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Science, sometimes - stroke and chiropractic

Posted Apr 17 2010 4:00am
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The Connecticut Board of Chiropractic Examiners ruled on the issue of informed consent.  There was a hearing on a declaratory ruling regarding informed consent and stroke .  The board heard four days of testimony (which are available as videos at CT-N ).  Although the board's ruling hasn't yet hit the internet where I can find the exact text, it appears from newspaper reports that they ruled affirming that informed consent is the law in Connecticut but refused to require specific consent about a risk of stroke.  Both the New Haven Register and the Hartford Courant have weighed in on this issue and it appears that science isn't the strong suit for either newspaper.

Both papers believe that there is a risk of stroke from cervical manipulation.  Of course the two groups that advocated before the board for the ruling to require telling prospective chiropractic patients of the risk also believed there is a risk. To me what I have learned being part of this process is that science matters to many people only when it serves their interests. 

Nature of science

Science is an epistemological theory.  Epistemology is the study of how we acquire knowledge.  Science, as we know it, is just one method to acquire knowledge through what's called the scientific method.  Wikipedia's explanation of the scientific method is well done (at least today).  Simply, the method is to observe some phenomenon, create a hypothesis (i.e. a prediction) about that phenomenon, then test that hypothesis by controlled observation, an experiment. 

There are other epistemologies besides science.  For example divine revelation where knowledge comes from a deity. Some have called my profession, chiropractic a cult because there are some in the profession whose epistemology is based upon the work of a guru, typically BJ Palmer.  At one time most of medicine was based upon some guru's dogma.  For example anatomy was controlled by the works of Galen (1st - 2nd century of the common era) who really didn't have a clue what was in the human body - he'd looked at monkeys as human dissection wasn't allowed in his time. It wasn't until a skeptic Andreas Vesalius (16th century) applied the empirical method - noting that the bodies he dissected didn't look the way Galen said that anatomy progressed beyond the dogma of Galen.

One common epistemology is the use of anecdotes.  You know, "I once knew a guy who smoked a carton of cigarettes a day for 70 years and never got lung cancer.  So cigarettes are safe."  OK that's extreme but anecdotes have a tremendous hold upon our thinking and often it is very difficult to let science triumph when anecdote sits in contradiction of the science. Anecdotes which in health care publications are called case reports are very good at hypothesis generation, remember the scientific method is based upon an observation generating a hypothesis.  Case reports can help generate a hypothesis but never can validate the hypothesis.  I've heard it said often amongst skeptics of chiropractic that the pleural of anecdote is anecdotes not evidence.  I'll come back to this quote again!

Autism and Vaccinations

I know it looks like I'm completely switching gears but there is a logic to my digression.  As I have thought a lot about stroke and manipulation and autism and vaccinations I've come to see that they are analogous situations.  Think about this, a family has what appears to be a healthy normal baby.  They are in this blissful state of early parenthood enthralled with the baby who is developing a similar love for them.  Then suddenly the developing relationship on the babies side changes and the child becomes distant.  The parents seek advice and find that their now more withdrawn child appears to have autistic spectrum disorder.  To the parent this can be a devastating event. They want desperately to find a cure and if there isn't a cure (which there doesn't seem to be) they want to blame someone, something. This is only natural.  The parents feel as if someone, something has taken their child away from them.  Then they hear about a supposed link between autism and vaccinations.  Now they have people to blame.  They can blame the vaccine manufactures.  They can blame the government for trying to tell us that vaccines are safe. They can blame their doctors for giving their baby this poison which caused the problem.  To hear the anti-vaccination folks go on about autism and vaccines is to hear the voice of anger and vindictiveness.  They are not malicious people just untrained in the ways of science and prone to letting their emotions have greater sway over how they look at the evidence.

What about the evidence?  Those parents when confronted with the scientific evidence that does not support their belief that autism is caused by the vaccine, reject the evidence.  What is the basis for the rejection, valid critique of the science?  No, usually it is what comedian Stephen Colbert called truthinessTruthiness, which was the Merriam-Webster word of the year in 2006, is defined as: "Truth that comes from the gut, not books," and "The quality of preferring concepts or facts one wishes to be true, rather than concepts or facts known to be true."

