Background/Purpose: Vitamin D (25[OH]D) insufficiency and deficiency is reported to be common in patients with rheumatoid arthritis (RA) and is associated with increased disease activity of RA, although there are limited reports of Japanese RA patients in the literature. Among osteoporosis patients treated with bisphosphonates, vitamin D status and concomitant use of active vitamin D3 analogs are both reported to affect the increase in bone mineral density (BMD). Our purpose was to define the prevalence and associations of 25(OH)D insufficiency and deficiency with clinical characteristics in Japanese patients with RA.

Methods: Serum 25(OH)D levels, laboratory data, and clinical data were obtained from 4,793 patients with RA (4,075 women, 718 men, mean age 59.7 years) who participated in the Institute of Rheumatology Rheumatoid Arthritis (IORRA) observational cohort study in April and May of 2011. Their serum vitamin D levels were evaluated using radioimmunoassays. Insufficiency was defined as a concentration < 20 ng/mL and deficiency as < 10 ng/mL. Associations of 25(OH)D insufficiency and deficiency with patient characteristics were examined using multivariate logistic regression.

Results: The mean (SD) serum 25(OH)D level was 16.9 (6.1) ng/mL. The prevalence of 25(OH)D insufficiency and deficiency among all the patients in the study were 71.8% and 11.5%, respectively. Serum 25(OH)D levels were significantly different (P < 0.05) between the patients with (n = 507, 10.6%) and without active vitamin D3 analogs. Among the patients treated with bisphosphonates (n = 1,130), insufficiency and deficiency were 71.5% and 10.4%, respectively. In multivariate analyses, female gender (odds ratios [OR] 2.38, 95 confidence interval [CI] 1.88-2.92 and OR 2.01, 95% CI 1.41-2.91), age (per 10 years, OR 0.72, 95% CI 0.68-0.77 and OR 0.67, 95% CI 0.62-0.73), Japanese health assessment questionnaire (J-HAQ) disability scores (OR 1.20, 95% CI 1.07-1.36 and OR 1.63, 95% CI 1.40-1.92), serum total cholesterol levels (per 10 mg/100mL, OR 0.96, 95% CI 0.94-0.98 and OR 0.95, 95% CI 0.92-0.98), serum alkaline phosphate level (per 10 IU/L, OR 1.01, 95% CI 1.00-1.02 and OR 1.02, 95% CI 1.00-1.03), and use of non-steroidal anti-inflammatory drugs (NSAIDs) (OR 1.27, 95% CI 1.11-1.46 and OR 1.25, 95% CI 1.02-1.54) were associated (P < 0.05) with vitamin D insufficiency and deficiency, respectively. Body mass index (BMI) and use of active vitamin D3 analogs (OR 0.96, 95% CI 0.93-0.99 and OR 0.69, 95% CI 0.48-0.97, respectively) were significantly associated with vitamin D deficiency alone. The Disease Activity Score including 28 joints (DAS28) was not significantly associated with either vitamin D insufficiency or deficiency in this patient population.

Conclusion: Vitamin D insufficiency and deficiency are common in Japanese patients with RA, as previously reported for patients of other ethnicities. Female gender, younger age, high HAQ disability score, serum levels of total cholesterol and alkaline phosphate and NSAID use appear to be associated with both vitamin D insufficiency and deficiency in Japanese patients with RA. Low BMI and disuse of active vitamin D3 analogs, however, appear to correlate only with vitamin D deficiency in Japanese patients with RA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/prevalence-and-associated-factors-of-vitamin-d-insufficiency-and-deficiency-in-4793-japanese-patients-with-rheumatoid-arthritis/