To study the association between baseline vitamin D status, bone mineral density (BMD), and the development of radiographic osteoarthritis (ROA) of the knee in a large population-based cohort of men and women.
A sample of 1248 subjects (728 women and 520 men) was drawn from the Rotterdam Study, a prospective population-based cohort study of the elderly. At baseline, vitamin D dietary intake was determined, and BMD and 25-hydroxy vitamin D (25(OH)D) serum levels were measured. After a mean follow-up time of 6.5 years incidence and progression of knee ROA of was assessed.
The mean vitamin D intake in our study population was 64 IU/d and the mean 25(OH)D level 66 nmol/L. Vitamin D levels were associated with baseline BMD, particularly in subjects with baseline knee ROA. Progressive ROA occurred in 5.1% of the participants in the highest tertile of vitamin D intake against 12.6% in the lowest tertile, resulting in an adjusted odds ratio of 7.7 (95% CI: 1.3–43.5). Both intake and levels of 25(OH)D were not significantly related to incident ROA. However, we found a significant interaction between vitamin D intake and BMD in the association with incident knee ROA (P = 0.03): in subjects with low lumbar spine BMD at baseline we observe an increasing incidence of knee ROA with decreasing vitamin D intake and serum levels.
Low dietary vitamin D intake increases the risk of progression of knee ROA. Particularly in subjects with low baseline BMD, vitamin D status seems to influence the incidence and progression of knee ROA. Thus, improving the vitamin D status in the elderly could protect against the development and worsening of knee OA, especially in those with low BMD.
In this study of complex relations among vitamin D, BMD, and radiographic OA, low vitamin D intake and serum levels seemed to influence incidence and progression of OA in subjects with low baseline BMD.
From the *Departments of Internal Medicine, †Epidemiology and Biostatistics, and ‡Orthopedics, Erasmus Medical Center, Rotterdam, The Netherlands.
Supported by The Netherlands Organization for Scientific Research (NWO), grant numbers: 925-01-010, 014-90-001 and 903-46-178.
Correspondence: André G. Uitterlinden, PhD, Genetic Laboratory, Room Ee575, Department of Internal Medicine, Erasmus MC, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands. E-mail: firstname.lastname@example.org