title: Prognostic value of the objective measurement of daily physical activity in patients with COPD.
abstract: BACKGROUND
  Subjective measurement of physical activity using questionnaires has prognostic value in COPD. However, their lack of accuracy and large individual variability limit their use for evaluation on an individual basis. We evaluated the capacity of the objective measurement of daily physical activity in patients with COPD using accelerometers to estimate their prognostic value.
  
  
  METHODS
  In 173 consecutive subjects with moderate to very severe COPD, daily physical activity was measured using a triaxial accelerometer providing a mean of 1-min movement epochs as vector magnitude units (VMUs). Patients were evaluated by lung function testing and 6-min walk, incremental exercise, and constant work rate tests. Patients were followed for 5 to 8 years, and the end points were all-cause mortality, hospitalization for COPD exacerbation, and annual declining FEV(1).
  
  
  RESULTS
  After adjusting for relevant confounders, a high VMU decreased the mortality risk (adjusted hazard ratio [HR], 0.986; 95% CI, 0.981-0.992), and in a multivariate model, comorbidity, endurance time, and VMU were retained as independent predictors of mortality. The time until first admission due to COPD exacerbation was shorter for the patients with lower levels of VMU (adjusted HR, 0.989; 95% CI, 0.983-0.995). Moreover, patients with higher VMU had a lower hospitalization risk than those with a low VMU (adjusted incidence rate ratio, 0.099; 95% CI, 0.033-0.293). In contrast, VMU was not identified as an independent predictor of the annual FEV(1) decline.
  
  
  CONCLUSIONS
  The objective measurement of the daily physical activity in patients with COPD using an accelerometer constitutes an independent prognostic factor for mortality and hospitalization due to severe exacerbation.
authors.affiliation: Servicio de Neumología, Hospital Universitario La Paz, IdiPAZ, Spain; CIBER de Enfermedades Respiratorias (CIBERES), Palma de Mallorca, Spain. Electronic address: fgr01m@gmail.com.
authors.forename: Francisco
authors.initials: F
authors.lastname: Garcia-Rio
authors.affiliation: Sección de Neumología, Hospital Infanta Sofía, San Sebastián de los Reyes, Spain.
authors.forename: Blas
authors.initials: B
authors.lastname: Rojo
authors.affiliation: Servicio de Neumología, Hospital Universitario La Paz, IdiPAZ, Spain.
authors.forename: Raquel
authors.initials: R
authors.lastname: Casitas
authors.affiliation: Sección de Neumología, Hospital Infanta Leonor, Madrid, Spain.
authors.forename: Vanesa
authors.initials: V
authors.lastname: Lores
authors.affiliation: Sección de Bioestadística, Hospital Universitario La Paz, IdiPAZ, Spain.
authors.forename: Rosario
authors.initials: R
authors.lastname: Madero
authors.affiliation: Servicio de Neumología, Hospital Universitario La Paz, IdiPAZ, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Romero
authors.affiliation: Servicio de Neumología, Hospital Universitario La Paz, IdiPAZ, Spain.
authors.forename: Raúl
authors.initials: R
authors.lastname: Galera
authors.affiliation: Servicio de Neumología, Hospital Universitario La Paz, IdiPAZ, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Villasante
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D015331:Cohort Studies; D005260:Female; D006760:Hospitalization; D006801:Humans; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000295:instrumentation*; D009043:Motor Activity / Q000502:physiology*; D011237:Predictive Value of Tests; D011379:Prognosis; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology*; D012129:Respiratory Function Tests