Table 1 Baseline characteristics between intervention and control groups of the study population

 N

26,591

24,327

 Boys (%)

50.76

50.77

-0.020

0.984

 Age(years)

10. 7(3.29)

10.92 (3.28)

-8.513

< 0.001

 City(%)

16,022(60.25)

14,907(61.28)

-2.364

0.018

Primary caregivers, n (%)

 Parents

23,037(89.23)

21,234(89.53)

-1.064

0.287

Socio-demographics, n (%)

 Only child

18,373(69.09)

16,430(67.54)

3.773

< 0.001

Father’s educational level

 Junior high school and below

9767(40.48)

10,457(47.14)

-17.312

< 0.001

 High School and Junior College

6646(27.55)

6141(27.68)

 College and above

7712(31.97)

5585(25.18)

Mother’s educational level

 Junior high school and below

10,697(44.39)

11,360(51.36)

-16.245

< 0.001

 High School and Junior College

6457(26.80)

5623(25.42)

 College and above

6943(28.81)

5138(23.23)

Father occupation

 Administrator and clerk

1614(8.33)

1118(6.38)

9.980

< 0.001

 Professional and technical

2958(15.27)

2475(14.13)

 Commerce and services

6673(34.44)

5762(32.90)

 Other

8128(41.96)

8158(46.58)

Mather occupation

 Administrator and clerk

772(3.75)

485(2.59)

9.600

< 0.001

 Professional and technical

2692(13.08)

2157(11.50)

 Commerce and services

7275(35.35)

6412(34.19)

 Other

9842(47.82)

9702(51.73)

Monthly household income (RMB)

 < 2000

2031(16.83)

2127(18.16)

-2.752

0.006

 2,000–5,000

5882(48.74)

5690(48.57)

 5,000–8,000

4156(34.44)

3898(33.27)