Evidence Repels Concept of Magnetic Pain Relief

EXETER, England, Sept. 24 -- Although millions are attracted to the notion that magnets relieve or prevent aches and pains, the preponderance of evidence holds otherwise, found researchers here.
A meta-analysis of the clinical data showed no significant improvement in pain for people who wore magnets, according to Max Pittler M.D. Ph.D., and colleagues at the Peninsula Medical School of the Universities of Exeter and Plymouth here.
The exception might be peripheral joint osteoarthritis, in which three out of four trials reported a benefit, Dr. Pittler and colleagues reported in the Sept. 25 issue of the Canadian Medical Association Journal.
"Peripheral joint osteoarthritis was the one condition for which the evidence appeared encouraging," the researchers said. "For all other conditions, there was no convincing evidence to suggest that static magnets might be effective for pain relief."
Static magnets sold for pain relief are a multi-billion industry, Dr. Pittler and colleagues noted, despite an absence of clear evidence that they work. Magnets sold for this purpose generally have a strength of between 30 and 500 microTesla, small compared with the 1.5 to 3 Tesla used in magnetic resonance imaging machines.
The researchers found 29 potentially relevant studies in a literature search but threw out four of them because they had only been published as abstracts or compared strong magnetic fields. The researchers excluded another nine trials from the systematic review because there was insufficient data to permit statistical pooling.
Of the remaining 16 trials, the researchers were able to conduct a meta-analysis on nine randomized controlled trials because they all measured pain using a standard 100-mm visual analog scale.
The nine studies looked at foot pain, fibromyalgia, lower back pain, carpal tunnel syndrome, diabetic peripheral neuropathy, osteoarthritis and delayed onset muscle soreness.
The meta-analysis showed that, overall, the effect of magnets was not significant, the researchers said. On the visual analog scale, the weighted mean difference between the magnet arm and placebo was 2.1 mm, with a 95% confidence interval from minus 1.8 to 5.9. The P value was 0.29.
The sole spot of hope for the magnetically inclined was osteoarthritis, the researchers said, which was assessed in four double-blind randomized controlled trials, with a total sample size of 275.
Two small trials (with 26 and 43 participants) reported some positive effects of static magnets - worn for various periods of time -- compared with placebo and weak magnets. A larger trial, with 193 participants had similar results compared with placebo.
On the other hand, a small study of 13 people who had continuous magnet treatment for a 24-hour period for their knee osteoarthritis saw no effect, the researchers said.
The studies were difficult to compare directly because their design varied widely.
In other words, there's not enough evidence "to exclude a clinically important benefit, which creates an opportunity for further investigation," Dr. Pittler and colleagues concluded.
The researchers reported they had no competing interests. They did not report funding sources for the study. Primary source: Canadian Medical Association JournalSource reference: Pittler MH et al. "Static magnets for reducing pain: systematic review and meta-analysis of randomized trials." CMAJ 2007;177(7):736-42.