title: Association of daily physical activity volume and intensity with COPD severity.
abstract: OBJECTIVE
  The purpose of this study was to assess whether daily walking activity is indicative of disease severity in patients with COPD.
  
  
  METHODS
  Daily activity was measured by accelerometry in 107 COPD: GOLD II (N=28), GOLD III (N=51), and GOLD IV (N=25). Steps per day and times (min/day) spent passively, actively, walking (WLK, 0-5 km/h), and fast walking (FWLK, >5 km/h) were analyzed. Total walking time (TWT) was computed.
  
  
  RESULTS
  Times spent WLK (P=0.031), FWLK (P=0.001), TWT (P=0.021), and steps per day (P=0.013) differed significantly between GOLD stages. There was a significant negative correlation between TWK and GOLD stage (R=-0.35; P<0.0001), BODE index (R=-0.58; P<0.0001), and MMRC dyspnea scale (R=-0.65; P<0.0001). Logistic regression analysis showed that both TWT and FWLK were independently and significantly associated with BODE index ≥ 6 (P=0.029 and P=0.040, respectively). The corresponding AUC-value with 95% CI for TWT was 0.80 (95% CI: 0.70 to 0.90) and 0.87 (95% CI: 0.81 to 0.94) for FWLK. The corresponding optimal cut-off value for TWT was 33.3 min/day (sensitivity: 86%; specificity 70%) and FWLK was 0.10 min/day (sensitivity: 93%; specificity 76%).
  
  
  CONCLUSIONS
  Daily walking activity, in particular walking intensity, is significant predictor of disease severity in patients with COPD. Objective measures of habitual activity might provide additive value in assessing the likelihood of poor prognosis in this patient cohort.
authors.affiliation: Department of Sports Medicine, Institute of Exercise and Health Sciences, University of Basel, Brüglingen 33, CH-4052 Basel, Switzerland. melissa.jehn@unibas.ch
authors.forename: Melissa
authors.initials: M
authors.lastname: Jehn
authors.forename: Arno
authors.initials: A
authors.lastname: Schmidt-Trucksäss
authors.forename: Anja
authors.initials: A
authors.lastname: Meyer
authors.forename: Christian
authors.initials: C
authors.lastname: Schindler
authors.forename: Michael
authors.initials: M
authors.lastname: Tamm
authors.forename: Daiana
authors.initials: D
authors.lastname: Stolz
mesh_terms: D015331:Cohort Studies; D004417:Dyspnea / Q000453:epidemiology / Q000503:physiopathology*; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology / Q000503:physiopathology*; D011788:Quality of Life; D012720:Severity of Illness Index; D016138:Walking