Multivariate linear regression analysis of variables associated with serum 25(OH)D levels.
| Variable | Estimate | SE | p |
|---|---|---|---|
| Age | −0.30 | 0.13 | 0.02 |
| Vitamin D supplementation | < 0.0001 | ||
| None | −5.70 | 1.18 | < 0.0001 |
| ≤ 400 IU VD3 daily | −2.22 | 1.42 | 0.12 |
| > 400 IU VD3 daily | Reference group | ||
| Autoimmune disorder | −1.11 | 0.60 | 0.06 |
| Body mass index (nonobese) | 2.55 | 0.80 | 0.002 |
| Ethnicity (white) | 3.92 | 0.74 | < 0.0001 |
| Season | < 0.0001 | ||
| Fall | −0.26 | 1.06 | 0.80 |
| Winter | −3.64 | 0.92 | 0.0001 |
| Spring | −2.49 | 0.99 | 0.01 |
| Summer | Reference group |