The association between co-morbidities and physical performance in people with chronic obstructive pulmonary disease: A systematic review

A systematic review was conducted to examine the association between co-morbidity and physical performance in people with chronic obstructive pulmonary disease (COPD). MEDLINE, EMBASE, CINAHL, SCOPUS and Cochrane Central Register of Controlled Trials were searched from inception to end-February 2013, using keywords 'COPD', 'exercise', 'physical activity', 'rehabilitation', 'co-morbidity' and individual co-morbid conditions. Studies reporting associations of co-morbidities in COPD with at least one objective measure of physical performance were included. Study quality was appraised using the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist. Nine studies met inclusion criteria. Mean (standard deviation (SD)) STROBE score was 16 (3) (maximum score = 21). Four studies examined anxiety as a co-morbid condition; three examined depression; two examined obesity and two examined a range of conditions. Reduced physical performance was associated with higher Charlson score (odds ratio (OR) = 0.72, 95% confidence interval (CI) = 0.54-0.98), metabolic disease (OR = 0.58, 95% CI = 0.49-0.67), anxiety (OR = 0.37, 95% CI = 0.23-0.59) and osteoporosis (OR = 0.28, 95% CI = 0.11-0.70). Depression had minimal association with physical performance but was associated with higher dropout rates from pulmonary rehabilitation programmes. Obesity was negatively associated with baseline physical performance but not with change from an exercise intervention. The presence of co-morbid conditions in people with COPD may negatively affect physical performance and should be identified and accounted for analysis of interventions.