Therapeutic magnets or pulsed magnetic fields are offered in numerous forms, including magnetic jewelry, magnetic insoles, shoes, mattresses, wraps, and devices to provide pulsed magnetic fields. Magnets are variously advertised on websites and in printed advertisements to prevent, reduce, or relieve pain and stress, thereby warding off problems such as headaches, hypertension, gastritis, arrhythmias, depression, fatigue, arthritis flairs, and immune deficiencies. Pulsed magnetic fields also reportedly help by improving oxygenation of tissues, improving circulation, reducing pain (including acute pain, chronic pain, wound pain, pain from cramps, and pain from burns), slowing the aging process, and enhancing energy levels. One website describes a pulsed magnetic field device that will give the user more energy:
'Stiff and sore? With pulsed magnetic fields no more! Have you ever noticed that pain drains you of your energy? You won't believe how easy it is to lie down and regain energy and relief with the Magnopro. You don't have to work out, don't have to meditate, don't have to do yoga or all the things the practitioners have asked you to do. All you have to do is lie down while opening your mail, talking on the phone, reading or watching TV. You don't have to move your body. Yes, you can really have more energy without much effort using pulsed magnetic fields ...' .
These products are in many cases devices regulated by FDA, with specific oversight determined by the product design, claims, and perceived risks. However, they are often sold and advertised by firms that do not seek proper FDA review.
Several published studies describe clinical trials of magnets. The results of these studies, whether they show an effect or lack of effect for magnets, are typically contested by others. For example, a randomized, double-blind, placebo-controlled cross-over pilot study examined the effect of bipolar magnets on lower back pain . Nineteen men and women with stable lower back pain of duration 6 months and greater were eligible and participated in the study. Real (300 Gauss) and sham magnetic devices which were similar in appearance were applied to the patient's skin, covered with cloth, and then wrapped with a smooth gold-colored foil. Participants underwent 6 hour treatments three times per week for 2 weeks. They rated their pain on a visual analogue scale before and after each treatment. At the end of each week's treatment, subjects responded to the Pain Rating Index of the McGill Pain Questionnaire and were rated for range of motion in the lumbrosacral spine by a clinician. There were no statistically significant differences in any of the outcome measures between magnet and sham treatments. Others commenting on this study argue that the study was flawed because of sex bias (19 men, 1 woman), selection bias (disabled, retired, veterans), and that the intervention was weak because the subjects only wore the permanent static magnets (300 Gauss) 6 hours per day, 3 days per week, and the fact that the magnets may have slipped during the treatment . This simply emphasizes the difficulty of performing studies on alternative treatments: there may be no standards for treatments or methods for applying them, so that any negative finding may be construed as being due to inappropriate use of the treatment, rather than a generally ineffective treatment. That being said, a recent study of follow-up on outcomes for patients reporting to two general practices in Manchester with lower back pain indicated that 3 months after their first consultation, only 23% reported being free of lower back pain and disability . While bipolar permanent magnet treatment for persistent low back pain is of questionable value, allopathic treatment may not be much more effective in some cases. It may be worth examining whether unproven alternative devices or treatments are more likely to thrive when effective allopathic devices or treatments are lacking.
Another example of a condition with claims of treatment by magnets is diabetic neuropathy, a painful and disabling complication of high blood glucose, which is treated with drugs, including antidepressants, anticonvulsants, and analgesics, with mixed results. A small single-site pilot study of the effectiveness of magnetic foot insoles for the treatment of pain due to diabetic neuropathy reportedly showed a reduction in symptoms of burning and numbness and tingling . Consecutive patients (14) with diagnosed advanced chronic peripheral neuropathic pain secondary to diabetes, who had failed conventional pharmacologic treatments, and 10 patients with peripheral neuropathies not related to diabetes, were recruited for this study. These patients wore active (475 Gauss) or sham magnetic insoles on opposing feet (in shoes). They rated the level of pain on a continuous five-point visual analog scale twice daily for each foot. After 30 days, the active and sham insoles were switched and after the second month, all insoles were switched to active magnets. Nineteen of the 24 subjects finished the study - the other five withdrew for various reasons, including foot surgery, inability to 'tolerate application to their painful feet', and loss to follow-up. These patients were not included in the analysis, although arguably they should have been considered failures. In addition, not all the patients were randomized with respect to which side received the active magnet, as required by the protocol, and neither patients nor examiner were blinded as to which side had an active magnet. The authors report that 90% of the diabetic peripheral neuropathy patients had a statistically significant reduction in neuropathic pain compared to the non-diabetic neuropathy group. However, it is not clear what magnitude of pain change on a five-point scale would be significant clinically, neither is it clear that the comparison group is an appropriate control group. It is also unclear from the methods section whether participants were currently on medication for peripheral neuropathy - although the method section does state that there were no new pharmaco-logic interventions allowed during the study.
