25-Hydroxyvitamin D and osteoarthritis: A meta-analysis including new data.

Objectives: To study the relationship between 25-hydroxy (OH) vitamin D serum levels and osteoarthritis (OA) of the knee, hip, and hand in a meta-analysis, with updated and expanded results of our previous study.

Methods: Pubmed was searched from February 1975 to December 2014 for articles assessing the relationship between vitamin D levels and OA. In our meta-analysis, 6 cross-sectional and 6 longitudinal studies were included. The number of subjects in these studies ranged from 99 to 1248 subjects. The latter 1248 subjects (58% women) were drawn from the Rotterdam Study, a prospective population-based cohort study of the elderly. At baseline, 25(OH) vitamin D serum levels were measured and prevalent OA of knees, hips and hands was scored by the Kellgren-Lawrence grading system. After a mean follow-up time was 8.4 years, incidence and progression of OA were assessed.

Results: No clear association between vitamin serum levels and prevalent, incident or progressive knee, hip or hand OA was observed. The quality of most studies was low, and the results were conflicting. Meta-analysis of 3 cross-sectional studies on vitamin D levels and knee joint space narrowing (JSN) showed an increased risk of prevalent JSN with decreasing vitamin D levels (OR = 1.52, 95% CI: 1.15-2.01). The association observed in the meta-analysis of 3 studies on low vitamin D levels and incident and progressive knee OA was not significant (OR = 1.37, 95% CI: 0.97-1.92); however, when considering solely progressive knee OA, the risk was significantly increased (OR = 2.40, 95% CI: 1.22-4.72).

Conclusions: Epidemiological studies do not provide evidence of an independent association between 25(OH) vitamin D serum levels with hip or hand OA. When analyzing subgroups of knee OA, significant associations of low vitamin D levels with prevalent knee JSN and with progressive knee OA were observed. Overall, the results of this study do not support the advice to supplement vitamin D to prevent the onset or worsening of osteoarthritis, except perhaps for progressive knee OA.