Vitamin D deficiency in rheumatoid arthritis. Prevalence and association with disease activity in Western Saudi Arabia

To estimate the prevalence of low serum vitamin D level (25[OH]D) in patients with rheumatoid arthritis (RA) compared with healthy controls, and to analyze the association between 25(OH)D and disease activity. This retrospective analysis included 100 RA patients (85% women) and 100 controls, not on vitamin D supplements from January 2010 to December 2011 at a tertiary care center at the Department of Internal Medicine, King Abdulaziz University Hospital (KAUH), Jeddah, Kingdom of Saudi Arabia. Disease activity was measured using the disease activity score index (DAS28). According to the DAS28 score, RA patients were divided into 3 groups as high, moderate, and low disease activity. Patients' serum 25(OH)D was measured in a centralized laboratory. The mean 25(OH)D in patients with RA was similar to the control group (32.3+/-14.4 nmol/L) versus (31.4+/-16.4 nmol/L) (p=0.41). Patients with high disease activity had the lowest 25(OH)D levels (18.25+/-8.3 nmol/L) compared with patients with moderate (35.13+/-15.2 nmol/L) and low (38.05+/-7.3 nmol/L) disease activity (p