title: Exposure to a specific pulsed low-frequency magnetic field: a double-blind placebo-controlled study of effects on pain ratings in rheumatoid arthritis and fibromyalgia patients.
abstract: BACKGROUND
  Specific pulsed electromagnetic fields (PEMFs) have been shown to induce analgesia (antinociception) in snails, rodents and healthy human volunteers.
  
  
  OBJECTIVE
  The effect of specific PEMF exposure on pain and anxiety ratings was investigated in two patient populations.
  
  
  METHODS
  A double-blind, randomized, placebo-controlled parallel design was used.
  
  
  METHODS
  The present study investigated the effects of an acute 30 min magnetic field exposure (less than or equal to 400 microTpk; less than 3 kHz) on pain (McGill Pain Questionnaire [MPQ], visual analogue scale [VAS]) and anxiety (VAS) ratings in female rheumatoid arthritis (RA) (n=13; mean age 52 years) and fibromyalgia (FM) patients (n=18; mean age 51 years) who received either the PEMF or sham exposure treatment.
  
  
  RESULTS
  A repeated measures analysis revealed a significant pre-post-testing by condition interaction for the MPQ Pain Rating Index total for the RA patients, F(1,11)=5.09, P<0.05, estimate of effect size = 0.32, power = 0.54. A significant pre-post-effect for the same variable was present for the FM patients, F(1,15)=16.2, P<0.01, estimate of effect size = 0.52, power =0.96. Similar findings were found for MPQ subcomponents and the VAS (pain). There was no significant reduction in VAS anxiety ratings pre- to post-exposure for either the RA or FM patients.
  
  
  CONCLUSIONS
  These findings provide some initial support for the use of PEMF exposure in reducing pain in chronic pain populations and warrants continued investigation into the use of PEMF exposure for short-term pain relief.
authors.affiliation: Lawson Health Research Institute, St. Joseph's Health Care, London, Ontario N6A 4V2.
authors.forename: N M
authors.initials: NM
authors.lastname: Shupak
authors.forename: Julia C
authors.initials: JC
authors.lastname: McKay
authors.forename: Warren R
authors.initials: WR
authors.lastname: Nielson
authors.forename: Gary B
authors.initials: GB
authors.lastname: Rollman
authors.forename: Frank S
authors.initials: FS
authors.lastname: Prato
authors.forename: Alex W
authors.initials: AW
authors.lastname: Thomas
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001172:Arthritis, Rheumatoid / Q000628:therapy*; D004311:Double-Blind Method; D004574:Electromagnetic Fields; D005260:Female; D005356:Fibromyalgia / Q000628:therapy*; D006801:Humans; D008875:Middle Aged; D010147:Pain Measurement / Q000379:methods; D010555:Personality Inventory / Q000706:statistics & numerical data; D010919:Placebos; D011674:Pulse / Q000379:methods
chemical_list: D010919:Placebos