Magnet therapy
Extraordinary claims, but no proved benefits
Magnetic devices that are claimed to be therapeutic include magnetic bracelets, insoles, wrist and knee bands, back and neck braces, and even pillows and mattresses. Their annual sales are estimated at $300m1 (£171m; {euro}252m) in the United States and more than a billion dollars globally.2 They have been advertised to cure a vast array of ills, particularly pain. A Google search for the terms "magnetic + healing" omitting "MRI resonance" yielded well over 20 000 pages, most of which tout healing by magnets. The reader is invited to insert "magnetic healing" into a web browser, and evaluate these spectacular claims.3
Many "controlled" experiments are suspect because it is difficult to blind subjects to the presence of a magnet. An example is a randomised trial of powerful magnetic bracelets for the relief of hip and knee osteoarthritis, which reports a significant decrease in pain because of the bracelets.4 The patients given real magnets could detect them because the magnets often stuck to keys in pockets. Perhaps subjects with magnetic bracelets subconsciously detected a tiny drag when the bracelets were near ferromagnetic surfaces (which are ubiquitous in modern life), and this distracted or otherwise influenced the perceived pain. Patients with fibromyalgia detected which sleeping pads were magnetic by their mechanical properties, by "comfort with the firmness"5 and thus unblinded the study.6 In a sophisticated postural assay, where magnetic soles were found to decrease swaying,7 the authors admit that the magnetic soles could have differed in stiffness from the controls. One of us suggested to a believer in magnetic healing that inexpensive refrigerator magnets were thin enough to be worn in dress shoes and would be equally "effective": she was delighted to find this was so (E Alvarez, private communication). We wonder if a cheap shoe insert would have had the same effect. In chronic pelvic pain a double blind study reported improvement owing to the continuous wearing of magnets, but admitted that blinding efficacy was compromised.8
For carpal tunnel syndrome pain, a double blind randomised study using magnet therapy9 ensured that magnets and shams were boxed individually so the treatments shouldn't be identified.10 There was no statistical difference between the magnet and sham, yet both showed an improvement. Hence future studies should include holders and bracelets that do not contain magnets. One of the commonly touted benefits of magnet therapy is relief of low back pain. However, despite a natural tendency to report positive results, a study of the effects of magnets found no effect.11
It is relevant to cost benefit ratios in clinical practice that magnets, which are claimed to be therapeutic, have caused financial harm.12 Money spent on expensive and unproved magnet therapy might be better spent on evidence based medicine. More importantly, self treatment with magnets may result in an underlying medical condition being left untreated.12 Sadly, some advertisers even claim that magnets are effective for cancer treatment and for increasing longevity; not surprisingly, these claims are unsupported by data.
Magnets are touted by successful athletes, allowed to be widely advertised, and sold without restrictions, so it is not surprising that lay people think that claims of therapeutic efficacy are reasonable. However—even theoretically—magnet therapy seems unrealistic.9 10 If human tissue were affected by magnets, one would expect the massive fields generated by magnetic resonance imaging (MRI) to have profound effects. Yet the much higher magnetic fields of MRI show neither ill13 nor healing10 effects.
Extraordinary claims demand extraordinary evidence. If there is any healing effect of magnets, it is apparently small since published research, both theoretical and experimental, is weighted heavily against any therapeutic benefit. Patients should be advised that magnet therapy has no proved benefits. If they insist on using a magnetic device they could be advised to buy the cheapest—this will at least alleviate the pain in their wallet.
Leonard Finegold, professor
Department of Physics, Drexel University, Philadelphia, PA 19014, USA
(L@drexel.edu)
Bruce L Flamm, clinical professor of obstetrics and gynaecology
Kaiser Permanente Medical Center, Riverside, CA 92505, USA
Competing interests: None declared.
References
1. Brody J. Less pain: is it in the magnets or in the mind? New York Times 2000;Nov 28: F9.
2. Weintraub M. Magnetic bio-stimulation in painful diabetic peripheral neuropathy: a novel intervention-a randomized, double-placebo crossover study. Am J Pain Manage 1999;9: 8-17.
3. Johnston L. Magnetic healing: What's the attraction?
www.healingtherapies.info/magnetic_healing.htm (accessed 21 Jul 2005).
4. Harlow T, Greaves C, White A, Brown L, Hart A, Ernst E. Randomised controlled trial of magnetic bracelets for relieving pain in osteoarthritis of the hip and knee. BMJ 2004;329: 1450-4.[Abstract/Free Full Text]
5. Colbert AP, Markov MS, Banerji M, Pill AA. Magnetic mattress pad use in patients with fibromyalgia: a randomized double-blind pilot study. J Back Musculoskeletal Rehab 1999;13: 19-31.[ISI]
6. Alfano AP, Taylor AG, Foresman PA, Dunkl PR, McConnell GG, Conaway MR, et al. Static magnetic fields for treatment of fibromyalgia: a randomized controlled trial. J Altern Complement Med 2001;7: 53-64.[ISI][Medline]
7. Suomi R, Koceja DM. Effect of magnetic insoles on postural sway measures in men and women during a static balance test. Percept Mot Skills 2001;92: 469-76.[CrossRef][ISI][Medline]
8. Brown CS, Ling FW, Wan JY, Pilla AA. Efficacy of static magnetic field therapy in chronic pelvic pain: a double-blind pilot study. Am J Obstet Gynecol 2002;187: 1581-7.[CrossRef][ISI][Medline]
9. Carter R, Aspy CB, Mold J. The effectiveness of magnet therapy for treatment of wrist pain attributed to carpal tunnel syndrome. J Fam Pract 2002;51: 38-40.[ISI][Medline]
10. Finegold L. Magnet therapy. Sci Rev Altern Med 1999;3: 26-33.
11. Collacott EA, Zimmerman JT, White DW, Rindone JP. Bipolar permanent magnets for the treatment of chronic low back pain: a pilot study. JAMA 2000;283: 1322-5.[Abstract/Free Full Text]
12. Livingston JD. Driving force: the natural history of magnets. Cambridge, Mass.: Harvard University Press, 1996.
13. Schenck JF. Safety of strong, static magnetic fields. J Magn Reson Imaging 2000;12: 2-19.[CrossRef][ISI][Medline]
