Determinants and effects of vitamin D supplementation on serum 25-hydroxy-vitamin D levels in patients with rheumatoid arthritis

OBJECTIVES:Osteoporosis (OP) and increased risk of fracture are relevant features in patients with rheumatoid arthritis (RA). Low levels of serum vitamin D are frequently reported and correlate with a higher RA activity. This study evaluated factors related with the prescription of vitamin D supplements in RA patients and variables influencing the achievement of adequate vitamin D levels.METHODS:Study population was made up by 1168 consecutive RA patients from 22 Italian rheumatology centers. Demographic and clinical variables data were collected and 25OH serum vitamin D was measured in all patients. Insufficient serum 25OH vitamin D levels were defined as values lower than 20 ng/mL.RESULTS:The majority of patients (56.0%) was not taking vitamin D supplements. Among the 514 supplemented patients, 196 (38.1%) were taking insufficient dosages (≤440 IU/day). Variables related with the prescription of supplements were older age, female sex, previous bone density assessment and OP diagnosis. Among the 318 patients using daily supplements ≥800 IU, 88 patients (27.7%) did not reach adequate levels of vitamin D. In these patients a higher HAQ score (OR for 1 point=1.62, 95% CI: 1.06-2.49; p=0.03) and poor sun exposure (OR=2.38, 95% CI: 1.05-5.55; p=0.04) were predictors of vitamin D insufficiency.CONCLUSIONS:Vitamin D deficiency is common in patients with RA, even in patients who are regularly using supplements. Vitamin D supplementation is often ineffective even at the recommended dose of 800 IU/day in more disabled patients.