Chronic obstructive pulmonary disease (COPD) affects both pulmonary and non-pulmonary systems and results in a wide range of physical functional limitations in sufferers. This study is an attempt to characterise the impact of COPD on non-pulmonary function.

One thousand and two patients from the Kaiser Permanente Medical Care Program (KPMCP) aged 40–65 years who met the criteria for a diagnosis of COPD and who had also received two or more prescriptions for COPD-related illness in the previous 12 months were recruited. The study participants were matched by age, sex and race with a reference group of 302 patients from the KPMCP who did not meet either of the criteria for a COPD diagnosis. Subjects participated in a series of validated assessments of physical function including short physical performance battery, 6-minute walk test and skeletal muscle strength testing. In addition, semi-structured interviews were used to provide information on self-reported functional limitation.

Not only was pulmonary function found to be significantly poorer in the study group, the patients with COPD were also found to have significantly greater deficits in lower extremity functioning, exercise performance, muscle strength and had a higher rate of self-reported functional limitations. These deficits remained after potential confounding factors were accounted for—such as age, sex, race, height, educational attainment and cigarette smoking.

The authors conclude that the functional limitations found are specifically attributable to COPD; however, the impact of any co-morbidities is unclear. Interestingly, the majority of patients with COPD studied were GOLD stage 0–2 and therefore it seems that systemic manifestations have an impact even in mild patients. The age range of the participants means that the applicability of the study findings to those aged >65 years is uncertain and most likely underestimated.

▸ Eisner MD, Blanc PD, Yelin EH, et al. COPD as a systemic disease: impact on physical functional limitations. Am J Med 2008;121:789–96.