title: Longitudinal study of the associations between change in sedentary behavior and change in adiposity during childhood and adolescence: Gateshead Millennium Study.
abstract: Sedentary time (ST) has been reported to have a range of negative health effects in adults, however, the evidence for such effects among children and adolescents is sparse. The primary aim of the study was to examine associations between changes in sedentary behavior (time and fragmentation) and changes in adiposity across childhood and adolescence.
  
  
  
  Participants were recruited as part of the Gateshead Millennium Study. Measures were taken at age 7 (n=502), 9 (n=506), 12 (n=420) and 15 years (n=306). Participants wore an ActiGraph GT1M and accelerometer epochs were 'sedentary' when recorded counts were ⩽25 counts per 15 s. ST was calculated and fragmentation (SF) was assessed by calculating the number of sedentary bouts per sedentary hour. Associations of changes in ST and SF with changes in adiposity (body mass index (BMI), and fat mass index (FMI)) were examined using bivariate linear spline models.
  
  
  
  Increasing ST by 1% per year was associated with an increase in BMI of 0.08 kg m-2per year (95% CI: 0.06-0.10; P<0.001) and FMI of 0.15  kg m-2per year (0.11-0.19; P<0.001). Change in SF was associated with BMI and FMI (P<0.001). An increase of 1 bout per sedentary hour per year (that is, sedentary time becoming more fragmented) was associated with an increase in BMI of 0.07  kg m-2per year (0.06-0.09; P<0.001) and an increase in FMI of 0.14  kg m-2per year (0.10-0.18; P<0.001) over the 8 years period. However, an increase in SF between 9-12 years was associated with a 0.09  kg m-2per year decrease in BMI (-0.18-0.00; P=0.046) and 0.11  kg m-2per year decrease in FMI (-0.22-0.00; P=0.049).
  
  
  
  Increased ST and increased SF from 7-15 years were associated with increased adiposity. This is the first study to show age-specific associations between change in objectively measured sedentary behavior and adiposity after adjustment of moderate-to-vigorous-intensity physical activity in children and adolescents. The study suggests that, targeting sedentary behavior for obesity prevention may be most effective during periods in which we see large increases in ST.
authors.affiliation: Newcastle University, Institute of Health and Society, Newcastle upon Tyne, UK.
authors.forename: K D
authors.initials: KD
authors.lastname: Mann
authors.affiliation: University of Bristol, School of Social and Community Medicine, MRC integrative Epidemiology Unit at Bristol University, Bristol, UK.
authors.forename: L D
authors.initials: LD
authors.lastname: Howe
authors.affiliation: Newcastle University, Institute of Health and Society, Newcastle upon Tyne, UK.|Newcastle University, Human Nutrition Research Centre, Newcastle upon Tyne, UK.
authors.forename: L
authors.initials: L
authors.lastname: Basterfield
authors.affiliation: Newcastle University, Institute of Health and Society, Newcastle upon Tyne, UK.|Newcastle University, Human Nutrition Research Centre, Newcastle upon Tyne, UK.
authors.forename: K N
authors.initials: KN
authors.lastname: Parkinson
authors.affiliation: Newcastle University, Institute of Health and Society, Newcastle upon Tyne, UK.
authors.forename: M S
authors.initials: MS
authors.lastname: Pearce
authors.affiliation: Newcastle University, Institute of Health and Society, Newcastle upon Tyne, UK.|Newcastle University, Human Nutrition Research Centre, Newcastle upon Tyne, UK.
authors.forename: J K
authors.initials: JK
authors.lastname: Reilly
authors.affiliation: Newcastle University, Institute of Health and Society, Newcastle upon Tyne, UK.|Newcastle University, Human Nutrition Research Centre, Newcastle upon Tyne, UK.
authors.forename: A J
authors.initials: AJ
authors.lastname: Adamson
authors.affiliation: University of Strathclyde, School of Psychological Science and Health, Glasgow, Scotland.
authors.forename: J J
authors.initials: JJ
authors.lastname: Reilly
authors.affiliation: University of Strathclyde, School of Psychological Science and Health, Glasgow, Scotland.
authors.forename: X
authors.initials: X
authors.lastname: Janssen
mesh_terms: D061725:Accelerometry / Q000706:statistics & numerical data; D050154:Adiposity; D000293:Adolescent; D000294:Adolescent Behavior; D000367:Age Factors; D015992:Body Mass Index; D002648:Child; D002652:Child Behavior; D015444:Exercise / Q000502:physiology*; D005260:Female; D015438:Health Behavior; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D063766:Pediatric Obesity / Q000517:prevention & control; D040242:Risk Reduction Behavior; D057185:Sedentary Behavior; D006113:United Kingdom; D014505:Urban Population