Table 3. Variables associated with serum 25-hydroxyvitamin D concentrations (ng/mL) in backward elimination regression.
| Variables | β (SE) | P value | Ptrend |
|---|---|---|---|
| Age (yr) | 0.05 (0.02) | 0.035 | |
| Female sex | -1.10 (0.15) | <0.001 | |
| Body mass index (kg/m2) | 0.37 | ||
| Underweight (<18.5) | -0.42 (0.21) | 0.044 | |
| Normal (18.5-<23) | - (referent) | ||
| Overweight (23-<25) | 0.28 (0.19) | 0.14 | |
| Obese (≥25) | -0.56 (0.27) | 0.037 | |
| Waist circumference (cm) | |||
| Normal (M<90, F<85) | - (referent) | ||
| Abdominal obesity (M≥90, F≥85) | -0.76 (0.38) | 0.048 | |
| Physical activity* | <0.001 | ||
| Low | - (referent) | ||
| Moderate | 0.23 (0.14) | 0.09 | |
| High | 1.07 (0.24) | <0.001 | |
| Sedentary time (h/day), tertile† | 0.003 | ||
| 1 (low) | - (referent) | ||
| 2 | -0.12 (0.15) | 0.43 | |
| 3 (high) | -0.51 (0.17) | 0.003 | |
| Sunlight exposure (min/day) | |||
| <30 | - (referent) | ||
| ≥30 | 0.37 (0.17) | 0.032 | |
| Dairy intake | <0.001 | ||
| ≤2/week | - (referent) | ||
| 3-4/week | 0.29 (0.17) | 0.08 | |
| 5-6/week | 0.39 (0.22) | 0.07 | |
| ≥7/week | 0.58 (0.18) | 0.001 | |
| Fatty fish intake | 0.006 | ||
| ≤1/month | - (referent) | ||
| 2-3/month | 0.28 (0.18) | 0.13 | |
| 1-2/week | 0.35 (0.19) | 0.07 | |
| ≥3/week | 0.73 (0.25) | 0.004 | |
| Instant noodle intake | <0.001 | ||
| ≤1/month | - (referent) | ||
| 2-3/month | -0.41 (0.17) | 0.015 | |
| 1-2/week | -0.48 (0.18) | 0.007 | |
| ≥3/week | -0.79 (0.24) | 0.001 | |
| Sugar-sweetened beverage | 0.041 | ||
| ≤1/month | - (referent) | ||
| 2-3/month | -0.28 (0.16) | 0.08 | |
| 1-2/week | -0.18 (0.19) | 0.36 | |
| ≥3/week | -0.54 (0.23) | 0.020 | |
| Breakfast (day/week) | <0.001 | ||
| ≤3 | - (referent) | ||
| 4-6 | 0.71 (0.17) | <0.001 | |
| 7 | 1.04 (0.17) | <0.001 | |
| Supplement use vs. non-use | |||
| Vitamin D | 2.17 (0.39) | <0.001 | |
| Vitamin D and calcium combined | 0.95 (0.33) | 0.005 | |
| Multivitamin | 1.90 (0.14) | <0.001 | |
| Household income, quartile‡ | 0.58 | ||
| 1 (low) | - (referent) | ||
| 2 | -0.48 (0.17) | 0.006 | |
| 3 | 0.10 (0.22) | 0.65 | |
| 4 (high) | -0.10 (0.18) | 0.57 |
All variables were adjusted for the variables in the table mutually. *High: i) vigorous activity ≥3 day/wk and total physical activity≥1,500 MET-min/wk or ii) total physical activity ≥3,000 MET-min/wk; moderate: i)≥3 days of vigorous activity at least 20 min/d or ii)≥5 days of moderate activity and/or walking at least 30 min/d or iii)≥5 days of any combination of activities≥600 MET-min/wk; †Tertile: sedentary time (hr) ≤7, 8-10, ≥11; ‡Quartile: monthly family income (10,000 Korean Won)<170, 170-245, 246-374, ≥375.