Psoriatic arthritis patients lack vitamin D
MedWire News: There is a high prevalence of vitamin D insufficiency and deficiency among people with psoriatic arthritis (PsA), study findings show.
However, the results reveal no significant differences in PsA patients' vitamin D levels between summer and winter, or among those living in high latitude versus those living in low latitude areas.
Furthermore, despite previous research indicating an overall immunosuppressive effect of vitamin D, the researchers found no association between PsA disease activity and vitamin D levels.
"Additional research is required to elucidate if the vitamin D intake needed to achieve and maintain optimal vitamin D levels in PsA patients is greater than that recommended for the general population," suggest Dafna Gladman, from Toronto Western Hospital in Ontario, Canada, and colleagues in the journal Arthritis Care and Research.
Between March and August 2009, the team collected data for 302 PsA patients from the University of Toronto (northern latitude) and the "Lin" Medical Centre and Carmel Medical Centre in Haifa, Israel. The majority of patients were assessed during summer and winter. Vitamin D levels, employment status, disease function, dietary intake, and skin type were evaluated.
The current recommended concentration of serum 25-hydroxyvitamin (OH)D levels (vitamin D) is above 75 nmol/l; in this study the researchers defined insufficiency as 30-74 nmol/l and deficiency as under 30 nmol/l.
In the northern center, mean 25(OH)D levels were 70.3 and 73.9 nmol/l in the summer and winter, respectively, and in the southern center, the corresponding levels were 65.7 and 67.3 nmol/l.
Overall, 25(OH)D levels were sufficient in just 41.4% of patients in the summer and 41.3% of patients in the winter at the northern site, and in only 35.1% of patients in the summer and 42.1% of patients in the winter in the southern site.
These results represent a high prevalence of vitamin D insufficiency and deficiency among PsA patients, report the researchers, but do not indicate a significant difference by season or latitude.
Additionally, vitamin D levels did not differ significantly by race, employment status, skin type, or other demographic characteristics studied. Indeed, joint pain and Psoriasis Area and Severity Index scores were also similar between seasons.
"We aimed to raise the awareness of vitamin D insufficiency/deficiency in this group of patients and understand whether there is a seasonal variation," write Gladman et al.
"We report that the prevalence… is high in PsA patients, as has been demonstrated in other rheumatologic diseases," they conclude.
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By Sarah Guy