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The power of placebo

Just when the silly season was starting to get on top of us, some welcome relief in the form of good solid science arrived on my desk. A study published in the BMJ looked at the therapeutic effect of wearing magnetic bracelets for pain control in osteoarthritis.¹

I must admit my personal bias here. When I was the team doctor for one of our professional football clubs, we used to be inundated with salesmen pushing their magnetic wares. Magnetic bandages, pillows, shoe inserts, wrist bands, knee bands, and who knows what else. It seems the only limitation in their product range was their own imagination. Their strategy of leaving piles of their products around the football club was in the hope that they could then claim endorsement by some gullible celebrity athlete who would pick up a free sample. Not surprisingly, the footballers loved them. The combination of a free sample and some hocus science was an absolute winner. In fact, the more magnetic things they had attached to their bodies the better. It is like the old adage regarding footballers—if someone came along with a pill for immortality, a footballer would take two of them.

You may well pooh-pooh this sales tactic but let me remind you that in 1999, the worldwide sales of magnetic products was estimated at $5 billion USD (£2.6 billion, 3.8 billion).²

So you can understand my obvious satisfaction when I read the study of magnetic bracelets.¹ In a prospective RCT of 194 subjects with osteoarthritis of the hip and knee, three groups were studied for their pain levels wearing a standard strength bipolar magnetic bracelet, a weak magnetic bracelet, and a dummy non-magnetic bracelet. After 12 weeks of wearing the bracelets, all three groups reported less pain and the two groups with the magnetic bracelets reported less pain than the placebo group (note that it is impossible to blind the subjects to their use of a non-magnetic bracelet given that it doesn’t stick to metal objects!) Despite this finding, there was no statistically significant difference in pain levels between the groups.

Previous studies in a variety of medical conditions have shown variable results from magnetic therapy with a few studies reporting a benefit in pain reduction^2,3 whereas larger most studies have reported no beneficial effect from magnetic therapy.^4–6

Interestingly the effect of the magnets on pain, although small, was similar to that seen with other traditional first line osteoarthritis treatments such as topical non-steroidal creams⁷ and exercise therapy.⁸ It is reassuring to know that in this era of evidence-based medicine that placebos still work.

REFERENCES

1. Harlow T, Greaves C, White A, et al. Randomized controlled trial of magnetic bracelets for relieving pain in osteoarthritis of the hip and knee. BMJ 2004;329:1450–4.[Abstract/Free Full Text]
2. Weintraub M. Magnetic biostimulation in painful diabetic peripheral neuropathy: a novel interventional randomized double blind double placebo cross over study. Am J Pain Management 1999;9:8–17.
3. Brown CS, Ling FW, Wan JY, et al. Efficacy of static magnetic field therapy on chronic pelvic pain: a double blind pilot study. Am J Obstet Gynecol 2002;187:1581–7.[CrossRef][Medline]
4. Collacott E, Zimmerman J, White P, et al. Bipolar permanent magnets for the treatment of chronic low back pain. JAMA 2000;283:1322–5.[Abstract/Free Full Text]
5. Caselli M, Clark N, Lazarus S, et al. Evaluation of magnetic foil and PPT insoles in the treatment of heel pain. J Am Podiatr Med Assoc 1997;87:11–6.[Abstract]
6. Winemiller M, Billow R, Lasowski E, et al. Effect of magnetic vs sham-magnetic insoles on plantar heel pain: a randomised controlled trial. JAMA 2003;290:45–56.
7. Bookman A, Williams K, Shainhouse J. Effect of a topical diclofenac solution for relieving symptoms of primary osteoarthritis of the knee: a randomized controlled trial. Can Med Assoc J 2004;171:333–8.[Abstract/Free Full Text]
8. O’Reilly S, Muir K, Doherty M. Effectiveness of home exercise on pain and disabilty form osteoarthritis of the knee: a randomized controlled trial. Ann Rheum Dis 1999;58:15–9.[Abstract/Free Full Text]

This Article Extract Full Text (PDF) Submit a response Read responses to this article Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this link to a friend Similar articles in this journal Similar articles in PubMed Add article to my folders Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by McCrory, P Search for Related Content PubMed PubMed Citation Articles by McCrory, P