title: Identifying accelerometer nonwear and wear time in older adults.
abstract: BACKGROUND
  Five accelerometer-derived methods of identifying nonwear and wear time were compared with a self-report criterion in adults ≥ 56 years of age.
  
  
  METHODS
  Two hundred participants who reported wearing an Actical™ activity monitor for four to seven consecutive days and provided complete daily log sheet data (i.e., the criterion) were included. Four variables were obtained from log sheets: 1) dates the device was worn; 2) time(s) the participant put the device on each day; 3) time(s) the participant removed the device each day; and 4) duration of self-reported nonwear each day. Estimates of wear and nonwear time using 60, 90, 120, 150 and 180 minutes of consecutive zeroes were compared to estimates derived from log sheets.
  
  
  RESULTS
  Compared with the log sheet, mean daily wear time varied from -84, -43, -24, -14 and -8 min/day for the 60-min, 90-min, 120-min, 150-min and 180-min algorithms, respectively. Daily log sheets indicated 8.5 nonwear bouts per week with 120-min, 150-min and 180-min algorithms estimating 8.2-8.9 nonwear bouts per week. The 60-min and 90-min methods substantially overestimated number of nonwear bouts per week and underestimated time spent in sedentary behavior. Sensitivity (number of compliant days correctly identified as compliant) improved with increasing minutes of consecutive zero counts and stabilized at the 120-min algorithm. The proportion of wear time being sedentary and absolute and proportion of time spent in physical activity of varying intensities were nearly identical for each method.
  
  
  CONCLUSIONS
  Utilization of at least 120 minutes of consecutive zero counts will provide dependable population-based estimates of wear and nonwear time, and time spent being sedentary and active in older adults wearing the Actical™ activity monitor.
authors.forename: Brent
authors.initials: B
authors.lastname: Hutto
authors.forename: Virginia J
authors.initials: VJ
authors.lastname: Howard
authors.forename: Steven N
authors.initials: SN
authors.lastname: Blair
authors.forename: Natalie
authors.initials: N
authors.lastname: Colabianchi
authors.forename: John E
authors.initials: JE
authors.lastname: Vena
authors.forename: David
authors.initials: D
authors.lastname: Rhodes
authors.affiliation: Exercise and Wellness Program, School of Nutrition and Health Promotion, Arizona State University, 500 North Third Street, MC 3020, Phoenix, AZ 85004, USA. Steven.Hooker@asu.edu.
authors.forename: Steven P
authors.initials: SP
authors.lastname: Hooker
mesh_terms: D061725:Accelerometry / Q000295:instrumentation* / Q000379:methods*; D001741:Black or African American; D000368:Aged; D015992:Body Mass Index; D005260:Female; D015438:Health Behavior; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D050177:Overweight / Q000378:metabolism; D010349:Patient Compliance / Q000706:statistics & numerical data*; D011446:Prospective Studies; D057185:Sedentary Behavior; D057566:Self Report; D044465:White People