a1 Department of Epidemiology, College of Public Health, University of South Florida, Clearwater, FL, USA
a2 Department of Epidemiology, College of Public Health, The Arthritis Research Institute of America, University of South Florida, 300 S. Duncan Avenue Suite 188, Clearwater, FL 33755, USA
Objective To evaluate the association between vitamin C supplementation and the incidence and progression of radiographic knee osteoarthritis (OA).
Design Prospective cohort study.
Setting Clearwater Osteoarthritis Study (COS): (1988 to the present) a longitudinal study.
Subjects 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.
Results 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).
Conclusions 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.
(Received July 03 2009)
(Accepted May 13 2010)
(Online publication August 16 2010)