LAS VEGAS, NV—Low levels of vitamin D are related to chronic knee pain and vitamin D levels <25ng/mL may be a clinical threshold for treating vitamin D insufficiency in order to mitigate chronic pain, according to a study presented at PAINWeek 2012.

Chronic pain is one of several health conditions that have been correlated with vitamin D deficiency. Investigators have established vitamin D as a mediator of race differences in experimental pain. Currently, a clinically meaningful threshold value to associate vitamin D and chronic pain outcomes has not yet been determined. Toni L. Glover, ARNP, from University of Florida, Gainesville,  and colleagues conducted a study to determine a clinically useful vitamin D threshold that is predictive of chronic pain-related symptoms and of responses to evoked experimental pain.

This study enrolled 94 (75% female) middle-aged and older adults (mean age 56 years) with chronic knee pain. The subjects were racially diverse (48% African American/Black and 52% White) and community-dwelling. They were enrolled regardless of radiographic evidence of osteoarthritis. Vitamin D from serum was analyzed by high-performance liquid chromatography.

The study investigators concluded that a threshold level of <25ng/mL for vitamin D insufficiency was most effective to demonstrate differences both in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and in the threshold for pressure pain (PPT) as functions of vitamin D insufficiency. An increase in total WOMAC scores (F1, 90=5.46, P=0.02), indicating greater self-reported osteoarthritis symptoms (eg, pain, stiffness, and physical dysfunction), and a decrease in PPT (F1, 90=11.54, P=0.001), indicating increased pain sensitivity to mechanical stimulation, were associated with vitamin D levels <25ng/mL relative to levels >25ng/mL.