American Journal of Epidemiology Advance Access originally published online on March 14, 2008
American Journal of Epidemiology 2008 167(9):1090-1101; doi:10.1093/aje/kwn025
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ORIGINAL CONTRIBUTIONS |
Pulmonary Function and the Risk of Functional Limitation in Chronic Obstructive Pulmonary Disease
1 Division of Occupational and Environmental Medicine and Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of California, San Francisco, CA
2 Division of Research, Kaiser Permanente, Oakland, CA
3 Institute for Health Policy Studies, Department of Medicine, University of California, San Francisco, CA
4 Department of Physical Therapy and Rehabilitation, University of California, San Francisco, CA
Correspondence to Dr. Mark D. Eisner, University of California, San Francisco, 350 Parnassus Avenue, Suite 609, San Francisco, CA 94117 (e-mail: mark.eisner{at}ucsf.edu).
Received for publication November 2, 2007. Accepted for publication January 23, 2008.
The authors' objective was to analyze the impact of respiratory impairment on the risk of physical functional limitations among adults with chronic obstructive pulmonary disease (COPD). They hypothesized that greater pulmonary function decrement would result in a broad array of physical functional limitations involving organ systems remote from the lung, a key step in the pathway leading to overall disability. The authors used baseline data from the Function, Living, Outcomes, and Work (FLOW) study, a prospective cohort study of adults with COPD recruited from northern California in 2005–2007. They studied the impact of pulmonary function impairment on the risk of functional limitations using validated measures: lower extremity function (Short Physical Performance Battery), submaximal exercise performance (6-Minute Walk Test), standing balance (Functional Reach Test), skeletal muscle strength (manual muscle testing with dynamometry), and self-reported functional limitation (standardized item battery). Multiple variable analysis was used to control for confounding by age, sex, race, height, educational attainment, and cigarette smoking. Greater pulmonary function impairment, as evidenced by lower forced expiratory volume in 1 second (FEV1), was associated with poorer Short Physical Performance Battery scores and less distance walked during the 6-Minute Walk Test. Lower forced expiratory volume in 1 second was also associated with weaker muscle strength and with a greater risk of self-reported functional limitation (p < 0.05). In conclusion, pulmonary function impairment is associated with multiple manifestations of physical functional limitation among COPD patients. Longitudinal follow-up can delineate the impact of these functional limitations on the prospective risk of disability, guiding preventive strategies that could attenuate the disablement process.
pulmonary disease; chronic obstructive
Abbreviations: CI, confidence interval; COPD, chronic obstructive pulmonary disease; FEV1, forced expiratory volume in 1 second; FLOW, Function, Living, Outcomes, and Work; GOLD, Global Initiative for Chronic Obstructive Lung Disease; KPMCP, Kaiser Permanente Medical Care Program; LOWESS, locally weighted regression scatterplot smoother