The purpose of this study was to determine the relationship of serum levels of 25-vitamin D and 1,25-vitamin D to incident changes of radiographic hip osteoarthritis (OA) among elderly white women.
Baseline and followup hip radiographs of 237 subjects were obtained an average of 8 years apart. Hips were scored for individual radiographic features (IRF) and assigned a summary grade based on the number and type of IRF present. Serum 25- and 1,25-vitamin D levels from baseline samples were analyzed by radioimmunoassay. Logistic and linear regression were used to examine the association of 25- and 1,25-vitamin D levels with radiographic changes, adjusting for age, health status, physical activity, weight, vitamin D supplement use, and calcaneal bone mineral density.
The risk of incident hip OA defined as the development of definite joint space narrowing was increased for subjects who were in the middle (odds ratio [OR] 3.21, 95% confidence interval [95% CI] 1.06, 9.68) and lowest (OR 3.34, 95% CI 1.13, 9.86) tertiles for 25-vitamin D compared with subjects in the highest tertile. Vitamin D levels were not associated with incident hip OA defined as the development of definite osteophytes or new disease according to the summary grade. No association between serum 1,25-vitamin D and changes in radiographic hip OA was found.
Low serum levels of 25-vitamin D may be associated with incident changes of radiographic hip OA characterized by joint space narrowing.