High prevalence of hypovitaminosis D of patients with autoimmune rheumatic diseases in China

We aimed to determine the prevalence of hypovitaminosis D in patients with autoimmune rheumatic diseases (ARDs) in China and its association with demographic characteristics of the patients. We recruited 384 patients in this cross-sectional study including 121 cases of systemic lupus erythematosus (SLE), 131 rheumatoid arthritis (RA), 102 spondyloarthritis (SpA) and 30 other ARDs. For each patient, demographic information was collected and serum concentration of 25OHD3 was measured by electrochemiluminescence immunoassay (ECLIA). The multivariate logistic regression model was used to investigate the association between vitamin D deficiency and patient characteristics. The mean serum vitamin D level of the 384 patients was 18.91 (8.12) ng/mL, and the median age was 37.33 (12.01) yrs. Among these patients, 222 (57.81%) and 127 (33.07%) were found to be vitamin D deficiency and insufficiency, respectively. From the disease perspective, the percentages of insufficiency and deficiency were as follow: 97.52% and 84.30% in SLE, 87.02% and 48.85% in RA, 88.24% and 40.20% in SpA, 90.89% and 57.81% in other ARDs patients. The causative factors for vitamin D deficiency included SLE per se (OR 12.54, P < 0.001) and high body mass index (BMI) (OR 1.88, P < 0.001). However, the seniors were less likely to have vitamin D deficiency (OR 0.95, P = 0.005). No correlation was disclosed between vitamin D deficiency and gender or disease duration. Hypovitaminosis D is highly prevalent among autoimmune rheumatic diseases population in China. The SLE per se and the obesity are the risk factors for vitamin D deficiency. Clinicians are advised to supplement vitamin D in these patients.