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Table 1 Sample characteristics across age and gender groups in the national school-based survey

From: Short sleep duration is associated with specific food intake increase among school-aged children in China: a national cross-sectional study

  All (n = 62,517) 6–12 years old (n = 40,924) 13–18 years old (n = 20,593) P Value for age groups Boys (n = 32,257) Girls (n = 30,260) P Value for gender
Child characteristics, mean ± SD, median with quartile or %
 Female 48.4 47.3 50.5 < 0.001 0 100 < 0.001
 Age (years) 10.82(3.30) 8.98(1.88) 14.64(1.37) < 0.001 10.92(3.91) 11.06(3.22) < 0.001
 Height (cm) 145.82(17.09) 137.87(12.62) 163.50(8.41) < 0.001 148.25(18.10) 145.57(14.84) < 0.001
 Weight (kg) 40.94(15.53) 34.50(11.49) 55.78(12.79) < 0.001 43.71(17.17) 40.25(13.72) < 0.001
 BMI (kg2/m) 18.78(3.84) 17.71(3.42) 20.74(3.79) < 0.001 19.13(4.03) 18.42(3.59) < 0.001
Family income (%)     < 0.001    < 0.001
  < 5000 yuan/month 28.0 27.0 29.9   27.1 29.0  
  > 5000 yuan/month 14.2 15.2 12.3   14.0 14.4  
Not known 57.8 57.8 57.8   58.9 56.6  
Maternal educational level (%)     < 0.001    0.004
  < 9 years 47.4 43.4 56.0   48.1 46.6  
9–12 years 26.2 27.0 24.4   25.9 26.5  
  > 12 years 26.4 29.6 19.6   26.0 26.9  
Physical activity (Hours/day)
 IPA 0.21 (0.05, 0.57) 0.21 (0.02, 0.57) 0.23 (0.07, 0.57) 0.07 0.29 (0.07, 0.67) 0.19 (0.01, 0.48) < 0.001
 MPA 0.22 (0.00, 0.64) 0.23 (0.00, 0.64) 0.21 (0.00, 0.57) 0.21 0.25 (0.00, 0.67) 0.21 (0.00, 0.50) < 0.001
 Walking 0.48 (0.14, 1.00) 0.42 (0.00.14, 1) 0.50 (0.14, 1.00) < 0.001 0.50 (0.14, 1.00) 0.43 (0.14, 1.00) < 0.001
Sedentary behaviour (hours/week)
 TV watching 3.50 (1.75, 7.23) 5.25 (3.50, 8.17) 3.50(0.00, 7.00) < 0.001 4.67 (2.33, 8.17) 3.50 (1.17, 7.00) < 0.001
 PC game 2.33 (0.00, 7.00) 2.33 (0.00, 7.00) 3.50 (0.00, 7.00) < 0.001 3.50 (0.00, 7.00) 2.33 (0.00, 7.00) < 0.001
 Homework 12.25 (7.00, 17.50) 10.50 (7.00, 14.00) 15.75 (10.50, 21.00) < 0.001 10.50 (7.00, 17.50) 14.00 (7.00, 18.00) < 0.001
Sleep duration     < 0.001    < 0.001
LSD 25.3 35.0 6.7   26.5 24.1  
MSD 57.1 57.5 56.3   57.9 56.2  
SSD 17.6 7.5 37.1   15.6 19.7  
Diet intake (serves/week)
Sugar Beverage 1 (0, 3) 1(0, 2) 0 (2, 5) < 0.001 2 (0, 4) 1 (0, 2) < 0.001
Meat 1 (1, 19) 7 (3, 8) 7 (3, 10) < 0.001 7 (4, 12) 6 (3, 7) < 0.001
Fruits 7 (4, 14) 7 (5, 14) 7 (3, 12) < 0.001 7 (4, 12) 7 (4, 14) < 0.001
Vegetables 10 (7, 14) 10 (7, 14) 10 (7, 14) 0.41 10 (7, 12) 10 (7, 14) 0.27
  1. BMI Body mass index, IPA intensive physical activity, MPA moderate physical activity, LSD Long sleep duration, MSD Middle sleep duration, SSD Short sleep duration. Sample characteristics are presented as Mean ± Standard deviation (normally distributed, age, height, weight and BMI), Median with quartile (median, Q25 and Q75, including physical activity, sedentary behaviours and diet intake) and frequency (%, family income, maternal educational level and sleep duration)