FRI0528 Long-term effects of vitamin d supplementation and maintaining vitamin d sufficiency on knee osteoarthritis over 5 years
Authors: B.S. Eathakkattu Antony, S. Zheng, J. Burgess, C. Ding
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Epidemiological studies suggest that vitamin D deficiency is associated with knee symptoms and structural progression of knee osteoarthritis (OA). However, randomised controlled trials (RCTs) failed to demonstrate a significant effect of vitamin D supplementation on OA, probably due to selecting OA participants with and without vitamin D deficiency, short duration of follow-up and a large proportion of participants in the placebo group reaching vitamin D sufficiency (61.3% of patients in the placebo group achieved a serum 25(OH)D level of &gt;60 nmol/L at 3 months of a clinical trial). <h3>Objectives</h3> To examine whether those maintaining sufficient serum vitamin D levels over 5 years had reduced knee symptoms compared with those who did not maintain adequate vitamin D levels in patients with knee OA. We also explored the effect of 2 year vitamin D supplementation on knee symptoms compared to placebo after 3 years of cessation of treatment. <h3>Methods</h3> Participants with symptomatic knee OA and low 25-hydroxyvitamin D [25(OH)D] (12.5–60 nmol/L) were randomly assigned to receive monthly treatment with oral vitamin D3 (50 000 IU; n=209) or an identical placebo (n=204) for 2 years. 172 participants who enrolled in the study from Hobart were followed up after 3 years (5 years from baseline) of the cessation of the treatment to assess knee symptoms and vitamin D levels. Participants were classified as maintaining sufficient vitamin D group if they maintained serum 25(OH)D&gt;50 nmol/L at month 3, 24 and 60 (n=79), and not maintaining sufficient vitamin D group (25(OH)D≤50 nmol/L at month 3, 26 and 60, n=62) groups. Knee symptoms were assessed at baseline, 3, 6, 12, 24 and 60 month using Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). <h3>Results</h3> The level of 25(OH)D dropped in the vitamin D group (87.0 nmol/L to 53.3 nmol/L) and slightly increased (53.3 nmol/L to 61.7 nmol/L) in the placebo group 3 years after the cessation of the treatment. Knee pain increased from the end of the study to 5 years of follow-up in the treatment (81.8 to 91.7) and placebo (75.8 to 101.1) groups. 16.7% of the participants in vitamin D and 18.5% of the participants in placebo group underwent total knee replacement (TKR) surgery. There were no significant differences in WOMAC symptoms, TKR rates or change in symptoms between Vitamin D and placebo groups after 3 years of cessation of the supplementation. Participants who maintained adequate vitamin D levels over 5 years had significantly less WOMAC knee pain (β:−38.4, 95% CI:−69.2,–7.7) and physical dysfunction (β:−98.5, 95% CI:−193.8,–3.1) than participants with vitamin D deficiency over 5 years in multivariable analyses. <h3>Conclusions</h3> Vitamin D supplementation over 2 years did not result in significant differences in change in knee symptom score over 5 years compared to placebo. However, knee OA patients maintaining sufficient serum vitamin D levels over long-term had more improvement in knee pain and physical function than those who did not maintain adequate vitamin D levels, suggesting a beneficial effect of maintaining sufficient serum vitamin D for knee OA. <h3>Disclosure of Interest</h3> None declared