Body composition and functional limitation in COPD.
BACKGROUND
Low body mass index has been associated with increased mortality in severe COPD. The impact of body composition earlier in the disease remains unclear. We studied the impact of body composition on the risk of functional limitation in COPD.


METHODS
We used bioelectrical impedance to estimate body composition in a cohort of 355 younger adults with COPD who had a broad spectrum of severity.


RESULTS
Among women, a higher lean-to-fat ratio was associated with a lower risk of self-reported functional limitation after controlling for age, height, pulmonary function impairment, race, education, and smoking history (OR 0.45 per 0.50 increment in lean-to-fat ratio; 95% CI 0.28 to 0.74). Among men, a higher lean-to-fat ratio was associated with a greater distance walked in 6 minutes (mean difference 40 meters per 0.50 ratio increment; 95% CI 9 to 71 meters). In women, the lean-to-fat ratio was associated with an even greater distance walked (mean difference 162 meters per 0.50 increment; 95% CI 97 to 228 meters). In women, higher lean-to-fat ratio was also associated with better Short Physical Performance Battery Scores. In further analysis, the accumulation of greater fat mass, and not the loss of lean mass, was most strongly associated with functional limitation among both sexes.


CONCLUSIONS
Body composition is an important non-pulmonary impairment that modulates the risk of functional limitation in COPD, even after taking pulmonary function into account. Body composition abnormalities may represent an important area for screening and preventive intervention in COPD.
Eisner
Mark D
MD
Division of Occupational and Environmental Medicine, Department of Medicine, University of California, San Francisco, USA. mark.eisner@ucsf.edu
Blanc
Paul D
PD
Sidney
Steve
S
Yelin
Edward H
EH
Lathon
Phenius V
PV
Katz
Patricia P
PP
Tolstykh
Irina
I
Ackerson
Lynn
L
Iribarren
Carlos
C
D001823:Body Composition; D002140:California; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D008329:Managed Care Programs; D008875:Middle Aged; D016017:Odds Ratio; D004856:Postural Balance; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012119:Respiration; D012720:Severity of Illness Index; D013147:Spirometry; D016138:Walking