Then a whole support industry develops around this belief.  There are organizations whose purpose is to advocate on behalf of the parents and spread the word that autism is definitively caused by vaccines.  This theory is advanced in such a way that reading the web one might believe it was the only one.

I was a participant in a webcast on vaccines for the California Department of Public Health titled " Wading through the Confusion ".  As one of my colleagues on the webcast, David G. Amaral, PhD, an autism researcher from the UC Davis M.I.N.D. Institute lamented is that there is inadequate research money available to find the cause of autism because the theory advocated by these groups has so dominated the discussion.
[Any one wishing to know more about this battle should read Paul Offit's book Autism’s False Prophets: Bad Science, Risky Medicine, and the Search for a Cure . The NYTimes article on Offit is enlightening about the lack of civility of public discourse on this issue.] 

Back to Stroke

Now think about ischemic strokes.  Isn't this what happens after a stroke in a younger person.  I mean we sort of think of stroke as a disorder that affects the elderly and it is.  The CDC lists death from stroke as the third most common cause of death behind heart attacks and cancer.  The rate of stroke increases dramatically as one ages. Stroke is a life changing event that affects not only the person who may be disabled, but the entire family and other caregivers as well. Utility analyses show that a major stroke is viewed by more than half of those at risk as being worse than death. (1)

So a younger person, say in their 40s - 50s has a ischemic stroke.  That person and their family are going have the same desire as the family who finds their child has developed autism, find someone to blame.  Well instead of a radicalized group of parents spreading the word that vaccines are the cause for autism there is a radicalized group of patients spreading the words that it must be a visit to a chiropractor. This theory that chiropractic cervical manipulation is the cause of strokes in the young has become so common that many MDs speak as if this is an established fact.  They don't really know what the research says about stroke but couple their distrust of chiropractic (2) which I think is a result of the AMA's illegal boycott(3) and it's easy to see how they would assume the connection between chiropractic care and stroke is valid.  Plus why search the literature to find this out, most people they know will tell them it is true.  It seems scientific evidence doesn't always matter.(4)

What is the epidemiology of these strokes?  They are rare representing 2% of all ischemic strokes but 10 to 25 percent of strokes in the young and middle aged.(5)  These facts are not well known so when someone in who is young or middle aged presents to a hospital with a stroke everyone wants to know why.   Given the bias and bad information then the question comes, "did you see a chiropractor within the past month?"  This only serves to expand the perceived value of this belief.  It is not uncommon to hear someone say that the risk is proven .  Proof is a word I tell my students that they can never use when referring to biomedical research.  There is either evidence that supports or refutes a particular hypothesis.  IF they want PROOF then their career choice should become mathematics not health care. 

Or that there is 80 years of science backing this up.  Well time to go back to that earlier quote: "the pleural of anecdote is anecdotes not evidence."    There isn't an 80 year history of science with respect to the association between cervical manipulation and stroke, there is an 80 year history of anecdotes that appears in the scientific literature.  The real science behind this issue has a much shorter history.  We get a survey of neurologists in 1995 (6) with a very poor response rate and which suffers from referral bias. (7)  Plus a survey doesn't establish cause and effect.  There are many studies of cases that have tried to discover the incidence.  For example this paper by Haldeman et al which estimated that one chiropractor in 48 would during the course of their practice career would be made aware of an arterial dissection following cervical manipulation.  But none of these papers actually evaluated the risk. 

There are only three studies that have evaluated the risk of stroke after manipulation.  And all three agree there is an association.  (9- 11)  The first two found a risk (9, 10) and the third (11) finding the same association provided evidence that explains the first two.  Cassidy et al (11) used the same data sources as Rothwell et al (9) but Cassidy et al study investigated one thing neither Smith (9) nor Rothwell (10) did and that is they determined the background rate of these strokes.  The issue is if the rate of strokes after chiropractic care was greater than the background rate (those that were occurring spontaneously not caused by the manipulation) then we would know what the added risk was due to manipulation. The finding, the rate of strokes in patients under 45 seeking care from their primary care physician was identical to the rate for those who had seen a chiropractor.  Thus seeking chiropractic care produced no extra risk for stroke over and above the background rate.  It appears that patients about to have a stroke from a dissection of a vertebral artery (the kind blamed on chiropractic for 80 years) seem to go to a doctor (a medical doctor or a chiropractic doctor) and the only reason the association between chiropractic and stroke appeared to be strong and not for PCPs is that no one asks the question in the emergency room, "did you see your MD within the past month?"

