title: Vitamin D, race, and experimental pain sensitivity in older adults with knee osteoarthritis.
abstract: OBJECTIVE
  Low circulating serum levels of 25-hydroxyvitamin D (referred to hereafter as vitamin D) have been correlated with many health conditions, including chronic pain. Recent clinical practice guidelines define vitamin D levels <20 ng/ml as deficient and levels of 21-29 ng/ml as insufficient. Vitamin D insufficiency, including the most severe levels of deficiency, is more prevalent in black Americans. Ethnic and race group differences have been reported in both clinical and experimental pain, with black Americans reporting increased pain. The purpose of this study was to examine whether variations in vitamin D levels contribute to race differences in knee osteoarthritis pain.
  
  
  METHODS
  The sample consisted of 94 participants (74% women), including 45 blacks and 49 whites with symptomatic knee osteoarthritis. Their average age was 55.8 years (range 45-71 years). Participants completed a questionnaire on knee osteoarthritis symptoms and underwent quantitative sensory testing, including measures of sensitivity to heat-induced and mechanically induced pain.
  
  
  RESULTS
  Blacks had significantly lower levels of vitamin D compared to whites, demonstrated greater clinical pain, and showed greater sensitivity to heat-induced and mechanically induced pain. Low levels of vitamin D predicted increased experimental pain sensitivity, but did not predict self-reported clinical pain. Group differences in vitamin D levels significantly predicted group differences in heat pain and pressure pain thresholds at the index knee and ipsilateral forearm.
  
  
  CONCLUSIONS
  These data demonstrate that race differences in experimental pain are mediated by differences in the vitamin D level. Vitamin D deficiency may be a risk factor for increased knee osteoarthritis pain in black Americans.
authors.affiliation: University of Florida, Gainesville, FL 32610, USA. tglover@ufl.edu
authors.forename: T L
authors.initials: TL
authors.lastname: Glover
authors.forename: B R
authors.initials: BR
authors.lastname: Goodin
authors.forename: A L
authors.initials: AL
authors.lastname: Horgas
authors.forename: L L
authors.initials: LL
authors.lastname: Kindler
authors.forename: C D
authors.initials: CD
authors.lastname: King
authors.forename: K T
authors.initials: KT
authors.lastname: Sibille
authors.forename: C A
authors.initials: CA
authors.lastname: Peloquin
authors.forename: J L
authors.initials: JL
authors.lastname: Riley
authors.forename: R
authors.initials: R
authors.lastname: Staud
authors.forename: L A
authors.initials: LA
authors.lastname: Bradley
authors.forename: R B
authors.initials: RB
authors.lastname: Fillingim
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018771:Arthralgia / Q000208:ethnology / Q000503:physiopathology; D015415:Biomarkers / Q000097:blood; D044383:Black People / Q000208:ethnology*; D005260:Female; D006801:Humans; D006930:Hyperalgesia / Q000208:ethnology / Q000503:physiopathology; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000097:blood / Q000208:ethnology* / Q000503:physiopathology; D017288:Pain Threshold / Q000208:ethnology* / Q000502:physiology; D015995:Prevalence; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014807:Vitamin D / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications / Q000208:ethnology*; D044465:White People / Q000208:ethnology*; D001741:Black or African American
chemical_list: D015415:Biomarkers; D014807:Vitamin D