The challenges of designing a placebo static magnet for double blind clinical trials

Active and placebo magnets

Clinical trials involving static magnets pose a difficult dilemma for researchers; how to “protect the blind”. That is, seeing you can’t hide a magnetic field, how do you prevent a patient from testing the magnet with, say a paper clip?

For studies like Vallbona it’s not such an issue, as subjects only wear the devices for 45 minutes and researchers can closely monitor subjects to make sure no one “cheats”.

However, many times you want to see the effects over days or even weeks and you can’t keep them under surveillance 24/7. Segal tried to counter this with a weak magnetic placebo, but the strength of the field entering the body was significant at 72 mT. So there is an argument that this was actually a dose-comparative study and not comparing with a true placebo. In addition, a research paper by Greaves & Harlow noted that…

Participants were however more likely to have an expectation of benefit (pain relief) with the higher strength magnetic bracelets.

We have attempted to solve this problem by using a very weak magnet at the top of the device and insulate it with iron. That way, most of the field is shielded from entering the body, but is still detectable from the top.

We call this passing the paper clip test. i.e. a paper clip still sticks to the outside of the magnet with negligible field entering the body.

In the photo, you can see the weak ferrous magnet at the top of the device before the lid was glued. It is surrounded by iron to insulate the field from penetrating into the body when worn. We also had to make a special black casing to prevent seeing what’s inside.

We have provided more information with detailed sketches on magnetic placebos.

If you are a researcher seeking to conduct clinical trials using static magnets, we have had experience in designing devices for a number of university sponsored trials. We would welcome your interest and can work with you to develop a suitable active and placebo device.

See the placebos in action here…

Main image: Active and placebo magnets almost ready for a clinical trial




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