Vitamin D deficiency is common in rheumatoid arthritis (RA) and may be related to disease activity. Population-based studies have shown the influence of vitamin D deficiency on quality of life (QoL), but it was not investigated in RA patients.
The aim of the study was to determine possible relationship between vitamin D deficiency, QoL, physical activity (PA), and disease activity in RA.
In 97 consecutive RA patients without vitamin D supplementation (86 women and 11 men, aged 59.4 ± 12 years), serum 25-hydroxycholecalciferol (25(OH)D), calcium, phosphorus, and parathyroid hormone were measured. The patients completed Short Form 36 (SF-36), Beck Depression Inventory, and Health Assessment Questionnaire, assessed the intensity of pain, fatigue, and PA. Disease Activity Score in 28 Joints was used to assess disease activity. A comparison control group consisted of 28 osteoarthritis patients (25 women and 3 men aged 56.2 ± 15 years).
Vitamin D deficiency was detected in 76.3% of RA and in 78.6% of osteoarthritis patients (P = 0.75). There was a negative correlation between 25(OH)D serum concentration and Disease Activity Score in 28 Joints in patients with active arthritis. There was a positive correlation between serum 25(OH)D and the level of PA and most aspects of SF-36, and negative correlation between serum 25(OH)D and Health Assessment Questionnaire and Beck Depression Inventory in patients with disease duration of 1 year or longer. After inclusion of PA into multivariable analysis, only the correlations between 25(OH)D and SF-36 mental subscale (MCS) and pain remained significant.
Vitamin D deficiency is highly prevalent in RA patients and is associated with higher disease activity and worse QoL indices. Regular PA correlates with higher vitamin D titers and better QoL in RA. Further studies are needed to explain possible influence of vitamin D on RA activity.