Table 1 General characteristics of participants in the study
| Â | Non- Thyroid Nodule | Thyroid Nodule | All |
|---|---|---|---|
(n = 6998) | (n = 3069) | (n = 10067) | |
Sex, male, n (%) | 3751 (53.6%) | 1478 (48.2%) | 5229 (51.9%) |
Age (years), mean (SD) | 10.8 (1.99) | 11.2 (1.99) | 11.0 (2.00) |
BMI (kg/m2), mean (SD) | 19.0 (4.12) | 19.2 (3.75) | 19.1 (4.01) |
Obesity | 1167(16.7%) | 472(15.4%) | 1639(16.3%) |
UIC (µg/L) |  |  |  |
 < 100 | 636 (9.1%) | 257 (8.4%) | 893 (8.9%) |
  [100, 199] | 2075 (29.7%) | 895 (29.2%) | 2970 (29.5%) |
  (199, 300) | 2138 (30.6%) | 1002 (32.6%) | 3140 (31.2%) |
 ≥ 300 | 2149 (30.7%) | 915 (29.8%) | 3064 (30.4%) |
WIC (µg/L) |  |  |  |
 < 40 | 6895 (98.5%) | 3012 (98.1%) | 9907 (98.4%) |
  [40, 100] | 103 (1.5%) | 57 (1.9%) | 160 (1.6%) |
Frequency of iodine-rich food intake | Â | Â | Â |
 Less than twice per month | 1852 (26.5%) | 820 (26.7%) | 2672 (26.5%) |
 Middle portion | 2847 (40.7%) | 1313 (42.8%) | 4160 (41.3%) |
 More than twice per week | 2299 (32.9%) | 936 (30.5%) | 3235 (32.1%) |
School | Â | Â | Â |
 Primary school | 3783 (54.1%) | 1361 (44.3%) | 5144 (51.1%) |
 Junior high school | 3215 (45.9%) | 1708 (55.7%) | 4923 (48.9%) |
Daily sleep time (hours) | Â | Â | Â |
 Q1, ≤8 | 2012 (28.8%) | 992 (32.3%) | 3004 (29.8%) |
 Q2, (8,9] | 2194 (31.4%) | 1059 (34.5%) | 3253 (32.3%) |
 Q3, (9,9.5] | 975 (13.9%) | 357 (11.6%) | 1332 (13.2%) |
 Q4, > 9.5 | 1817 (26.0%) | 661 (21.5%) | 2478 (24.6%) |
Time spent per day to complete homework (hours) | Â | Â | Â |
 Q1, ≤1 | 2727 (39.0%) | 1086 (35.4%) | 3813 (37.9%) |
 Q2, (1,2] | 2496 (35.7%) | 1149 (37.4%) | 3645 (36.2%) |
 Q3, (2,2.5] | 237 (3.4%) | 111 (3.6%) | 348 (3.5%) |
 Q4, > 2.5 | 1538 (22.0%) | 723 (23.6%) | 2261 (22.5%) |
Attending tutorial classes outside of school | Â | Â | Â |
 No | 3506 (50.1%) | 1365 (44.5%) | 4871 (48.4%) |
 Yes | 3492 (49.9%) | 1704 (55.5%) | 5196 (51.6%) |
Parental smoking status | Â | Â | Â |
 No | 5544 (79.2%) | 2461 (80.2%) | 8005 (79.5%) |
 Yes | 1454 (20.8%) | 608 (19.8%) | 2062 (20.5%) |