Vitamin D deficiency as a mediator of ethnic differences in experimental pain: preliminary findings

Abstract

Ethnic differences in quantitative sensory testing have previously been demonstrated along with separate studies showing greater vitamin D deficiency in ethnic minorities. While preliminary reports suggest that vitamin D deficiency is implicated in several health conditions, few studies have investigated whether ethnic differences in pain might be explained by differences in vitamin D levels. The purpose of this study was to examine whether vitamin D levels mediate ethnic differences in experimental pain. Serum was collected for vitamin D analyte (25-hydroxyvitamin D (25[OH]D). The sample consisted of 64 (68% female) ethnically diverse (63% Caucasian, 36% African American) community-dwelling middle-aged and older adults with a mean age of 57 years. Controlling for sex, age, and presence of knee pain, regression analysis revealed that ethnicity was significantly related to pressure pain threshold (β=.26; p=.04) and heat pain tolerance (β=.44; p<.001) but not heat pain threshold (β=.07; p=.58) assessed at the knee. In general, African Americans demonstrated greater pain sensitivity than their Caucasian counterparts. Further, ethnicity was significantly related to vitamin D level (β=.47; p<.001) with African Americans demonstrating greater vitamin D deficiency than Caucasians. Controlling for previously mentioned covariates and ethnicity, diminished vitamin D was significantly related to lower pressure pain thresholds (β=.29; p=.04) but not heat pain tolerance (β=.19; p=.17). Using a bias-corrected bootstrapped confidence interval, results showed that diminished vitamin D significantly mediated the relationship between ethnicity and pressure pain threshold (95% BC CI: .054 to .946 with 1000 resamples) assessed at the knee. To our knowledge, these data are the first to support that ethnic differences in pain are mediated by differences in vitamin D level. Vitamin D deficiency may be a risk factor for increased pain experience in African Americans. As data collection progresses, relationships between vitamin D levels, pain, and ethnicity will be more fully explored.