TABLE 1.
The demographic characteristics of the study population by the year.
| Variables | 2014 (n = 1,518) |
2016 (n = 1,013) |
2018 (n = 848) |
| Adolescents’ characteristics | |||
| Age in 2014, median (IQR) | 11.00 (10.00,15.00) | 11.00 (10.00,15.00) | 11.00 (10.00,13.00) |
| Gender (Female), no. (%) | 815 (53.69) | 535 (52.81) | 436 (51.42) |
| Parents’ characteristics | |||
| Maternal age in 2014, median (IQR) | 38.00 (35.00,42.00) | – | – |
| Paternal age in 2014, median (IQR) | 40.00 (37.00,44.00) | 41.00 (37.00,44.00) | 40.00 (37.00,44.00) |
| Maternal education level in 2014, median (IQR) | 7.00 (4.00,9.00) | 6.00 (4.00,9.00) | 8.00 (4.00,9.00) |
| Paternal education level in 2014, median (IQR) | 9.00 (6.00,9.00) | – | – |
| Mother was employed in 2014, no. (%) | 1,070 (85.88) | 753 (86.25) | 639 (87.53) |
| Father was employed in 2014, no. (%) | 1,157 (95.86) | 776 (96.64) | 640 (95.52) |
| Household characteristics | |||
| Lived in urban area in 2014, no. (%) | 611 (40.79) | 404 (40.36) | 347 (41.56) |
| Household per capita income in 2014 (CNY), median (IQR) | 8,012.50 (3,907.14, 13,760.00) | 7,944.45 (3,747.50, 13,177.50) | 8,159.0 (3,987.500, 13,937.50) |
| Family size in 2014, median (IQR) | 5.00 (4.00, 6.00) | – | – |