Inadequate Levels of Vitamin D Might Play Role in Chronic Pain

SAN FRANCISCO – In what may be the first study of the prevalence of vitamin D inadequacy in patients seeking treatment for chronic pain, those who were on opioids used significantly higher doses and had been taking opioids significantly longer if they had vitamin D inadequacy than if they had adequate vitamin D levels, Dr. W. Michael Hooten reported at the annual meeting of the American Society of Anesthesiologists.

Inadequate levels of vitamin D were detected in 26% of 267 patients admitted to a multidisciplinary pain rehabilitation center at a tertiary referral medical center from February through December of 2006. Of the 140 patients who were using opioids, 27% had inadequate levels of vitamin D, Dr. Hooten of the Mayo Clinic, Rochester, Minn., and his associates reported in a poster presentation.

“Vitamin D inadequacy may represent an underrecognized source of nociception and impaired neuromuscular functioning among patients with chronic pain,” he said.

In previous studies, inadequate levels of vitamin D have been associated with medication-refractory musculoskeletal pain and neuromuscular dysfunction.

In the current retrospective study, patients underwent vitamin D testing at admission, were questioned about opioid use, and completed the Short Form-36 Health Status Questionnaire (SF-36).

Serum 25-hydroxyvitamin D levels of 20 ng/mL or higher were considered adequate, and levels below 20 ng/mL were considered inadequate.

Both the adequate and inadequate vitamin D groups were nearly evenly split between opioid users and nonusers. Among 69 patients with vitamin D inadequacy, 38 were using opioids, and 31 were not. Among 198 patients with adequate vitamin D, 102 were using opioids and 96 were not.

Patients taking opioids used a mean morphine equivalent dose of 134 mg/day in the subgroup with vitamin D inadequacy and 70 mg/day in the subgroup with adequate vitamin D. Opioid users with inadequate vitamin D had been taking the medications for a mean of 71 months, compared with 44 months for opioid users with sufficient vitamin D.

The opioid users with inadequate vitamin D reported significantly worse health perceptions and physical functioning on the SF-36. Scores did not differ significantly between the vitamin D groups for bodily pain or “role-emotional.”

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