Stepwise multivariate analysis assessing the variance of serum 25-OHD levels in COPD
| Explanatory variables | Parameter estimate (β) (95% CI) | P value |
| Intercept | 15 (9.8 to 21) | <0.0001 |
| FEV1, % predicted | 0.087 (0.05 to 0.12) | <0.0001 |
| Seasonal variation | 1.9 (0.79 to 3.0) | 0.0009 |
| rs7041 variant | −4.5 (−6.5 to −2.4) | <0.0001 |
| Body mass index | −0.27 (−0.47 to −0.07) | 0.009 |
| KCO, % predicted | 0.043 (0.01 to 0.08) | 0.04 |
Only variables which contributed significantly to the variance of serum 25-OHD in patients with COPD (n=252) are shown. Non-significant variables were removed from the model and are not shown. These include: current smoking, current and previous use of oral corticosteroids, age, gender and rs4588 variants.
COPD, chronic obstructive pulmonary disease; FEV1, forced expiratory volume in 1 s; KCO, alveolar ventilation; 25-OHD, 25-hydroxyvitamin D.