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Published on: August 25, 2017
Both pulmonary and extra-pulmonary factors predict the development of disability in chronic obstructive pulmonary
Jonathan P Singer1, Patricia P Katz, Carlos Iribarren
1Division of Pulmonary, Critical Care, Allergy and Sleep Medicine, Department of Medicine, University of California, San Francisco, CA 94143-0111, USA. jon.singer@ucsf.edu
Background:
Although chronic obstructive pulmonary disease (COPD) is a major cause of disability worldwide, its determinants remain poorly defined.
Objective:
We hypothesized that both pulmonary and extra-pulmonary factors would predict prospective disablement across a hierarchy of activities in persons with COPD.
Methods:
Six hundred and nine participants were studied at baseline (T0) and 2.5 years later (T1). The Valued Life Activities (VLA) scale quantified disability (10-point scale: 0 = no difficulty and 10 = unable to perform), defining disability as any activity newly rated 'unable to perform' at T1. Predictors included pulmonary (lung function, 6-minute walk distance and COPD severity score) and extra-pulmonary (quadriceps strength and lower extremity function) factors. Prospective disability risk was tested by separate logistic regression models for each predictor (baseline value and its change, T0-T1; odds ratios were scaled at 1 standard deviation per factor. Incident disability across a hierarchy of obligatory, committed and discretionary VLA subscales was compared.
Results:
Subjects manifested a 40% or greater increased odds of developing disability for each predictor (baseline and change over time). Disability in discretionary activities developed at a rate 2.2-times higher than observed in committed activities, which was in turn 2.5-times higher than the rate observed in obligatory activities (p < 0.05 for each level).
Conclusions:
Disability is common in COPD. Both pulmonary and extra-pulmonary factors are important in predicting its development.
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