Better evidence needed for relationship between exercise and COPD

By Laura Cowen, medwireNews Reporter

Researchers call for high-quality studies investigating the relationship between physical activity and chronic obstructive pulmonary disease (COPD) after their systematic review found the level of evidence to be poor.

Although Judith Garcia-Aymerich (Centre for Research in Environmental Epidemiology, Barcelona, Spain) and colleagues established that physical activity is consistently associated with mortality and exacerbation, evidence about determinants of physical activity, including the impact of treatment, was lacking, they report in Thorax.

Garcia-Aymerich and team reviewed 86 studies assessing associations between physical activity and its determinants and/or outcomes in patients with COPD: 59 focused on determinants, 23 on outcomes and four on both.

The majority of the studies were cross-sectional (n=36) and only half (n=43) measured physical activity using a direct method such as an accelerometer or pedometer.

The studies measuring clinical and functional determinants of physical activity showed that hyperinflation, exercise capacity, dyspnoea, previous exacerbations, gas exchange, systemic inflammation, quality of life and self-efficacy were consistently related to physical activity level. However, these findings were often based on evidence graded as low- or very low-quality due to its cross-sectional nature and lack of adjustment for confounders.

The researchers found that a large proportion of the studies (n=21) investigated the effect of exercise training on physical activity, but the results were inconsistent and the quality of evidence was again low because many did not include a control group or included a control group without randomisation.

Only three studies tested the effect of pharmacological treatment on physical activity, with inconsistent results and “several methodological flaws” that resulted in quality of evidence being rated as very low.

In terms of COPD outcomes, Garcia-Aymerich et al found that, overall, the quality of evidence was better than that for determinants, despite there being fewer studies.

Indeed, low levels of physical activity were consistently associated with a reduced risk of COPD exacerbations and mortality, based on moderate quality evidence.

Physical activity level was also associated with dyspnoea, health-related quality of life, exercise capacity and forced expiratory volume in 1 second, but the findings were inconsistent and based on cross-sectional studies with low- to very low-quality evidence.

Given the generally poor quality of evidence observed in this review, the researchers conclude that “[t]he research community should make an effort to conduct prospectively planned cohort studies and randomised trials to provide a stronger evidence base for determinants and outcomes of physical activity and for developing recommendations for or against treatments in clinical guidelines.”

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