title: Sedentary behavior and physical function: objective evidence from the Osteoarthritis Initiative.
abstract: OBJECTIVE
  Investigate the relationship between sedentary behavior and physical function in adults with knee osteoarthritis (OA), controlling for moderate-vigorous physical activity (MVPA) levels.
  
  
  METHODS
  Sedentary behavior was objectively measured by accelerometer on 1,168 participants ages 49-83 years in the Osteoarthritis Initiative with radiographic knee OA at the 48-month clinic visit. Physical function was assessed using 20-meter walk and chair stand testing. Sedentary behavior was identified by accelerometer activity counts/minute <100. The cross-sectional association between sedentary quartiles and physical function was examined by multiple linear regression, adjusting for demographic factors (age, sex, race/ethnicity, education level), health factors (comorbidity, body mass index, knee pain, knee OA severity, presence of knee symptoms), and average daily MVPA minutes.
  
  
  RESULTS
  Adults with knee OA spent two-thirds of their daily time in sedentary behavior. The average gait speed among the most sedentary quartile was 3.88 feet/second, which was significantly slower than the speed of the less sedentary groups (4.23, 4.33, and 4.33 feet/second, respectively). The average chair stand rate among the most sedentary group was significantly lower (25.9 stands/minute) than the rates of the less sedentary behavior groups (28.9, 29.1, and 31.1 stands/minute, respectively). These trends remained significant in multivariable analyses adjusted for demographic factors, health factors, and average daily MVPA minutes.
  
  
  CONCLUSIONS
  Being less sedentary was related to better physical function in adults with knee OA independent of MVPA time. These findings support guidelines to encourage adults with knee OA to decrease time spent in sedentary behavior in order to improve physical function.
authors.affiliation: Northwestern University, Chicago, Illinois.
authors.forename: Jungwha
authors.initials: J
authors.lastname: Lee
authors.forename: Rowland W
authors.initials: RW
authors.lastname: Chang
authors.forename: Linda
authors.initials: L
authors.lastname: Ehrlich-Jones
authors.forename: C Kent
authors.initials: CK
authors.lastname: Kwoh
authors.forename: Michael
authors.initials: M
authors.lastname: Nevitt
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Semanik
authors.forename: Leena
authors.initials: L
authors.lastname: Sharma
authors.forename: Min-Woong
authors.initials: MW
authors.lastname: Sohn
authors.forename: Jing
authors.initials: J
authors.lastname: Song
authors.forename: Dorothy D
authors.initials: DD
authors.lastname: Dunlop
mesh_terms: D056044:Actigraphy; D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D018771:Arthralgia / Q000503:physiopathology / Q000523:psychology; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D005080:Exercise Test; D005260:Female; D005684:Gait; D006304:Health Status; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D015999:Multivariate Analysis; D020370:Osteoarthritis, Knee / Q000175:diagnosis / Q000503:physiopathology* / Q000523:psychology*; D010147:Pain Measurement; D011237:Predictive Value of Tests; D011859:Radiography; D012307:Risk Factors; D057185:Sedentary Behavior; D013997:Time Factors; D014481:United States; D016138:Walking