DO ANTIOXIDANT MICRONUTRIENTS PROTECT AGAINST THE DEVELOPMENT AND PROGRESSION OF KNEE OSTEOARTHRITIS

Objective. Cumulative damage to tissues, mediated by reactive oxygen s pecies, has been implicated as a pathway that leads to many of the deg enerative changes associated with aging, We hypothesized that increase d intake of antioxidant micronutrients might be associated with decrea sed rates of osteoarthritis (OA) in the knees, a common age-related di sorder. Methods. Participants in the Framingham Osteoarthritis Cohort Study underwent knee evaluations by radiography at examinations 18 (19 83-1985) and 22 (1992-1993), Usual dietary intake was assessed using t he Food Frequency Questionnaire, administered at examination 20 (1988- 1989). Knees without OA at baseline (Kellgren and Lawrence [K&L] grade less than or equal to 1) were classified as having incident OA if the y had a K&L grade greater than or equal to 2 at followup, Knees with O A at baseline were classified as having progressive OA if their score increased by greater than or equal to 1 at followup, Knees were also c lassified as having cartilage loss or osteophyte growth if their maxim al joint space narrowing or osteophyte growth score increased by great er than or equal to 1 (range 0-3). The association of vitamin C, beta carotene, and vitamin E intake, ranked in sex-specific tertiles, with incidence and progression of OA was compared with that of a panel of n onantioxidant vitamins, B-1, B-6, niacin, and folate, using logistic r egression and generalized estimation equations to adjust for correlati on between fellow knees. The lowest tertile for each dietary exposure was used as the referent category, Odds ratios (OR) were adjusted for age, sex, body mass index, weight change, knee injury, physical activi ty, energy intake, and health status. Results. Six hundred forty parti cipants received complete assessments. Incident and progressive OA occ urred in 81 and 68 knees, respectively. We found no significant associ ation of incident OA with any nutrient. A 3-fold reduction in risk of OA progression was found for both the middle tertile (adjusted OR = 0. 3, 95% confidence interval [95% CI] 0.1-0.8) and highest tertile (adju sted OR = 0.3, 95% CI 0.1-0.6) of vitamin C intake, This related predo minantly to a reduced risk of cartilage loss (adjusted OR = 0.3, 95% C I 0.1-0.8), Those with high vitamin C intake also had a reduced risk o f developing knee pain (adjusted OR = 0.3, 95% CI 0.1-0.8), A reductio n in risk of OA progression was seen for beta carotene (adjusted OR = 0.4, 95% CI 0.2-0.9) and vitamin E intake (adjusted OR = 0.7, 95% CI 0 .3-1.6), but was less consistent. No significant associations were obs erved for the nonantioxidant nutrients. Conclusion. High intake of ant ioxidant micronutrients, especially vitamin C, may reduce the risk of cartilage loss and disease progression in people with OA. We found no effect of antioxidant nutrients on incident OA. These preliminary find ings warrant confirmation.