Characteristics of participants stratified by sex and vitamin D status*
| Characteristics† | Boys (n=3057) | Girls (n=3034) | ||||||
| Adequacy | Inadequacy | Deficiency | P value | Adequacy | Inadequacy | Deficiency | P value | |
| n | 760 | 1487 | 810 | 557 | 1441 | 1036 | ||
| Age, mean (SD), years | 11.66 (4.04) | 12.37 (3.71) | 12.74 (3.34) | <0.001 | 11.43 (4.05) | 12.75 (3.85) | 13.16 (3.42) | <0.001 |
| 25(OH)D, mean (SD), nmol/L | 61.13 (10.14) | 39.46 (5.55) | 23.00 (5.07) | <0.001 | 60.66 (10.00) | 39.11 (5.56) | 22.63 (5.05) | <0.001 |
| Season of blood collection, n (%) | <0.001 | <0.001 | ||||||
| Spring | 167 (22.0) | 505 (34.0) | 233 (28.8) | 111 (19.9) | 387 (26.9) | 292 (28.2) | ||
| Summer | 174 (22.9) | 154 (10.4) | 24 (3.0) | 158 (28.4) | 166 (11.5) | 47 (4.5) | ||
| Autumn | 349 (45.9) | 691 (46.5) | 452 (55.8) | 240 (43.1) | 756 (52.5) | 571 (55.1) | ||
| Winter | 70 (9.2) | 137 (9.2) | 101 (12.5) | 48 (8.6) | 132 (9.2) | 126 (12.2) | ||
| North, n (%) | 523 (68.8) | 1012 (68.1) | 567 (70.0) | 0.630 | 373 (67.0) | 895 (62.1) | 742 (71.6) | <0.001 |
| Smoking, n (%) | 74 (9.7) | 140 (9.4) | 92 (11.4) | 0.320 | 29 (5.2) | 73 (5.1) | 50 (4.8) | 0.938 |
| Drinking, n (%) | 162 (21.3) | 315 (21.2) | 191 (23.6) | 0.380 | 96 (17.2) | 259 (18.0) | 180 (17.4) | 0.894 |
| Ideal PA, n (%) | 243 (32.0) | 480 (32.3) | 222 (27.4) | 0.042 | 104 (18.7) | 279 (19.4) | 211 (20.4) | 0.690 |
| Ideal dietary vitamin D intake, n (%) | 60 (7.9) | 119 (8.0) | 52 (6.4) | 0.359 | 43 (7.7) | 82 (5.7) | 60 (5.8) | 0.207 |
| BMI, mean (SD), kg/m2 | 19.04 (3.95) | 20.22 (4.47) | 20.32 (4.72) | <0.001 | 18.30 (3.61) | 19.34 (3.79) | 19.52 (3.83) | <0.001 |
| FMP, geometric mean (95% CI), % | 25.4 (24.9 to 25.9) | 26.9 (26.5 to 27.3) | 26.3 (25.8 to 26.8) | <0.001 | 31.2 (30.7 to 31.7) | 32.6 (32.2 to 32.8) | 32.1 (31.7 to 32.5) | <0.001 |
| FMI, geometric mean (95% CI), kg/m2 | 4.76 (4.63 to 4.89) | 5.31 (5.20 to 5.43) | 5.20 (5.04 to 5.36) | <0.001 | 5.62 (5.47 to 5.78) | 6.22 (6.11 to 6.33) | 6.16 (6.03 to 6.29) | <0.001 |
| MMI, geometric mean (95% CI), kg/m2 | 13.1 (12.9 to 13.3) | 13.5 (13.4 to 13.6) | 13.7 (13.5 to 13.8) | <0.001 | 11.7 (11.5 to 11.8) | 12.1 (12.0 to 12.2) | 12.2 (12.1 to 12.4) | <0.001 |
| Obesity (including overweight), n (%) | 176 (23.2) | 483 (32.5) | 239 (29.5) | <0.001 | 88 (15.8) | 279 (19.4) | 195 (18.8) | 0.176 |
| Abdominal obesity, n (%) | 119 (15.7) | 339 (22.8) | 173 (21.4) | <0.001 | 46 (8.3) | 162 (11.2) | 116 (11.2) | 0.123 |
| Hypertension, n (%) | 161 (21.2) | 361 (24.3) | 184 (22.7) | 0.247 | 86 (15.4) | 337 (23.4) | 246 (23.7) | <0.001 |
| High TC, n (%) | 10 (1.3) | 41 (2.8) | 21 (2.6) | 0.090 | 15 (2.7) | 74 (5.1) | 50 (4.8) | 0.058 |
| High LDL-C, n (%) | 16 (2.1) | 51 (3.4) | 31 (3.8) | 0.122 | 12 (2.2) | 64 (4.4) | 35 (3.4) | 0.043 |
| High HDL-C, n (%) | 97 (12.8) | 214 (14.4) | 119 (14.7) | 0.482 | 7 (1.3) | 9 (0.6) | 5 (0.5) | 0.188 |
| High TG, n (%) | 28 (3.7) | 96 (6.5) | 72 (8.9) | <0.001 | 9 (1.6) | 25 (1.7) | 35 (3.4) | 0.013 |
| Hyperglycemia, n (%) | 277 (36.4) | 585 (39.3) | 318 (39.3) | 0.372 | 115 (20.6) | 385 (26.7) | 324 (31.3) | <0.001 |
| Insulin resistance, n (%) | 149 (19.6) | 338 (22.7) | 199 (24.6) | 0.058 | 116 (20.8) | 327 (22.7) | 259 (25.0) | 0.146 |
Data were presented as mean (SD), geometric mean (95% CI), or n (%).
*Vitamin D status was classified by the Institute of Medicine (IOM) recommendation: deficiency, <30 nmol/L; inadequacy, 30 to <50 nmol/L; adequacy, ≥50 nmol/L.20
†The diagnostic criteria are as follows: The weight status was classified as normal and obesity (including overweight) according to the International Obesity Task Force (IOTF) criteria14; Abdominal obesity was defined as waist to height ratio ≥0.515; Hypertension was classified by the 95th sex, age and height-specific blood pressure cut-points of Chinese standard16; Abnormal blood lipid levels were classified by the age and sex-specific lipoprotein cut-points of Chinese children17; Hyperglycemia was defined as fasting blood glucose ≥5.6 mmol/L18; Insulin resistance was defined by the WHO as values in the highest quartile of the homeostasis model assessment of insulin resistance (HOMA-IR).19
BMI, body mass index; FMI, fat mass index; FMP, fat mass percentage; HDL-C, high-density lipoprotein-cholesterol; LDL-C, low-density lipoprotein-cholesterol; MMI, muscle mass index; 25(OH)D, 25-hydroxyvitamin D; PA, physical activity; TC, total cholesterol; TG, triglyceride.