Table 1. Baseline characteristics of subjects according to urinary cotinine level.
|
Urinary cotinine level (ng/ml) |
||||
|---|---|---|---|---|
| T1 | T2 | T3 | P-value | |
| Unweighted (n) | 378 | 382 | 379 | – |
| Sex (male)a | 51.5 (3.2) | 53.6 (3.4) | 54.1 (3.1) | 0.848b |
| Age (years)c | 14.8±0.1 | 14.9±0.1 | 14.9±0.1 | 0.86d |
| Area of residence (rural)a | 16.3 (3.3) | 20.5 (3.7) | 13.6 (2.9) | 0.229b |
| Physical activity (yes)a | 27.3 (3.4) | 29.9 (3.2) | 32.5 (3.7) | 0.596b |
| Parental income level (the lowest quartile)a | 10.5 (2.1) | 14.5 (2.7) | 13.0 (3.7) | 0.6b |
| Receipt of national basic livelihood security (yes)a | 3.9 (1.3) | 5.6 (1.9) | 10.0 (3.6) | 0.152b |
| Height (cm)c | 164.6±0.6 | 163.5±0.6 | 164.5±0.7 | 0.363d |
| Body weight (kg)c | 56.3±0.9 | 57.1±0.8 | 57.3±1.2 | 0.748d |
| BMI (kg/m2)c | 20.6±0.2 | 21.2±0.2 | 21.0±0.3 | 0.221d |
| WC (cm)c | 69.8±0.7 | 70.7±0.7 | 70.4±0.9 | 0.664d |
| SE (diopter)c | −3.1±0.2 | −2.8±0.1 | −2.2±0.1 | 0.002d |
| 25(OH)D (ng/ml)c | 16.4±0.4 | 16.3±0.3 | 16.1±0.4 | 0.875d |
Abbreviations: 25(OH)D, 25-hydroxyvitamin D; ANOVA, analysis of variance; BMI, body mass index; SE, spherical equivalent; WC, waist circumference.
a
Values are shown as % (standard errors).
b
P-values were calculated by using χ2 test.
c
Values are shown as means±standard errors.
d
P-values were calculated by using analysis of variance test.