title: An index of daily step count and systemic inflammation predicts clinical outcomes in chronic obstructive pulmonary disease.
abstract: BACKGROUND
  Identification of persons with chronic obstructive pulmonary disease (COPD) at risk for acute exacerbations (AEs) targets them for close monitoring.
  
  
  OBJECTIVE
  We examined the ability of a novel index combining physical activity and systemic inflammation to identify persons at risk for AEs.
  
  
  METHODS
  In an observational cohort study of 167 persons with COPD, we assessed daily step count, a direct measure of physical activity, with the StepWatch Activity Monitor and measured plasma C-reactive protein (CRP) and IL-6 levels. AEs and COPD-related hospitalizations were assessed prospectively over a median of 16 months. Predictors of AEs and COPD-related hospitalizations were assessed using negative binomial models.
  
  
  RESULTS
  Median daily step count was 5,203 steps (interquartile range, 3,627-7,024). Subjects with daily step count ≤ 5,203 and CRP > 3 mg/l had an increased rate of AEs (rate ratio [RR], 2.06; 95% confidence interval [CI], 1.30-3.27) and COPD-related hospitalizations (RR, 3.51; 95% CI, 1.73-7.11) compared with subjects with daily step count > 5,203 and CRP ≤ 3 mg/l, adjusting for FEV1% predicted and prednisone use for AE in the previous year. Similarly, subjects with daily step count ≤ 5,203 and IL-6 > 2 pg/ml had an increased rate of AEs (RR, 2.04; 95% CI, 1.14-3.63) and COPD-related hospitalizations (RR, 4.27; 95% CI, 1.56-11.7) compared with subjects with daily step count > 5,203 and IL-6 ≤ 2 pg/ml.
  
  
  CONCLUSIONS
  An index combining daily step count and systemic inflammation can predict AEs and COPD-related hospitalizations. A validation study in a separate cohort is needed to confirm the utility of the proposed index as a clinical tool to risk stratify persons with COPD.
authors.affiliation: 1 Department of Veteran's Affairs, Veterans Health Administration, Rehabilitation Research and Development Service.
authors.forename: Marilyn L
authors.initials: ML
authors.lastname: Moy
authors.forename: Merilee
authors.initials: M
authors.lastname: Teylan
authors.forename: Valery A
authors.initials: VA
authors.lastname: Danilack
authors.forename: David R
authors.initials: DR
authors.lastname: Gagnon
authors.forename: Eric
authors.initials: E
authors.lastname: Garshick
mesh_terms: D061725:Accelerometry; D000368:Aged; D015415:Biomarkers; D002097:C-Reactive Protein / Q000276:immunology*; D015331:Cohort Studies; D018450:Disease Progression; D005260:Female; D005541:Forced Expiratory Volume; D006760:Hospitalization; D006801:Humans; D007249:Inflammation / Q000276:immunology; D015850:Interleukin-6 / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D011379:Prognosis; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000276:immunology / Q000503:physiopathology
chemical_list: D015415:Biomarkers; C508600:IL6 protein, human; D015850:Interleukin-6; D002097:C-Reactive Protein