NB–UV-B improves vitamin D status in psoriasis patients
MedWire News: Narrowband ultraviolet-B (NB-UV-B) treatment appears to increase serum levels of 25-hydroxyvitamin D (25(OH)D) as well as clear psoriasis, research suggests, with the number of exposures determining the magnitude of increase.
Caitriona Ryan and colleagues from St Vincent's University Hospital in Dublin, Ireland, note, however, that increases in serum 25(OH)D level did not correlate with treatment response in the 29 Irish patients treated with NB-UV-B.
"We cannot conclude, therefore, that NB-UV-B mediates its therapeutic effects by increasing vitamin D levels," they say in the Archives of Dermatology.
"This suggests that the improvement in both vitamin D status and psoriasis are contemporaneous, but unrelated, consequences of NB-UV-B, or that there is another explanation for the causal relationship."
The researchers measured 25(OH)D levels in 29 psoriasis patients who received NB-UV-B treatment three times per week and 29 psoriasis patients who received topical treatment or systemic agents, or no treatment, who acted as controls. The patients were recruited in the winter and control patients were recruited within 1 week of treated patients to control for seasonal variation of serum 25(OH)D levels.
NB-UV-B was administered until psoriasis cleared, defined as complete resolution of psoriasis or minimal residual activity of psoriasis (<1% body surface area).
Levels of serum 25(OH)D increased significantly in patients receiving NB-UV-B, from a median of 23 ng/ml to 59 ng/ml at the end of treatment, whereas there was no change in control patients.
During NB-UV-B treatment, Psoriasis Area and Severity Index (PASI) scores decreased significantly, from 7.1 at baseline to 0.5, and the median Dermatology Life Quality Index fell significantly from 10 to 1.Again, there was no significant change in control patients.
Despite this improvement in psoriasis, changes in serum 25(OH)D levels correlated only with number of exposures of NB-UV-B and cumulative UV-B dose, and not with treatment response. Also, the number of previous phototherapysessions was the only predictor of baseline serum 25(OH)D levels.
The researchers note that at the end of the study, all patients receiving NB-UV-B were vitamin D sufficient, whereas 75% of control patients were vitamin D insufficient, at levels below 20 ng/ml, during the wintertime.
This highlights the need "for seasonal supplementation to prevent the deleterious effects of hypovitaminosis D in this population unless phototherapy is being administered," they say.
In a related editorial, PanitaVemulapalli and Henry Lim, from Henry Ford Medical Center in Detroit, Michigan, USA, pointed out, however, that, "because of the known carcinogenic effect of UV, it is not appropriate to recommend exposure to natural or artificial UV as a means of achieving adequate vitamin D status."
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By Lucy Piper