Association of serum carotenoids, retinol, and tocopherols with radiographic knee osteoarthritis: Possible risk factors in rural Japanese inhabitants

Background. The consumption of antioxidant nutrients may influence the development and progression of osteoarthritis (OA). To determine the association between serum antioxidants and radiographic knee osteoarthritis, we undertook a cross-sectional investigation in a community-based study in Japan. Methods. A total of 562 subjects (224 male, 338 female) ≥40 years of age were enrolled in the Comprehensive Health Examination Program (CHEP, Yakumo Study) from 2003 to 2005. Subjects were categorized to the OA group (n = 140) if either knee was graded as Kellgren-Lawrence (K-L) grade ≤2. The no-OA group was defined as showing radiographic findings of K-L 0 or 1 in either knee (n = 422). The serum levels of retinol, β/γ-tocopherols, α-tocopherol, zeaxanthin/lutein, canthaxanthin, cryptoxanthin, lycopene, α-carotene, and β-carotene were measured by high-performance liquid chromatography. The values of these antioxidants were divided into tertiles, and a logistic regression analysis was performed to analyze the association between them and radiographic knee OA, adjusting for potential confounders. Results. Logistic regression analysis showed that compared to the lowest tertile of β/γ-tocopherols the adjusted odds ratio (OR) was 0.52 [95% confidence interval (CI) 0.29-0.93] in the highest tertile; it also indicated a linear trend across tertiles. Furthermore, the adjusted OR was significantly decreased only in the middle tertile of a-tocopherol (OR 0.51, 95% CI 0.29-0.90). We reevaluated any independent association for these tocopherols after adjustment by entering them into the model simultaneously. The significance of β/γ-tocopherols was maintained. In contrast, no associations were found with any carotenoids or retinol. Conclusions. High serum values of β/γ-tocopherols were found to be significantly associated with a low OR for radiographic knee osteoarthritis. The decreasing risk with a high serum value of β/γ-tocopherols may support the possible protective effects against knee OA.