model for physical activity in COPD.

Methods: We conducted a systematic search of four databases (Medline, Embase, CINAHL and Psychinfo) prior to November 2012. Teams of two reviewers independently selected articles, extracted data and used the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) to assess quality of evidence.

Results: 86 studies were included: 59 were focused on determinants, 23 on outcomes and 4 on both. Hyperinflation, exercise capacity, dyspnoea, previous exacerbations, gas exchange, systemic inflammation, quality of life and self-efficacy were consistently related to physical activity, but often based on cross-sectional studies and low-quality evidence. Results from studies of pharmacological and non-pharmacological treatments were inconsistent and the quality of evidence was low to very low. As outcomes, COPD exacerbations and mortality were consistently associated with low levels of physical activity based on moderate quality evidence. Physical activity was associated with other outcomes such as dyspnoea, health-related quality of life, exercise capacity and FEV1 but based on cross-sectional studies and low to very low quality evidence.

Conclusions: Physical activity level in COPD is consistently associated with mortality and exacerbations, but there is poor evidence about determinants of physical activity, including the impact of treatment.

Keywords: COPD Exacerbations; COPD epidemiology; Exercise.

Figure 1

Flow diagram of process of systematic literature search. *Details for reason for exclusion in online supplementary table S1.

Figure 2

Graphical illustration of the individual study effects of physical activity on reduced risk of exacerbations. Pitta 2006 was excluded from the graph because it did not provide a risk ratio.

Figure 3

Graphical illustration of the individual study effects of physical activity on reduced risk of mortality.

Figure 4

Conceptual model of physical activity in patients with COPD. Grading was done separately for each individual determinant/outcome (table 2). Variables of the same category sharing the same confidence rating are grouped together in this figure for clarity. Socio-demographic, lifestyle and environment, and some clinical variables (FEV₁, body mass index, emotional status and comorbidities) do not show consistent effects on physical activity. The association between other clinical and functional determinants and physical activity such as hyperinflation, exercise capacity, dyspnoea, previous exacerbations, gas exchange, systemic inflammation, quality of life and self-efficacy is consistent across studies, but lacking directionality because mostly it is based on cross-sectional studies. Studies on pharmacological and non-pharmacological treatments as determinants of physical activity are all longitudinal and thus, by design, provided a basis for a clear direction of the associations. But the results are inconsistent with some treatments showing an increase in physical activity and some showing no effect. Regarding the outcomes, only COPD exacerbation and mortality show consistent effects with clear directionality and based on moderate quality evidence.