title: A prospective study of decline in fat free mass and skeletal muscle strength in chronic obstructive pulmonary disease.
abstract: BACKGROUND
  Skeletal muscle depletion is an important complication of chronic obstructive pulmonary disease (COPD) but little prospective data exists about the rate at which it occurs and the factors that promote its development. We therefore prospectively investigated the impact of disease severity, exacerbation frequency and treatment with corticosteroids on change in body composition and maximum isometric quadriceps strength (QMVC) over one year.
  
  
  METHODS
  64 patients with stable COPD (FEV1 mean (SD) 35.8(18.4) %predicted) were recruited from clinic and studied on two occasions one year apart. Fat free mass was determined using bioelectrical impedance analysis and a disease specific regression equation.
  
  
  RESULTS
  QMVC fell from 34.8(1.5) kg to 33.3(1.5) kg (p = 0.04). The decline in quadriceps strength was greatest in those with the highest strength at baseline (R -0.28 p = 0.02) and was not correlated with lung function, exacerbation frequency or steroid treatment. Decline in fat free mass was similarly higher in those with largest FFM at baseline (R = -0.31 p = 0.01) but was more strongly correlated with greater gas trapping (R = -0.4 p = 0.001). Patients with frequent exacerbations (>1 per year) (n = 36) experienced a greater decline in fat free mass compared to infrequent exacerbators (n = 28) -1.3(3.7)kg vs. +1.2(3.1)kg (p = 0.005), as did patients on maintenance oral steroids (n = 8) -2.8(3.3) kg vs. +0.2(3.5) kg (p = 0.024) whereas in those who stopped smoking (n = 7) fat free mass increased; +2.7(3.1) kg vs. -0.51(3.5) kg (p = 0.026).
  
  
  CONCLUSIONS
  Decline in fat free mass in COPD is associated with worse lung function, continued cigarette consumption and frequent exacerbations. Factors predicting progression of quadriceps weakness could not be identified from the present cohort.
authors.affiliation: Respiratory Muscle Laboratory, Royal Brompton Hospital, Fulham Rd, London SW3 6NP, UK. n.hopkinson@ic.ac.uk
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Hopkinson
authors.forename: Rachel C
authors.initials: RC
authors.lastname: Tennant
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Dayer
authors.forename: Elisabeth B
authors.initials: EB
authors.lastname: Swallow
authors.forename: Trevor T
authors.initials: TT
authors.lastname: Hansel
authors.forename: John
authors.initials: J
authors.lastname: Moxham
authors.forename: Michael I
authors.initials: MI
authors.lastname: Polkey
mesh_terms: D000284:Administration, Oral; D000305:Adrenal Cortex Hormones / Q000008:administration & dosage; D000368:Aged; D001823:Body Composition / Q000187:drug effects; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000187:drug effects / Q000503:physiopathology*; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology*; D011788:Quality of Life; D012044:Regression Analysis; D012129:Respiratory Function Tests; D012132:Respiratory Muscles / Q000503:physiopathology; D016540:Smoking Cessation; D015431:Weight Loss / Q000187:drug effects
chemical_list: D000305:Adrenal Cortex Hormones