title: Separating bedtime rest from activity using waist or wrist-worn accelerometers in youth.
abstract: Recent interest in sedentary behavior and technological advances expanded use of watch-size accelerometers for continuous monitoring of physical activity (PA) over extended periods (e.g., 24 h/day for 1 week) in studies conducted in natural living environment. This approach necessitates the development of new methods separating bedtime rest and activity periods from the accelerometer recordings. The goal of this study was to develop a decision tree with acceptable accuracy for separating bedtime rest from activity in youth using accelerometer placed on waist or wrist. Minute-by-minute accelerometry data were collected from 81 youth (10-18 years old, 47 females) during a monitored 24-h stay in a whole-room indirect calorimeter equipped with a force platform covering the floor to detect movement. Receiver Operating Characteristic (ROC) curve analysis was used to determine the accelerometer cut points for rest and activity. To examine the classification differences, the accelerometer bedtime rest and activity classified by the algorithm in the development group (n = 41) were compared with actual bedtime rest and activity classification obtained from the room calorimeter-measured metabolic rate and movement data. The selected optimal bedtime rest cut points were 20 and 250 counts/min for the waist- and the wrist-worn accelerometer, respectively. The selected optimal activity cut points were 500 and 3,000 counts/min for waist and wrist-worn accelerometers, respectively. Bedtime rest and activity were correctly classified by the algorithm in the validation group (n = 40) by both waist- (sensitivity: 0.983, specificity: 0.946, area under ROC curve: 0. 872) and wrist-worn (0.999, 0.980 and 0.943) accelerometers. The decision tree classified bedtime rest correctly with higher accuracy than commonly used automated algorithm for both waist- and wrist-warn accelerometer (all p<0.001). We concluded that cut points developed and validated for waist- and wrist-worn uniaxial accelerometer have a good power for accurate separation of time spent in bedtime rest from activity in youth.
authors.affiliation: Energy Balance Laboratory, Division of Gastroenterology, Hepatology and Nutrition, Department of Medicine, Vanderbilt University, Nashville, Tennessee, United States of America.
authors.forename: Dustin J
authors.initials: DJ
authors.lastname: Tracy
authors.affiliation: Energy Balance Laboratory, Division of Gastroenterology, Hepatology and Nutrition, Department of Medicine, Vanderbilt University, Nashville, Tennessee, United States of America.
authors.forename: Zhiyi
authors.initials: Z
authors.lastname: Xu
authors.affiliation: Department of Biostatistics, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America.
authors.forename: Leena
authors.initials: L
authors.lastname: Choi
authors.affiliation: Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America.
authors.forename: Sari
authors.initials: S
authors.lastname: Acra
authors.affiliation: National Institute of Diabetes and Digestive and Kidney Disease, Diabetes, Endocrinology, and Obesity Branch, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Kong Y
authors.initials: KY
authors.lastname: Chen
authors.affiliation: Energy Balance Laboratory, Division of Gastroenterology, Hepatology and Nutrition, Department of Medicine, Vanderbilt University, Nashville, Tennessee, United States of America.
authors.forename: Maciej S
authors.initials: MS
authors.lastname: Buchowski
mesh_terms: D061725:Accelerometry / Q000295:instrumentation*; D000293:Adolescent; D002153:Calorimetry, Indirect / Q000295:instrumentation*; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D018670:Monitoring, Ambulatory / Q000295:instrumentation*; D009043:Motor Activity / Q000502:physiology*; D012146:Rest / Q000502:physiology*
references.citation: PLoS One. 2012;7(10):e48089
references.pmid: 23110178
references.citation: Med Sci Sports Exerc. 2008 Jan;40(1):181-8
references.pmid: 18091006
references.citation: Med Sci Sports Exerc. 2012 Oct;44(10):2009-16
references.pmid: 22525772
references.citation: Curr Opin Psychiatry. 2012 Sep;25(5):391-7
references.pmid: 22801357
references.citation: J Physiol. 1949 Aug;109(1-2):1-9
references.pmid: 15394301
references.citation: Obesity (Silver Spring). 2009 Aug;17(8):1596-602
references.pmid: 19247272
references.citation: Pediatr Exerc Sci. 2007 Aug;19(3):252-66
references.pmid: 18019585
references.citation: Eur J Clin Nutr. 2004 May;58(5):828-37
references.pmid: 15116087
references.citation: J Biomech. 1993 Mar;26(3):229-41
references.pmid: 8468336
references.citation: Res Q Exerc Sport. 2009 Sep;80(3):445-53
references.pmid: 19791630
references.citation: Am J Prev Med. 2012 May;42(5):445-51
references.pmid: 22516483
references.citation: IEEE Trans Biomed Eng. 2011 Apr;58(4):920-6
references.pmid: 21172750
references.citation: Med Sci Sports Exerc. 2012 Jan;44(1 Suppl 1):S32-8
references.pmid: 22157772
references.citation: Am J Prev Med. 2011 Aug;41(2):178-88
references.pmid: 21767726
references.citation: Appl Physiol Nutr Metab. 2014 Jan;39(1):53-7
references.pmid: 24383507
references.citation: J Pediatr Nurs. 2012 Apr;27(2):127-33
references.pmid: 22341191
references.citation: Am J Prev Med. 2009 Jul;37(1 Suppl):S40-9
references.pmid: 19524155
references.citation: Semin Nucl Med. 1978 Oct;8(4):283-98
references.pmid: 112681
references.citation: Med Sci Sports Exerc. 2005 Nov;37(11 Suppl):S531-43
references.pmid: 16294116
references.citation: J Pediatr. 2005 Jun;146(6):732-7
references.pmid: 15973308
references.citation: J Appl Physiol (1985). 1994 Jun;76(6):2686-91
references.pmid: 7928901
references.citation: Med Sci Sports Exerc. 2011 Jul;43(7):1360-8
references.pmid: 21131873
references.citation: Med Sci Sports Exerc. 2005 Nov;37(11 Suppl):S490-500
references.pmid: 16294112
references.citation: Sleep Med Rev. 2011 Aug;15(4):259-67
references.pmid: 21237680
references.citation: Am J Prev Med. 2011 Dec;41(6):596-602
references.pmid: 22099236
references.citation: Sleep. 1994 Apr;17(3):201-7
references.pmid: 7939118
references.citation: J Epidemiol. 2012;22(5):462-8
references.pmid: 22850546
references.citation: Med Sci Sports Exerc. 2011 Feb;43(2):357-64
references.pmid: 20581716
references.citation: Med Sci Sports Exerc. 2009 Apr;41(4):818-27
references.pmid: 19276851
references.citation: J Appl Physiol (1985). 2010 Feb;108(2):314-27
references.pmid: 19959770
references.citation: Med Sci Sports Exerc. 2004 Jul;36(7):1259-66
references.pmid: 15235335
references.citation: Med Sci Sports Exerc. 2012 Jan;44(1 Suppl 1):S1-4
references.pmid: 22157769
references.citation: PLoS One. 2012;7(6):e37975
references.pmid: 22745660