The association between serum 25-hydroxyvitamin D levels and psoriasis in a large population-based cohort, a cross-sectional analysis of The Tromsø Study 2015-16.

This large population-based study found no significant relationship between 25(OH)D and psoriasis. The analysis may have been underpowered to detect a threshold effect in the lower 25(OH)D spectrum. Interaction analysis indicates that high BMI and vitamin D deficiency combined increase the odds of active psoriasis more than the sum of them, with an estimated 92% higher odds for active psoriasis in subjects with BMI>27.5 kg/m2 and 25(OH)D<25 nmol/L. Providing advice to prevent vitamin D deficiency may be considered in the follow-up of overweigth patients with psoriasis.