Some have complained that Cassidy et al was a "statistical study" (see this opinion piece or listen to Dr. Murray Katz 's testimony before the Connecticut Board of Chiropractic Examiners)  That's almost comical as a critique if not that it might ring true to people who don't understand biomedical research.  Those same critics never said that Rothwell (9) and Lee (10) were "statistical studies" which they are. 

In the publication BottomLine Health there is an article about stroke risk.  The author Dr. Steven Messe essentially dismisses cervical manipulation as a risk factor based upon Cassidy et al's work.(12) 

The nature of science is that what was known one day may change the next.  This isn't often comfortable to the average person but it is the way it is.As the late Prof. Natalia Romalis-Reytblatt (she was a math professor at UB and UB’s 2006-07 Professor of the Year) wrote
Mathematical results are either false or true (that is, proven or false) and nothing in between. Mathematics is one of the oldest fields of study and, probably, the only field whose findings are not reversed over time, only accumulated.
Math doesn't reverse it's findings but biomedical science does.  A few years ago I wrote about the risk of stroke from cervical manipulation.  But then the evidence changed.  So in the end this is an argument about looking at the science or ignoring the science and using emotion or choosing to use old science only.  To hear the science you can listen to Dr. David Cassidy testify before the board.  You can decide. 

SMP
  1. Goldstein LB, Adams R, Alberts MJ, Appel LJ, Brass LM, Bushnell CD, et al. Primary prevention of ischemic stroke: a guideline from the American Heart Association/American Stroke Association Stroke Council: cosponsored by the Atherosclerotic Peripheral Vascular Disease Interdisciplinary Working Group; Cardiovascular Nursing Council; Clinical Cardiology Council; Nutrition, Physical Activity, and Metabolism Council; and the Quality of Care and Outcomes Research Interdisciplinary Working Group: the American Academy of Neurology affirms the value of this guideline. Stroke. 2006 Jun;37(6):1583-633.  (this paper is available for free here )
  2. Busse JW, Jacobs C, Ngo T, Rodine R, Torrance D, Jim J, et al. Attitudes toward chiropractic: a survey of North American orthopedic surgeons. Spine (Phila Pa 1976). 2009 Dec 1;34(25):2818-25. ( Pubmed link )
  3. Getzendanner S. Permanent injunction order against AMA. Jama. 1988;259(1):81-2. ( Pubmed link )
  4. Gabbay J, le May A. Evidence based guidelines or collectively constructed "mindlines?" Ethnographic study of knowledge management in primary care. Bmj. 2004 Oct 30;329(7473):1013.(this paper is available for free here )
  5. Schievink WI. Spontaneous dissection of the carotid and vertebral arteries. N Engl J Med. 2001 Mar 22;344(12):898-906. ( Pubmed link )
  6. Lee KP, Carlini WG, McCormick GF, Albers GW. Neurologic complications following chiropractic manipulation: a survey of California neurologists. Neurology. 1995;45(6):1213-5. ( Pubmed link )
  7. Haldeman S, Carey P, Townsend M, Papadopoulos C. Clinical perceptions of the risk of vertebral artery dissection after cervical manipulation: the effect of referral bias. Spine J. 2002 Sep-Oct;2(5):334-42. ( Pubmed link )
  8. Haldeman S, Carey P, Townsend M, Papadopoulos C. Arterial dissections following cervical manipulation: the chiropractic experience. CMAJ. 2001 Oct 2;165(7):905-6. (this paper is available for free here )
  9. Rothwell DM, Bondy SJ, Williams JI. Chiropractic manipulation and stroke: a population-based case-control study. Stroke. 2001;32(5):1054-60. (this paper is available for free here )
  10. Smith WS, Johnston SC, Skalabrin EJ, Weaver M, Azari P, Albers GW, et al. Spinal manipulative therapy is an independent risk factor for vertebral artery dissection. Neurology. 2003 May 13;60(9):1424-8. ( Pubmed link )
  11. Cassidy JD, Boyle E, Cote 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 Feb 15;33(4 Suppl):S176-83. ( Pubmed link )
  12. Messe SR. Stroke Risk. BottomLine Health. 2010;24(3):1-2. 
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