title: The impact of school-day variation in weight and height on National Child Measurement Programme body mass index-determined weight category in Year 6 children.
abstract: BACKGROUND
  In England, the National Child Measurement Programme (NCMP) annually measures the weight and height of Year 6 schoolchildren (age 10-11 years). While measurement protocols are defined, the time of measurement within the school day is not. This study examined the impact of school-day variation in weight and height on NCMP body mass index (BMI)-determined weight category in Year 6 children.
  
  
  METHODS
  Standing height and weight were measured in morning and afternoon sessions in 74 children, boys (n= 34; height: 141.16 ± 7.45 cm; weight: 36.48 ± 9.46 kg, BMI: 18.19 ± 3.98 kg/m(2) ) and girls (n= 40; height: 144.58 ± 7.66 cm; weight: 42.25 ± 11.29 kg; BMI: 19.97 ± 3.98 kg/m(2) ) aged 11 ± 0.3 years.
  
  
  RESULTS
  In the whole sample, height decreased (Mean =-0.51 cm, 95% CI: -0.39 to -0.64 cm, P= 0.01), weight did not change (Mdn = 36.40 to 36.35, P= 0.09) and BMI increased (Mdn = 18.04 to 18.13, P= 0.01). In girls weight increased (Mdn = 41.40 to 41.60, P= 0.01). BMI percentile increased (Mdn = 57th to 59.5th centile, P= 0.01). One girl increased in BMI category from morning to afternoon according to the clinical cut-offs (≤2nd, >91st and >98th) and three girls increased BMI category according to the population monitoring cut-offs (≤2nd, ≥85th, ≥95th).
  
  
  CONCLUSIONS
  School-day variation in height (and in girls alone, weight) impact upon increased BMI and BMI percentile in afternoon versus morning measurements in Year 6 children. Although not reaching statistical significance, resultant variation in categorization at the individual level may lead to unwarranted follow-up procedures being initiated. Further research with larger samples is required to further explore the impact of daily variability in height and weight upon both clinical and population monitoring BMI-determined weight status categorization in the NCMP.
authors.affiliation: Institute of Sport and Exercise Science, University of Worcester, Worcester, UK.
authors.forename: A C
authors.initials: AC
authors.lastname: Routen
authors.forename: M G
authors.initials: MG
authors.lastname: Edwards
authors.forename: D
authors.initials: D
authors.lastname: Upton
authors.forename: D M
authors.initials: DM
authors.lastname: Peters
mesh_terms: D000886:Anthropometry / Q000379:methods*; D001827:Body Height / Q000502:physiology; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology; D002648:Child; D002940:Circadian Rhythm; D004739:England; D005260:Female; D006801:Humans; D008297:Male; D009765:Obesity / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology; D015203:Reproducibility of Results; D012574:Schools