To evaluate the association between vitamin C supplementation and the incidence and progression of radiographic knee osteoarthritis (OA).
Prospective cohort study.
Clearwater Osteoarthritis Study (COS): (1988 to the present) a longitudinal study.
Male and female COS participants aged 40 years and above (n 1023). The study exposure was the participants’ self-reported history of vitamin C supplementation. The participants underwent biennial, sequential knee radiographs, which were assessed using the Kellgren–Lawrence ordinal scale to determine evidence of the study 2 outcomes: incident radiographic knee OA (RKOA) and progression of RKOA.
Individuals without baseline knee OA who self-reported vitamin C supplement usage were 11 % less likely to develop knee OA than were those individuals who self-reported no vitamin C supplement usage (risk ratio (RR) = 0·89, 95 % CI 0·85, 0·93). Among those participants with RKOA at baseline, vitamin C supplement usage did not demonstrate an association with RKOA progression (RR = 0·94, 95 % CI 0·79, 1·22).
In the present prospective cohort study, we found no evidence to support a protective role of vitamin C in the progression of knee OA. However, after controlling for confounding variables, these data suggest that vitamin C supplementation may indeed be beneficial in preventing incident knee OA. Given the massive public health burden of OA, the use of a simple, widely available and inexpensive supplement to potentially reduce the impact of this disease merits further consideration.
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