title: Improved reclassification of mortality risk by assessment of physical activity in patients referred for exercise testing.
abstract: BACKGROUND
  Inability to meet minimal guidelines on physical activity is associated with poor health outcomes, but quantifying activity can be complex. We studied whether a simple question regarding participation in regular activity improves risk classification for all-cause mortality.
  
  
  METHODS
  Maximal exercise testing was performed in 6962 patients (mean age, 58.9 ± 11 years) for clinical reasons. Subjects also were assessed for participation in regular activity using a simple yes/no response to meeting minimal recommendations on activity. The incremental value of adding a simple physical activity assessment to clinical, demographic, and exercise test information to predict mortality was determined using Cox proportional hazards models, net reclassification improvement, and integrated discrimination index during a mean follow-up of 9.7 ± 4 years.
  
  
  RESULTS
  Subjects who did not meet the minimal guidelines on activity had a lower exercise capacity (7.4 ± 4.3 vs 9.1 ± 3.6 metabolic equivalents, P < .0001) and a higher annual mortality rate (2.42% vs 1.71%, P < .001). Not meeting activity guidelines was associated with an age-adjusted 36% higher risk of mortality (hazard ratio, 1.36; 95% confidence interval, 1.22-1.51, P < .0001). Among clinical and exercise test variables, fitness had the highest C-index for predicting mortality (0.72, P < .001). The addition of physical activity classification to a model including traditional risk factors resulted in a net reclassification improvement of 22.8% (P < .001); adding fitness to the traditional risk factor model resulted in a net reclassification improvement of 43.5% (P < .001).
  
  
  CONCLUSIONS
  The addition of a simple assessment of physical activity status significantly improves reclassification of risk for all-cause mortality among patients who are referred for exercise testing.
authors.affiliation: Division of Cardiology, Veterans Affairs Palo Alto Health Care System, Palo Alto, Calif; Stanford University School of Medicine, Stanford, Calif. Electronic address: drj993@aol.com.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Myers
authors.affiliation: University of Pennsylvania, Philadelphia.
authors.forename: Kevin T
authors.initials: KT
authors.lastname: Nead
authors.affiliation: National University Heart Centre, Singapore.
authors.forename: Peter
authors.initials: P
authors.lastname: Chang
authors.affiliation: Division of Cardiology, Veterans Affairs Palo Alto Health Care System, Palo Alto, Calif.
authors.forename: Joshua
authors.initials: J
authors.lastname: Abella
authors.affiliation: Veterans Affairs Medical Center, Washington, DC.
authors.forename: Peter
authors.initials: P
authors.lastname: Kokkinos
authors.affiliation: Stanford University School of Medicine, Stanford, Calif; Division of Vascular Surgery, Stanford University, Stanford Cardiovascular Institute, Stanford, Calif.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Leeper
mesh_terms: D000328:Adult; D000368:Aged; D002317:Cardiovascular Agents / Q000627:therapeutic use; D002318:Cardiovascular Diseases / Q000175:diagnosis / Q000188:drug therapy / Q000401:mortality* / Q000503:physiopathology; D015897:Comorbidity; D015444:Exercise; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D008297:Male; D008487:Medical History Taking; D008875:Middle Aged; D009043:Motor Activity; D011237:Predictive Value of Tests; D018570:Risk Assessment; D012307:Risk Factors; D014728:Veterans
chemical_list: D002317:Cardiovascular Agents
keywords: Exercise capacity; Exercise testing; Mortality; Physical inactivity