Static magnetic field therapy for symptomatic diabetic neuropathy: a randomized, double-blind, placebo-controlled trial.
OBJECTIVE
To determine if constant wearing of multipolar, static magnetic (450G) shoe insoles can reduce neuropathic pain and quality of life (QOL) scores in symptomatic diabetic peripheral neuropathy (DPN).


DESIGN
Randomized, placebo-control, parallel study.


SETTING
Forty-eight centers in 27 states.


PARTICIPANTS
Three hundred seventy-five subjects with DPN stage II or III were randomly assigned to wear constantly magnetized insoles for 4 months; the placebo group wore similar, unmagnetized device.


INTERVENTION
Nerve conduction and/or quantified sensory testing were performed serially.


MAIN OUTCOME MEASURES
Daily visual analog scale scores for numbness or tingling and burning and QOL issues were tabulated over 4 months. Secondary measures included nerve conduction changes, role of placebo, and safety issues. Analysis of variance (ANOVA), analysis of covariance (ANCOVA), and chi-square analysis were performed.


RESULTS
There were statistically significant reductions during the third and fourth months in burning (mean change for magnet treatment, -12%; for sham, -3%; P<.05, ANCOVA), numbness and tingling (magnet, -10%; sham, +1%; P<.05, ANCOVA), and exercise-induced foot pain (magnet, -12%; sham, -4%; P<.05, ANCOVA). For a subset of patients with baseline severe pain, statistically significant reductions occurred from baseline through the fourth month in numbness and tingling (magnet, -32%; sham, -14%; P<.01, ANOVA) and foot pain (magnet, -41%; sham, -21%; P<.01, ANOVA).


CONCLUSIONS
Static magnetic fields can penetrate up to 20mm and appear to target the ectopic firing nociceptors in the epidermis and dermis. Analgesic benefits were achieved over time.