A flurry of studies reported at the 2008 American College of Rheumatology meeting put vitamin D levels into the clinical spotlight in both osteoarthritis (OA) and systemic sclerosis (SSc). Several experts suggested that clinical trials of vitamin D supplementation are needed, in addition to the ongoing study being sponsored by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). “This study demonstrates significant associations between serum levels of vitamin D, which is obtained mainly from sun exposure, radiographic OA, and increases in knee cartilage volume which are best observed using the whole range of vitamin D rather than predefined cut-points. This implies that vitamin D supplementation may prevent and/or retard cartilage loss in knee osteoarthritis,” Dr.Ding said.
Changhai Ding, MD, and colleagues from the University of Tasmania in Australia reported a close association between serum levels of vitamin D and changes in both medial and lateral tibial cartilage volume in patients with knee OA.
The Australian researchers used T1-weighted fat-suppressed magnetic resonance imaging (MRI) on right knee of randomly selected subjects at baseline (n = 978; mean age, 62 years, range 51–81 years; 50% female) and 2.9 years later (n = 419). Knee medial and lateral tibial cartilage volume were measured. Serum 25-hydroxyvitamin D [25 OHD] was assessed by radioimmunoassay.
The mean 25 OHD level was 52.6 nmol/L at baseline and was associated with winter sun exposure. Baseline serum 25 OHD was significantly associated with knee cartilage volume at medial and lateral tibial sites, and vitamin D deficiency (defined as vitamin D of < 50 nmol/L, 45% prevalence) was associated with moderate-to-severe joint space narrowing in the medial tibiofemoral compartment at both knees and negatively with knee cartilage volume at both medial and lateral tibial sites. Over 2.9 years, vitamin D deficiency predicted loss of medial tibial but not lateral tibial cartilage volume, but vitamin D levels as a continuous variable were significantly associated with changes in both medial and lateral tibial cartilage volume. Changes in vitamin D levels were positively associated with change in medial tibial cartilage volume.
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