Detailed guides to painful problems, treatments & more

A point for PEMF? Pending confirmation of effect size

 •  • by Paul Ingraham
Get posts in your inbox:
Weekly nuggets of pain science news and insight, usually 100-300 words, with the occasional longer post. The blog is the “director’s commentary” on the core content of a library of major articles and books about common painful problems and popular treatments. See the blog archives or updates for the whole site.

Humans are always hoping for healing rays or waves of energy, and of course most of these things haven’t really worked out (e.g. TENS, lasers, infrared, ultrasound). Our hope is kept alive by flickers of genuine biological effects, but useful clinical efficacy is as elusive as a shy forest critter.

Pulsed electromagnetic field therapy (PEMF), like everything in this category, has shown some tantalizing promise here and there. But even if PEMF has some truly cool cellular effects, that’s no guarantee that we can have convenient, affordable, and effective PEMF emitters for a wide range of conditions. So “more study needed,” as always.

Photograph of an "ActiPatch" product box. It advertises (all caps) “DRUG-FREE, LONG-LASTING RELIEF” for “Back, Knee and Muscle & Joint.” There are 3 photos of the product in use, taped to a man’s back, knee, and shoulder blade. The box also advertises “Drug-Free. Safe for diabetics, arthritics, the elderly, and with any medications.”

An example of a consumer PEMF product, which are widely available. The ActiPatch® is quite cheap & advertised on like so right now: ‘PAIN RELIEF GUARANTEED!! It is SENSATION-FREE — no heat, no tingling, no odor! The only thing you will feel is RELIEF!’ Very classy pitch there. 🙄

A new study in the Archives of Physical Medicine and Rehabilitation reports that PEMF was “superior” to a sham for a common kind of shoulder pain, so-called “impingement” syndrome. (Actual impingement not necessarily included! But that’s another story. Whatever’s actually going on in there, these shoulders hurt and are hard to use.) This trial ticked all the gold-standard boxes: decent sample size (80), randomized, blinded twice, and controlled by the perfect sham.

PEMF is one of those treatments that is easy to test because you can compare it to a convincing fake: you just need a bogus device that doesn’t actually do anything, except maybe for a pulsing blue LED. In this case neither patients (single blind) nor researchers (double) could tell who was being bathed in genuine throbbing magnetic fields from a real PEMF-o-matic gadget. This really dampens the potential for misleading results.

And the results that Kandemir et al. report were that PEMF was “superior” to a fake. But is this true and meaningful, or only technically true? (Or any kind of true?) We don’t know how superior PEMF was, because the abstract in this new paper isn’t very chatty, and I don’t have the full text yet. That brevity could be hiding many sins. The authors don’t report how large the benefit of genuine PEMF was (the “effect size”). And who would hold that number back if it’s genuinely impressive?

Meme contrasting “the abstract” (a big lynx reaching out with one paw) with “the paper” (a cute widdle housecat in the same posture).

Almost every scientific paper. Sigh.

We’ll see when I get the full text. This is a little game I like to play, called “how much does the whole paper embarrass the abstract?” Anyone want to bet on whether that effect size was clinically significant? I’ll give it hundred to one odds, so it’s a big payday if you win!