Supplementary information table 1. Multiple linear regression analyses of the cross-sectional association between serum 25(OH)D and candidate biomarkers in the Inter99 study.

b x 102 (95% CI) per 25 nmol/l 25(OH)D, p value
Outcomes (log-transformed) / crude / Adjusted 1 / Adjusted 2
Adiponectin / 5.73 (3.76;7.69)
P<0.001 / 5.32 (3.41;7.24)
P<0.001 / 4.86 (2.79;6.94)
P<0.001
C-reactive protein, pentraxin-related / -6.77 (-10.0;-3.54)
P<0.001 / -3.41 (-6.58;-0.25)
P=0.035 / -0.35 (-3.75;3.05)
P=0.84
Ferritin / -2.23 (-5.15;0.68)
P=0.13 / 1.24 (-1.39;3.86)
P=0.36 / 1.78 (-1.07;4.63)
P=0.22
Heat shock 70kDa protein 1B / -6.65 (-7.84;-5.47)
P<0.001 / -6.47 (-7-70;-5.23)
P<0.001 / -5.42 (-6.73;-4.09)
P<0.001
Insulin-like growth factor binding protein 1 / 4.98 (2.77;7.19)
P<0.001 / 0.03 (-2.07;2.12)
P=0.98 / 0.51 (-1.75;2.78)
P=0.66
Insulin-like growth factor binding protein 2 / 5.48 (3.28;7.68)
P<0.001 / 3.89 (1.70;6.09)
P<0.001 / 4.72 (2.36;7.08)
P<0.001
Interleukin 18 / -1.03 (-2.09;0.04)
P=0.058 / -0.02 (-1.11;1.06)
P=0.97 / 0.79 (-0.39;1.07)
P=0.19
Interleukin 2 receptor, alpha / -0.80 (-1.66;0.06)
P=0.068 / -0.31 (-1.20;0.58)
P=0.50 / 0.74 (-0.19;1.67)
P=0.12
Leptin (obesity homolog, mouse) / -2.68 (-5.39;0.02)
P=0.052 / -0.06 (-1.99;1.86)
P=0.95 / 0.30 (-1.77;2.37)
P=0.78

Abbreviations 25(OH)D 25-hydroxy-vitamin-D, CI confidence interval.

Model 1: Adjusted for age, sex, BMI, family history of diabetes, season of blood collection.

Model 2: Adjusted for sex, age, BMI, family history of diabetes, season of blood collection, leisure time physical activity, smoking status, alcohol consumption, dietary habits, total energy intake, and social class.

Due to natural log-transformation of the outcome variables, the b coefficients can be interpreted as the relative difference per one unit change in the exposure variable. Thus b x 102 can be interpreted as the percentage difference associated with a 25 nmol/l increase in 25(OH)D.

A non-linear relationship between 25(OH)D and heat shock 70kDa protein 1B was observed i.e. 25(OH)D squared was significant (data not shown).