Tuesday, March 3, 2009

Stroke of genius

I have discovered a real stroke of genius. If one says often enough and has enough money to put billboards up that a chiropractor caused a stroke, then it must be true. Madison Ave. discovered this years ago.

Here's a news piece about the billboards and the women who put them up.

(BTW there is no such word as chiropractry as used in the CBS news piece - they must have forgotten to use a spell-checker)

Surely if these billboards are up there must be some truth to it, no? Well if you asked me the question about a year ago I would have said, yes there does appear to be a risk of stroke after seeing a chiropractor. I have advocated that even though the odds were one in five hundred thousand treatments to one per five million treatments that one should still tell prospective patients about this small risk.

But then a huge study was published early last year.

Cassidy JD, Boyle E, Côté P, He Y, Hogg-Johnson S, Silver FL, et al . Risk of vertebrobasilar stroke and chiropractic care: results of a population-based case-control and case-crossover study. Spine. 2008;33(4 Suppl):S176-83.

Cassidy et al have found that the likelihood of having a stroke after seeing a chiropractor is the same as the likelihood of having a stroke after seeing an MD. Thus, the previous research that had found an association between chiropractic care and strokes were showing only half the picture because they didn't look at whether the association existed with other professionals. The problem isn't the intervention it is that one seeks care from a health professional. This is sort of how some advertisements work.

4 out of 5 ______ like this product. They don't tell you that 4 out of 5 are just as happy with the competitor's product. I've blogged on this before (see Katz and dogma) but I figure if repeating something that isn't true over and over will improve the odds that it will be believed maybe my stroke of genius is to repeat what is true.

It is critical to understand that association does not establish causation. If association did let us know what caused something then think about this. When one sees a photograph or video of a house fire in the news media one always sees fire engines. One might conclude that fire engines are there to cause the fire (as they are in Ray Bradbury's book Fahrenheit 451).
On the health front at one time research clearly showed the association between salt intake and hypertension. Eventually, it was discovered that salt intake isn't the culprit, it's fats and other elements of a poor diet. The reason salt looked as if it was the cause is because in the U.S. fatty foods tend to be salty, think french fries.

Well this stroke issue is looking similar to salt. The reason some people have strokes after seeing a chiropractor and a medical doctor is because they have the early symptoms of an event that may lead to a stroke and those symptoms send them to a doctor's office (be that a chiropractic or medical doctor).

In a way this is also similar to the issue of autism. Parents have what appears to be a normal child, the child gets immunized and then they notice abnormal behavior that turns out to be part of autism spectrum disorder. Did the immunization cause the autism. The best evidence says no but the parents searching for some reason for their child's behavior grasp at the immunization as the cause.

Similarly, the person who has a stroke grasps for a cause, and if they saw a chiropractor a malpractice attorney is often ready to say that the cause is the chiropractor.

Does this mean that chiropractic care is completely without any complications. Clearly any treatment that has the power to help has the power to hurt. It is just the best evidence right now doesn't support the association between cervical manipulation (usually done by chiropractors but now more and more PTs, MDs and DOs are doing this) and stroke.

What is really interesting about this whole campaign against chiropractic care is that the campaign isn't about cervical manipulation, which some PTs, MDs and DOs do it is about chiropractic cervical manipulation only. Granted DCs use spinal manipulation more than any other type of health professional and perform the vast majority of manipulative procedures, still why don't the people with the billboards and other media say cervical manipulation may cause a stroke instead of saying chiropractic might cause a stroke? This is another critical question because IF there was a problem with cervical manipulation is it only at the hands of a DC. There is one study that critics of chiropractic have often cited to show the risk of chiropractic care. This study from Germany purports to report on vertebral artery dissections after chiropractic care. Unfortunately for those who use this as evidence of chiropractic's harm only 11% of the subjects in this study were treated by chiropractors but 50% were treated by MDs and 14% by PTs. But to read the title or abstract alone one would be convinced that it is about care provided by chiropractors. Here's the citation (if you click on the link you can read the abstract):

Reuter U, Hamling M, Kavuk I, Einhaupl KM, Schielke E. Vertebral artery dissections after chiropractic neck manipulation in Germany over three years. J Neurol. 2006 Jun;253(6):724-30.

Again if the people who put up the billboard were concerned with public safety why put up billboards that say chiropractic rather than cervical manipulation?


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