title: Improving wear time compliance with a 24-hour waist-worn accelerometer protocol in the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE).
abstract: BACKGROUND
  We compared 24-hour waist-worn accelerometer wear time characteristics of 9-11 year old children in the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE) to similarly aged U.S. children providing waking-hours waist-worn accelerometer data in the 2003-2006 National Health and Nutrition Examination Survey (NHANES).
  
  
  METHODS
  Valid cases were defined as having ≥4 days with ≥10 hours of waking wear time in a 24-hour period, including one weekend day. Previously published algorithms for extracting total sleep episode time from 24-hour accelerometer data and for identifying wear time (in both the 24-hour and waking-hours protocols) were applied. The number of valid days obtained and a ratio (percent) of valid cases to the number of participants originally wearing an accelerometer were computed for both ISCOLE and NHANES. Given the two surveys' discrepant sampling designs, wear time (minutes/day, hours/day) from U.S. ISCOLE was compared to NHANES using a meta-analytic approach. Wear time for the 11 additional countries participating in ISCOLE were graphically compared with NHANES.
  
  
  RESULTS
  491 U.S. ISCOLE children (9.92±0.03 years of age [M±SE]) and 586 NHANES children (10.43 ± 0.04 years of age) were deemed valid cases. The ratio of valid cases to the number of participants originally wearing an accelerometer was 76.7% in U.S. ISCOLE and 62.6% in NHANES. Wear time averaged 1357.0 ± 4.2 minutes per 24-hour day in ISCOLE. Waking wear time was 884.4 ± 2.2 minutes/day for U.S. ISCOLE children and 822.6 ± 4.3 minutes/day in NHANES children (difference = 61.8 minutes/day, p < 0.001). Wear time characteristics were consistently higher in all ISCOLE study sites compared to the NHANES protocol.
  
  
  CONCLUSIONS
  A 24-hour waist-worn accelerometry protocol implemented in U.S. children produced 22.6 out of 24 hours of possible wear time, and 61.8 more minutes/day of waking wear time than a similarly implemented and processed waking wear time waist-worn accelerometry protocol. Consistent results were obtained internationally. The 24-hour protocol may produce an important increase in wear time compliance that also provides an opportunity to study the total sleep episode time separate and distinct from physical activity and sedentary time detected during waking-hours.
  
  
  BACKGROUND
  ClinicalTrials.gov NCT01722500 .
authors.affiliation: Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA, 70808, USA. tudor-locke@pbrc.edu.
authors.forename: Catrine
authors.initials: C
authors.lastname: Tudor-Locke
authors.affiliation: Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA, 70808, USA. tvbarrei@syr.edu.|Syracuse University, Syracuse, USA. tvbarrei@syr.edu.
authors.forename: Tiago V
authors.initials: TV
authors.lastname: Barreira
authors.affiliation: Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA, 70808, USA. john.schuna@oregonstate.edu.|Oregon State University, Corvallis, USA. john.schuna@oregonstate.edu.
authors.forename: John M
authors.initials: JM
authors.lastname: Schuna
authors.affiliation: Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA, 70808, USA. emily.mire@pbrc.edu.
authors.forename: Emily F
authors.initials: EF
authors.lastname: Mire
authors.affiliation: Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada. jpchaput@cheo.on.ca.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Chaput
authors.affiliation: University of Helsinki, Helsinki, Finland. mikael.fogelholm@helsinki.fi.
authors.forename: Mikael
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authors.lastname: Fogelholm
authors.affiliation: Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA, 70808, USA. gang.hu@pbrc.edu.
authors.forename: Gang
authors.initials: G
authors.lastname: Hu
authors.affiliation: St. Johns Research Institute, Bangalore, India. rebecca@sjri.res.in.
authors.forename: Rebecca
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authors.lastname: Kuriyan
authors.affiliation: St. Johns Research Institute, Bangalore, India. a.kurpad@sjri.res.in.
authors.forename: Anura
authors.initials: A
authors.lastname: Kurpad
authors.affiliation: University of Cape Town, Cape Town, South Africa. vicki.lambert@uct.ac.za.
authors.forename: Estelle V
authors.initials: EV
authors.lastname: Lambert
authors.affiliation: University of South Australia, Adelaide, Australia. carol.maher@unisa.edu.au.
authors.forename: Carol
authors.initials: C
authors.lastname: Maher
authors.affiliation: CIFI2D, Faculdade de Desporto, University of Porto, Porto, Portugal. jmaia@fade.up.pt.
authors.forename: José
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authors.lastname: Maia
authors.affiliation: Center of Studies of the Physical Fitness Research Laboratory from Sao Caetano do Sul (CELAFISCS), Sao Paulo, Brazil. matsudo@celafiscs.org.br.
authors.forename: Victor
authors.initials: V
authors.lastname: Matsudo
authors.affiliation: University of South Australia, Adelaide, Australia. timothy.olds@unisa.edu.au.
authors.forename: Tim
authors.initials: T
authors.lastname: Olds
authors.affiliation: Kenyatta University, Nairobi, Kenya. vonywera@gmail.com.
authors.forename: Vincent
authors.initials: V
authors.lastname: Onywera
authors.affiliation: School of Medicine, Universidad de los Andes, Bogota, Colombia. osarmien@uniandes.edu.co.
authors.forename: Olga L
authors.initials: OL
authors.lastname: Sarmiento
authors.affiliation: University of Bath, Bath, UK. m.standage@bath.ac.uk.
authors.forename: Martyn
authors.initials: M
authors.lastname: Standage
authors.affiliation: Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada. mtremblay@cheo.on.ca.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Tremblay
authors.affiliation: Tianjin Women's and Children's Health Center, Tianjin, China. juliapeizhao@qq.com.
authors.forename: Pei
authors.initials: P
authors.lastname: Zhao
authors.affiliation: Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA, 70808, USA. timothy.church@pbrc.edu.
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Church
authors.affiliation: Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA, 70808, USA. peter.katzmarzyk@pbrc.edu.
authors.forename: Peter T
authors.initials: PT
authors.lastname: Katzmarzyk
mesh_terms: D061725:Accelerometry / Q000379:methods*; D002648:Child; D002985:Clinical Protocols; D015444:Exercise; D005260:Female; D006801:Humans; D008019:Life Style; D008297:Male; D009043:Motor Activity; D009749:Nutrition Surveys; D063766:Pediatric Obesity / Q000209:etiology / Q000517:prevention & control; D012890:Sleep; D011795:Surveys and Questionnaires; D013997:Time Factors; D014481:United States; D014851:Wakefulness