A more sophisticated clinical trial of magnetic field therapy for diabetic neuropathy, led by the same investigator, was performed at 48 centers in 27 states and enrolled 375 participants . While an improvement over the earlier study, this clinical trial also had certain weaknesses. In contrast to the preliminary study, patients were randomly assigned to the treatment or sham group. The report explicitly mentioned that patients were not to take any new analgesic drugs but could continue any medication for neuropathic pain that they already used. Patients wore a magnetized insole (450 Gauss) or a sham insole which looked similar. Participants rated their pain on an 11 point scale, three times daily for the 16 week period. They also rated their sleep (whether disturbed because of neuropathic pain) on a visual analogue scale and reduction of exercise-induced foot pain. The drop-out rates for the 199 member treatment group and the 176 member sham group were 23% and 25%, respectively. Foot pain scores decreased 31% for the treatment group and 25% for the sham group (baseline compared to month 4), a statistically significant decline.However, comparison of the mean ratings for groups suggests that clinically this was not a notable improvement (both groups had baseline pain ratings of 5.8 ± 2.3; at 4 months the active magnet group pain rating was 4.1 ± 2.7 and the sham group 4.3 ± 2.8). Sleep disturbance secondary to neuropathic pain also declined from the baseline in both magnet and sham groups, but this difference was not statistically significant. Note that treatment was not significantly different from placebo results.
An issue which repeatedly arises in these clinical studies is blinding patients and clinicians to the patient's treatment. Clinicians, study personnel, or study participants may check to see whether metal objects (such as paperclips) stick to the surface of the test device or whether the test device (such as an insole) sticks to the refrigerator door. In one study, there were efforts to improve blinding by arranging magnets in both the test and placebo device so that they emitted a comparable magnetic field on the external surface facing away from the treatment area, without exposing the treatment area to a magnetic field which exceeded background magnetic field in the placebo device . This study was designed to test the feasibility of studying static magnetic therapy for treatment of osteoarthritis pain and to assess whether the sham device design was effective at concealing the group assignment from patients. Twenty-six patients were randomly
ADVERSE EVENTS ASSOCIATED WITH ALTERNATIVE OR COMPLEMENTARY DEVICES
assigned to the active magnet or placebo group. Thirteen patients received active magnets (maximum 100 Gauss/mm) sewn into a knee sleeve and the placebo group received the placebo knee sleeve. The groups were comparable on baseline patient characteristics, except for the Kellgren/Lawrence X-ray grade, a scale to measure the degree of osteoarthritis, with patients with placebo magnets having had significantly lower grades than those in the active treatment group. Patients were encouraged not to use their usual analgesic medications for several days prior to starting the treatment or were given acetaminophen but asked not to take it for 48 hours prior to each visit (although non-compliance with this did not disqualify participants from the study). Patients were asked to wear their knee sleeve for 6 hours per day. Pain was assessed at baseline, 4 hours, 1 week, and 6 weeks after the start of the trial. Patients responded to the five-item pain subscale from the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index and demonstrated their pain on a visual analogue scale.
After 4 hours of treatment, patients with active magnets reported a small but statistically significant change in pain compared to the placebo group. However, at the 1 and 6 week follow-ups, there was no difference between pain reportedby the active magnet and the sham placebo treatment groups. Concern over the participants discovering their treatment group was borne out by the finding that 69% of the active magnet group and 46% of the placebo group admitted to either intentionally testing for, or inadvertently observing, their device's magnetic properties.
In this study , as in others [27,31], there are reductions in pain ratings for both active treatment and sham control groups overtime. A meta-analysis of 130 clinical trials that compare a placebo to no treatment  indicates that placebo is not an effective treatment when binary outcomes are used but shows some effectiveness when continuous outcomes are used, particularly for subjective outcomes, such as pain relief. The placebo effect was diminished by larger sample size in this study. This is of interest, since in most of the clinical trials cited above, the placebo/sham treatment was virtually as effective as the active treatment. This study re-emphasizes the importance of successful blinding, adequate sample size, and appropriate outcome measures for an honest evaluation of the effectiveness of complementary or alternative devices.
It is notable that studies for effectiveness for magnets are typically for medical issues that involve pain for which conventional medicine does not provide an adequate solution: diabetic neuropathy [30,31], chronic back pain , plantar heel pain , and fibromyalgia , to name a few. These ailments are notoriously resistant to successful treatment.
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