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Objective: Vitamin D inadequacy is associated with analgesic medication refractory musculoskeletal pain and neuromuscular dysfunction. This vitamin deficiency could subsist as an unrecognized comorbid condition among patients with chronic pain. A fundamental barrier toward determining the relevance of vitamin D inadequacy to the clinical practice of pain medicine pertains to the unknown prevalence of this vitamin deficiency among patients with chronic pain. The primary objective of this study was to determine the prevalence and clinical correlates of vitamin D inadequacy in patients seeking treatment for chronic pain of diverse etiologies.

Methods: The retrospective case series involved 267 patients with chronic pain of diverse etiologies admitted to a multidisciplinary pain rehabilitation center at a tertiary referral medical center from February 2006 through December 2006. Serum 25-hydroxyvitamin D (25[OH]D) levels were drawn at admission. Patients with serum 25[OH]D levels < 20 ng/ml were considered to have inadequate levels and those with levels >20 ng/ml were considered to have adequate levels. Upon admission, opioid intake was documented and patients completed the Short Form-36 Health Status Questionnaire.

Results: The prevalence of vitamin D inadequacy was 26% (n=69/267). Among patients using opioids (n=140/267), 38 had inadequate vitamin D levels and 102 had adequate levels. The mean morphine equivalent dose for the inadequate vitamin D group was 133.5 mg/d compared to 70.0 mg/d for the adequate group (P=.001). The mean duration of opioid use for the inadequate and adequate vitamin D groups was 71.1 months and 43.8 months, respectively (P=.023). Opioid users with inadequate vitamin D levels reported worse physical functioning (P=.041) and health perception (P=.003) compared to opioid users with adequate levels.

Conclusion: To the authors' knowledge, this is the first reported prevalence of vitamin D inadequacy among patients seeking treatment for chronic pain of diverse etiologies. The prevalence and clinical correlates identified in this pilot study provide the basis for ascertain[ing] that vitamin D inadequacy may represent an under recognized source of nociception and impaired neuromuscular functioning among patients with chronic pain. Moreover, prospective trials are warranted to assess the effects of vitamin D repletion on pain outcomes and physiological measures of neuromuscular functioning among patients with chronic pain and comorbid vitamin D inadequacy.

Source: American Society of Anesthesiologists 2007 Anesthesiology 2007; vol 107: Abstract 1380 Annual Meeting in San Francisco, October 13-17. W. Michael Hooten, M.D., Michael K. Turner, M.D., John E. Schmidt, Ph.D Mayo Clinic College of Medicine, Rochester, Minnesota