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Table 1 Characteristics of participants by sex, Bt20+

From: Adolescent physical activity, sedentary behavior and sleep in relation to body composition at age 18 years in urban South Africa, Birth-to-Twenty+ Cohort

  Males Females
N 638 699
Childhood characteristics
 Birth order, %
  First born 38 41
 BMIZ at age 7/8 or 9 ya 0.0 (0.9) 0.0 (1.0)
Maternal characteristics
 Schooling at child age 7/8 y, %   
  Matriculated 29 31
Household characteristics
 SES asset quintile at child age 7/8 y, %
  1 (lowest) 16 22
  2 21 17
  3 30 29
  4 23 19
  5 (highest) 10 13
Adolescent trajectories
informal activity, %
  Decreasing over time 93 95
  Increasing over time 7 5
Organized sports participation, %
  Males
   Consistently low 82  
   Decreasing from adequate to low 11  
   Increasing from low to adequate 7  
  Females
   No sports participation   89
   Some sports participation   11
Walking to and from school, %
  Consistently 150 min/week 83 75
  Consistently 300 min/week 17 25
Overall physical activity, %
  Decreasing activity over time and do not walk to school 22 31
  Decreasing activity over time but consistently walk to school 50 54
  Consistently more active and consistently walk to school 28 15
Sedentary behavior, %
  Males
   Consistently low 78  
   Consistently high 12  
   Increasing from low to high 10  
  Females
   Initially low but increasing   92
   Consistently high   8
Schoolnight sleep, %
   ≤ 8 h/night 35 65
   ≥ 9 h/night 65 35
Young-adult characteristics (18 y)
 Heighta, cm 170.7 (6.5) 159.6 (6.1)
 BMIa, kg/m2 20.3 (3.2) 23.2 (4.6)
 Waist-circumferencea, cm 72.0 (7.2) 75.6 (12.9)
 Fat mass indexa,b, kg/m2 2.5 (1.5) 7.3 (3.0)
 Lean mass indexa,b, kg/m2 15.0 (1.5) 13.1 (1.6)
 Body fata,b, % 13.2 (5.5) 33.6 (6.7)
  1. a Expressed as mean (standard deviation)
  2. b data collected from only 958 participants (449 males and 509 females)