Table 1 25(OH) D concentration in children aged 0–18 years old

Total

55,925

26.13 ± 12.30

Gender

< 0.001

 Boys

30,683 (54.86)

26.42 ± 12.07

 Girls

25,241 (45.13)

25.78 ± 12.56

Age (year)

< 0.001

 0 < age < 1

11,953 (21.37)

33.25 ± 13.64

 1 ≤ age < 3

14,901 (26.64)

30.71 ± 11.44

 3 ≤ age < 6

13,124 (23.47)

23.74 ± 9.37

 6 ≤ age < 12

12,416 (22.20)

19.12 ± 8.70

 12 ≤ age < 18

3531 (6.31)

16.24 ± 8.30

Season

< 0.001

 Spring

15,795 (28.24)

25.98 ± 11.77

 Summer

17,421 (31.15)

26.58 ± 13.07

 Autumn

10,205 (18.25)

26.51 ± 12.08

 Winter

12,504 (22.36)

25.37 ± 11.95

Ethnic

0.050

 Han

54,967 (98.29)

26.12 ± 12.29

 Ethnic minorities in China

958 (1.71)

26.91 ± 12.67

Outdoor time

< 0.001

  < 30 min/d

19,929 (35.63)

21.61 ± 11.81

 30–60 min/d

17,867 (31.95)

27.65 ± 11.47

  > 60 min/d

18,129 (32.42)

29.60 ± 12.11

BMI for age

< 0.001

 Normal

51,294 (91.72)

26.58 ± 12.26

 Overweight

2851 (5.10)

21.84 ± 12.43

 Obesity

1780 (3.18)

20.07 ± 9.90

Intervention

< 0.001

 None

28,328 (50.65)

20.60 ± 8.65

 Supplementation intervention

18,383 (32.87)

29.80 ± 9.49

 Therapeutic intervention

9214 (16.48)

35.80 ± 17.14