Development of disability in chronic obstructive pulmonary disease : beyond lung function MarkDEisner, CarlosIribarren, PaulDBlanc, EdwardHYelin, LynnAckerson, NancyByl, TheodoreAOmachi, StephenSidney, PatriciaPKatz Thorax : originally published online November 3, 2010 Department of Pulmonology R3 구자원

 COPD & Disability 10-fold higher risk Associated with diabetes or heart disease Reduce ability to perform basic self-care tasks Structural or functional alteration of organ system  functional limitation  disability  Hypothesis For a given level of respiratory impairment, the development of specific non-respiratory impairments and functional limitations will determine the risk of disability in COPD Background

 Recruitment and follow-up of the cohort The Function, Living, Outcomes and Work (FLOW) study of COPD Recruited a population-based cohort of 1202 Kaiser Permanente Medical Care Program (KPMCP) members - recently treated for COPD. A diagnosis of COPD was confirmed, using Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria. conducted structured telephone interviews 1202 subjects interviewed at baseline, 40 subjects subsequently died completed interview follow-up in 1051 subjects, 87% completion rate Methods

 Respiratory impairment Spirometry according to American Thoracic Society (ATS) Guidelines. Baseline oxygen saturation  Non-respiratory impairment assessment: body composition and muscle strength lean-to-fat ratio as a key measure of body composition. Isometric skeletal muscle strength, hand-held dynamometer, Knee extensor (quadriceps), hip extensor and hip abductor (ie, gluteus medius) strength, In the upper extremity, power grip, precision grip and elbow flexion strength  Functional limitations Assessment(decreased capacity or capability) Lower extremity function : Short Physical Performance Battery (SPPB) - tests of standing balance, gait speed and chair stand Balance : the functional reach test A summary performance score (0~12)- three performance measures The Six Minute Walk Test - Submaximal exercise performance British Medical Research Council (MRC) dyspnea scale : Mobility- related dyspnea Mini-Mental State Examination - Cognitive function

 Study outcome: measurement of COPD-related disability Valued Life Activities scale Primary measure of prospective disability - a dichotomous study outcome as a score increase of at least 3.3% from baseline. Secondary disability outcome - the development of any new activity domain that cannot be performed due to COPD  Statistical analysis Bivariate analysis - t-test (p<0.05) Multivariable logistic regression analysis – evaluate the impact of respiratory impairment, impact of each non-respiratory impairment and functional limitation The c-statistic - to quantify the area under the receiver operating characteristic (ROC) curve Delong and colleagues - statistically compare the area under each ROC curve

Results

FEV1/FVC ratio <0.70 and FEV1 < 80% predicted

 Prospective development of disability was a common occurrence in younger adults with COPD  Non-respiratory impairment and Functional limitations in body systems had a greater impact on disablement  Require a paradigm shift in COPD: the assessment and treatment of airway obstruction will not be sufficient to prevent the development of COPD-related disability.  Limitation Some possibility of misclassification of COPD Selection bias (ex: socioeconomic status) Intentionally recruited younger subjects Persons who are not receiving treatment for COPD. Discussion

 Development of non-respiratory impairment and functional limitations appear to be critical determinants of disablement.  Prevention and treatment of disability require a comprehensive approach to the COPD patient. Conclusion