Table 3.
Associations of various characteristics with VDBP, total, non-bioavailable, bioavailable, and free 25(OH)D concentrations: results of multiple linear regression.
| Characteristics | Group | VDBP | Total 25(OH)D | Non-Bioavailable 25(OH)D | Bioavailable 25(OH)D | Free 25(OH)D |
|---|---|---|---|---|---|---|
| Estimate (SE) | Estimate (SE) | Estimate (SE) | Estimate (SE) | Estimate (SE) | ||
| Age | <60 years | Ref | Ref | Ref | Ref | Ref |
| 60–64 years | −4.54 (2.14) | −0.51 (0.71) | −0.46 (0.62) | −0.02 (0.04) | −0.01 (0.09) | |
| 65–69 years | −9.03 (2.26) | −3.27 (0.74) | −3.00 (0.65) | −0.11 (0.04) | −0.16 (0.09) | |
| ≥70 years | −14.88 (2.61) | −5.59 (0.86) | −5.10 (0.75) | −0.20 (0.05) | −0.33 (0.11) | |
| Sex | Females | Ref | Ref | Ref | Ref | Ref |
| Males | −15.48 (1.86) | 7.82 (0.61) | 6.43 (0.53) | 0.55 (0.04) | 1.11 (0.08) | |
| School education | ≤9 years | Ref | Ref | Ref | Ref | Ref |
| 10–11 years | −4.21 (2.43) | 1.51 (0.79) | 1.26 (0.70) | 0.10 (0.05) | 0.18 (0.10) | |
| ≥12 years | 0.09 (2.68) | −0.77 (0.88) | −0.74 (0.77) | −0.01 (0.05) | −0.08 (0.11) | |
| Smoking status | Never smokers | Ref | Ref | Ref | Ref | Ref |
| Former smokers | 2.13 (2.04) | 1.28 (0.66) | 1.12 (0.58) | 0.06 (0.04) | 0.16 (0.08) | |
| Current smokers | 0.05 (2.50) | −5.54 (0.79) | −4.84 (0.70) | −0.28 (0.05) | −0.57 (0.10) | |
| Physical activity | Low | Ref | Ref | Ref | Ref | Ref |
| Moderate/high | 1.98 (1.79) | 3.33 (0.59) | 2.88 (0.52) | 0.18 (0.03) | 0.38 (0.08) | |
| Regular multivitamin intake | No | Ref | Ref | Ref | Ref | Ref |
| Yes | 6.87 (2.37) | 3.84 (0.78) | 3.50 (0.68) | 0.14 (0.05) | 0.32 (0.10) | |
| Fish consumption | <1 time/week | Ref | Ref | Ref | Ref | Ref |
| ≥1 time/week | 2.39 (1.80) | 0.43 (0.59) | 0.42 (0.51) | 0.01 (0.03) | 0.03 (0.07) | |
| Hypertension | No | Ref | Ref | Ref | Ref | Ref |
| Yes | 0.99 (1.71) | −0.31 (0.57) | −0.25 (0.50) | −0.02 (0.03) | −0.10 (0.07) | |
| Diabetes | No | Ref | Ref | Ref | Ref | Ref |
| Yes | −10.84 (2.40) | −2.40 (0.79) | −2.22 (0.69) | −0.07 (0.05) | −0.17 (0.10) | |
| Cardiovascular disease | No | Ref | Ref | Ref | Ref | Ref |
| Yes | −1.29 (2.16) | −0.85 (0.71) | −0.74 (0.62) | −0.04 (0.04) | −0.10 (0.09) | |
| Cancer | No | Ref | Ref | Ref | Ref | Ref |
| Yes | 2.85 (3.05) | −0.18 (1.01) | −0.10 (0.88) | −0.03 (0.06) | −0.08 (0.13) | |
| Chronic kidney disease | No | Ref | Ref | Ref | Ref | Ref |
| Yes | 4.59 (3.04) | 0.75 (1.01) | 0.67 (0.88) | 0.03 (0.06) | 0.11 (0.13) | |
| Body mass index | <25 kg/m2 | Ref | Ref | Ref | Ref | Ref |
| 25–29.9 kg/m2 | −8.21 (2.01) | −1.69 (0.66) | −1.60 (0.58) | −0.04 (0.04) | −0.07 (0.08) | |
| 30–34.9 kg/m2 | −13.69 (2.52) | −4.63 (0.83) | −4.27 (0.73) | −0.14 (0.05) | −0.31 (0.11) | |
| ≥35 kg/m2 | −26.31 (3.88) | −8.92 (1.28) | −8.11 (1.12) | −0.32 (0.07) | −0.61 (0.16) | |
| Total cholesterol | <200 mg/dL | Ref | Ref | Ref | Ref | Ref |
| ≥200 mg/dL | 13.19 (1.97) | −1.22 (0.65) | −1.00 (0.57) | −0.09 (0.04) | −0.34 (0.08) | |
| C-reactive protein | <3 mg/L | Ref | Ref | Ref | Ref | Ref |
| ≥3 mg/L | 17.86 (1.75) | 1.04 (0.58) | 1.27 (0.51) | −0.09 (0.03) | −0.10 (0.07) |
Bold print indicates p < 0.05. Abbreviations: SE: standard error; VDBP: vitamin D binding protein. The regression models were also adjusted for VDBP genotypes and seasons of blood draw.