title: Sedentary Behavior as a Risk Factor for Physical Frailty Independent of Moderate Activity: Results From the Osteoarthritis Initiative.
abstract: OBJECTIVE
  This prospective longitudinal study investigated the association between baseline objectively measured sedentary time and 2-year onset of physical frailty.
  
  
  METHODS
  We studied 1333 Osteoarthritis Initiative participants 55 to 83 years of age who were at risk for physical frailty, as assessed via low gait speed (< 0.6 m per second) or inability to perform a single chair stand. Baseline sedentary time was assessed through accelerometer monitoring. Hazard ratios (HRs) for physical frailty onset were estimated with discrete survival methods that controlled for moderate physical activity, sociodemographic characteristics, baseline gait and chair stand functioning, and health factors.
  
  
  RESULTS
  The incidence of physical frailty in this high-risk group was 20.7 per 1000 person-years. Greater baseline sedentary time (adjusted HR = 1.36 per sedentary hour; 95% confidence interval [CI] = 1.02, 1.79) was significantly related to incident physical frailty after control for time spent in moderate-intensity activities and other covariates.
  
  
  CONCLUSIONS
  Our prospective data demonstrated a strong relationship between daily sedentary time and development of physical frailty distinct from insufficient moderate activity. Interventions that promote reductions in sedentary behaviors in addition to increases in physical activity may help decrease physical frailty onset.
authors.affiliation: Jing Song, Lee A. Lindquist, Rowland W. Chang, Jungwha Lee, and Dorothy D. Dunlop are with the Northwestern University Feinberg School of Medicine, Chicago, IL. Pamela A. Semanik is with the Rush University School of Medicine, Chicago. Linda S. Ehrlich-Jones is with the Center for Rehabilitation Outcome Research, Rehabilitation Institute of Chicago. Min-Woong Sohn is with the University of Virginia School of Medicine, Charlottesville.
authors.forename: Jing
authors.initials: J
authors.lastname: Song
authors.forename: Lee A
authors.initials: LA
authors.lastname: Lindquist
authors.forename: Rowland W
authors.initials: RW
authors.lastname: Chang
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Semanik
authors.forename: Linda S
authors.initials: LS
authors.lastname: Ehrlich-Jones
authors.forename: Jungwha
authors.initials: J
authors.lastname: Lee
authors.forename: Min-Woong
authors.initials: MW
authors.lastname: Sohn
authors.forename: Dorothy D
authors.initials: DD
authors.lastname: Dunlop
mesh_terms: D061725:Accelerometry; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D016330:Frail Elderly / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D010003:Osteoarthritis / Q000453:epidemiology; D011446:Prospective Studies; D012307:Risk Factors; D057185:Sedentary Behavior