Table 4.

The association between DBP and demographics, vitamin D metabolites and other laboratory parameters.

	Difference in serum DBP mean (s.d.) (mg/L)	Correlation with serum DBP	P-value
Demographics
Age		r = −0.068	0.115
Women vs men	265.4 ± 87.8 vs 245.0 ± 71.5		0.005
Women <age of 50 years vs women ≥age 50 years	269.3 ± 93.0 vs 250.5 ± 62.6		0.116
Users of contraceptives vs non-users among women ≤50 years	328.5 ± 122.9 vs 261.0 ± 85.3		0.023
BMI		r = −0.107	0.013
Smokers vs non-smokers	261.1 ± 59.4 vs 252.7 ± 79.7		0.613
Vitamin D metabolites
Total serum 25(OH)D		r = 0.192	<0.001
Directly measured free 25(OH)D		r = 0.049	0.225
Calculated free 25(OH)D		r = −0.452	<0.001
1,25(OH)2D		r = 0.144	0.001
iPTH		r = −0.149	<0.001
Other laboratory parameters
Testosterone (men only)		r = −0.062	0.265
Estradiol (women only)		r = −0.046	0.532
SHBG		r = 0.268	<0.001
hsCRP		rS = 0.102	0.017
ALT		r = −0.035	0.421
Creatinine		r = −0.043	0.314
Albumin		r = −0.013	0.762

1,25(OH)₂D, 1,25-dihydroxy vitamin D; 25(OH)D, 25-hydroxy vitamin D; ALT, alanine aminotransferase; BMI, body mass index; DBP, vitamin D binding protein; HRT, hormone replacement therapy; hsCRP, highly sensitive c-reactive protein; iPTH, intact parathyroid hormone; r, Pearson correlation coefficient; r_S, Spearman correlation coefficient; SHBG, sexual hormone binding globulin.