Magnetic bracelets reduce pain in osteoarthritis of the hip and knee, finds a study in this week's Christmas issue of the BMJ.
Osteoarthritis affects around 760,000 people in the United Kingdom, producing over 3 million general practice consultations in 2000. Manufacturers of magnetic bracelets claim that they can reduce pain and worldwide sales were estimated at £2.6bn ($5bn) in 1999. But evidence about their effectiveness is contradictory.
Researchers from the Peninsula Medical School recruited 194 patients aged 45-80 years with osteoarthritis of the hip or knee from five rural general practices in Devon. Patients wore either a standard strength magnetic bracelet, a weak magnetic bracelet, or a non-magnetic (dummy) bracelet for 12 weeks. Changes in pain were recorded using a recognised pain scoring scale.
They found a significant reduction in pain scores between the standard and dummy magnet groups. The results for the weak magnet group were similar to those of the dummy magnets, and this suggests that the magnetic strength of the bracelet is important.
The authors emphasise that the benefits are in addition to existing treatments, which should not be suddenly stopped without discussion with their doctor. Also they note that high strength magnets (170mTesla or more) seem to be needed.
Although factors such as use of painkillers and patients' beliefs about the type of bracelet they were testing did not affect the results, the authors cannot be certain whether their findings are due to a specific effect of magnets or a placebo effect. But, whatever the mechanism, the benefit from magnetic bracelets seems clinically useful.
The (one-off) cost of bracelets (around £30-£50 or $58-$96), also compares well with that of painkillers, such as paracetamol and anti-inflammatory drugs, and larger investigations should now test the safety of magnets relative to the well-known risks of these drugs, they add.
Further work is also needed to replicate these findings and determine whether the effect extends beyond 12 weeks, they conclude.
Hannah Skeggs, Communications Department, Peninsula Medical School, Plymouth, UK
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