A comparison of rheumatoid arthritis and fibromyalgia patients and healthycontrols exposed to a pulsed (200 mu T) magnetic field: effects on normal standing balance

Specific weak time varying pulsed magnetic fields (MF) have been shown to a lter animal and human behaviors, including pain perception and postural swa y. Here we demonstrate an objective assessment of exposure to pulsed MF's o n Rheumatoid Arthritis (RA) and Fibromyalgia (FM) patients and healthy cont rols using standing balance. 15 RA and 15 FM patients were recruited from a university hospital outpatient Rheumatology Clinic and 15 healthy controls from university students and personnel. Each subject stood on the center o f a 3-D forceplate to record postural sway within three square orthogonal c oil pairs (2 m, 1.75 m, 1.5 m) which generated a spatially uniform MF cente red at head level. Four 2-min exposure conditions (eyes open/eyes closed, s ham/MF) were applied in a random order. With eyes open and during sham expo sure, FM patients and controls appeared to have similar standing balance, w ith RA patients worse. With eyes closed, postural sway worsened for all thr ee groups, but more for RA and FM patients than controls. The Romberg Quoti ent (eyes closed/eyes open) was highest among FM patients. Mixed design ana lysis of variance on the center of pressure (COP) movements showed a signif icant interaction of eyes open/closed and sham/MF conditions [F = 8.78(1,42 ), P < 0.006]. Romberg Quotients of COP movements improved significantly wi th MF exposure [F = 9.5(1,42), P < 0.005] and COP path length showed an int eraction approaching significance with clinical diagnosis [F = 3.2(1,28), P < 0.09]. Therefore RA and FM patients, and healthy controls, have signific antly different postural sway in response to a specific pulsed MF. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.