Functional performance in patients with COPD: association with treatment regimen, GOLD group, lung function, and symptom burden in a cross-sectional study.

Background: Data suggesting that low physical activity levels are associated with increased mortality and exacerbations in patients with COPD have led to increasing interest in the role of physical activity in COPD. This study evaluated self-reported functional performance, a measure of physical activity impairment, according to current treatment regimen, lung function, symptoms, and Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2017 groups in a large sample of patients with COPD. Methods: This multicenter, cross-sectional, observational study (study identifier: D5970R00003) included patients with COPD (≥40 years) in the USA. A self-completion questionnaire captured demographics and patient-reported outcomes, including the Functional Performance Inventory-Short Form (FPI-SF). Diagnosis and treatment history (including spirometry results) were extracted from medical charts. Multiple linear regression was used to determine the relationship between FPI-SF and FEV1 % predicted, and FPI-SF and COPD assessment test (CAT) score. Results: Overall, 1,775 patients participated (classified as GOLD 2017 group A, 14.8%; B, 46.6%; C, 2.6%; D, 36.0%). Physical activity impairment affected patients across all treatment regimens and GOLD groups (mean FPI-SF total score: 2.1), with the greatest impairment within FPI-SF observed for domains requiring most physical exertion, "physical exercise" and "maintaining the household" (mean FPI-SF scores: 1.7 and 1.8, respectively). Patients receiving loose triple therapy and those in GOLD group D had the highest impairment (mean FPI-SF total scores: both 1.9), and the lowest FEV1 % predicted (55.5% and 54.7%, respectively). FPI-SF total score correlated with FEV1 % predicted and more strongly with CAT score (all P<0.05). Conclusion: The stronger correlation between FPI-SF and CAT scores compared to FPI-SF and FEV1 % predicted suggests that symptoms may have a greater impact on patients' functional performance than lung function. Further longitudinal studies are required to establish a correlation between the effect of treatment on symptoms, lung function, and physical activity.