title: Sedentary Behavior Is an Independent Predictor of Mortality in Subjects With COPD.
abstract: BACKGROUND
  The terms sedentary behavior and physical inactivity have been confusingly mixed. Although the association between physical inactivity and mortality has been shown previously in subjects with COPD, this association had not yet been investigated with regard to sedentarism. The aim of this work was to investigate the impact of sedentary behavior on mortality of subjects with COPD and to propose a cutoff point of sedentarism with prognostic value.
  
  
  METHODS
  In this retrospective cohort study, sedentary behavior was assessed with 2 activity monitors (DynaPort and Sensewear armband) in 101 subjects with COPD from 2006 to 2011. Vital status was then ascertained in 2015. The following 6 variables of sedentary behavior were analyzed: average of metabolic equivalent of task (MET)/d (reflecting intensity); time spent/d lying, sitting, and lying + sitting (reflecting duration of sedentary postures); and time spent/d in activities requiring <1.5 MET and <2 MET (reflecting intensity and duration of sedentary time). Cutoff points for sedentarism and their respective prognostic values were investigated for each variable.
  
  
  RESULTS
  Forty-one subjects (41%) died over a median (interquartile range) follow-up period of 62 (43-88) months. After adjusting for potential confounders in the Cox regression model, cutoff points from variables that combine duration of sedentary time and intensity <1.5 MET or <2 MET were associated with the increased risk of mortality. The strongest independent cutoff for predicting mortality was ≥8.5 h/d spent in sedentary activities <1.5 MET (area under the curve 0.76; hazard ratio 4.09, 95% CI 1.90-8.78;P< .001).
  
  
  CONCLUSIONS
  Sedentary behavior was an independent predictor of mortality in subjects with COPD, even adjusting for moderate-to-vigorous physical activity and a number of other variables. Mortality was higher in subjects with COPD who spend ≥8.5 h/d in activities requiring <1.5 MET. These findings may open room for future studies aiming at decreasing sedentary time as a promising strategy to reduce mortality risk in subjects with COPD.
authors.affiliation: Laboratory of Research in Respiratory Physiotherapy (LFIP), Department of Physiotherapy.
authors.forename: Karina C
authors.initials: KC
authors.lastname: Furlanetto
authors.affiliation: Laboratory of Research in Respiratory Physiotherapy (LFIP), Department of Physiotherapy.
authors.forename: Leila
authors.initials: L
authors.lastname: Donária
authors.affiliation: Laboratory of Research in Respiratory Physiotherapy (LFIP), Department of Physiotherapy.
authors.forename: Lorena P
authors.initials: LP
authors.lastname: Schneider
authors.affiliation: Laboratory of Research in Respiratory Physiotherapy (LFIP), Department of Physiotherapy.
authors.forename: José R
authors.initials: JR
authors.lastname: Lopes
authors.affiliation: Laboratory of Research in Respiratory Physiotherapy (LFIP), Department of Physiotherapy.|Department of Medicine, Universidade Estadual de Londrina (UEL), Londrina, Brazil.
authors.forename: Marcos
authors.initials: M
authors.lastname: Ribeiro
authors.affiliation: Biological and Health Sciences Research Center, Universidade Norte do Paraná (UNOPAR), Londrina, Paraná, Brazil.
authors.forename: Karen Bp
authors.initials: KB
authors.lastname: Fernandes
authors.affiliation: Laboratory of Research in Respiratory Physiotherapy (LFIP), Department of Physiotherapy.
authors.forename: Nidia A
authors.initials: NA
authors.lastname: Hernandes
authors.affiliation: Laboratory of Research in Respiratory Physiotherapy (LFIP), Department of Physiotherapy fabiopitta@uol.com.br.
authors.forename: Fabio
authors.initials: F
authors.lastname: Pitta
mesh_terms: D000368:Aged; D015444:Exercise / Q000502:physiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D016016:Proportional Hazards Models; D029424:Pulmonary Disease, Chronic Obstructive / Q000401:mortality* / Q000503:physiopathology; D012189:Retrospective Studies; D012307:Risk Factors; D057185:Sedentary Behavior; D013997:Time Factors
keywords: chronic obstructive pulmonary disease; longitudinal studies; mortality; physical activity; sedentary lifestyle; survival analysis