Lets be clear about stroke injury

Lets be clear about stroke injury

Having been adjusted since birth, having adjusted my children and hundreds of other children since birth, I find it hard to remember that people, who have never experienced chiropractic, have concerns regarding its safety.

For example, someone maybe reluctant to try chiropractic because they believe chiropractic adjustments could cause a stroke. Did you know that there has never actually been ANY scientifically valid data to show that chiropractic care causes stroke!

How is it possible then that we hear about people suffering strokes and the story is linked to chiropractic?
Well, misleading reporting in medical literature regarding chiropractic has been widespread over the last few decades.  The terms chiropractic and chiropractor have been misused in many medical journal articles that examine the safety of chiropractic. Terret (1994) discusses how authors have frequently quoted examples of  “chiropractic”  injury when it is clearly known that the involved therapist was not a chiropractor.1 Some of the examples border on the absurd. For instance, the Australian Medical Association (AMA) published a document discussing complications of chiropractic manipulation, yet when the references and original reports were examined carefully, the “chiropractors”  referred to included among others, a blind, unlicensed masseur at a local health club and a barber in India.2

One of the world’s leading experts in study design has explained why valid data on this topic is impossible to find – The association between stroke and chiropractic is simply so small and so rare it would take a study of tens of millions of patients to even attempt to determine a direct link.3Obviously no study like this has ever been done.

So what data has been found? The majority of studies undertaken and reported in the media have looked for associations between chiropractic and VBA (vertebrobasiliar)stroke. Associations are very different to cause, yet often the two get confused (for instance, the association between ambulances and injured people does not mean that ambulances cause the injuries!) Some of the most publicised studies look for an association by asking VBA stroke patients if they visited a chiropractor a week or thirty days prior to their stroke. The incidence of an association between the two has been shown to be extremely rare. In the actual population, the number of people who went to a chiropractor and never had a stroke is vast, as is the proportion of people who never went to a chiropractor and had a stroke. This overall perspective is not conveyed by these studies, which creates a picture that is misleading and incomplete.

By using a parallel example Chestnut (2004) highlights the frequently faulty logic of the research.4 Instead of questioning stroke patients, imagine you asked a group of cancer remission patients if they had been to see a chiropractor in the last 30 days, and a proportion of 2% said that Yes, they had had an appointment with a chiropractor. Would it be logical to conclude that chiropractic caused the cancer remission? Would it be prudent for all medical practitioners to promote this association as a cure for cancer? Would you forget about questioning why and how the other 98% of patients who never saw the chiropractor nonetheless had cancer remission? Based on any understanding of probability, causes, scientific methods, logic, and ethics, it is clear that the data is grossly incomplete and that any implication that chiropractic cures cancer would be very misleading indeed.

Fortunately not all studies make such dramatic errors even if they do have their limitations. Cassidy et al (2008) recently looked for an association between chiropractic visits and VBA stroke and an association between GP visits and VBA stroke.5 They compared the two and found no difference  – patients having spinal manipulation did not have a greater rate of stroke than patients having primary medical care with a GP. Again, it could not be demonstrated that seeing a chiropractor or a GP had anything to do with causing stroke. Instead (as the study concluded) the main reason for any association was most likely due to patients seeking care for neck pain and headache before their stroke, since these are very common precursory symptoms.6 The study also noted that the type of stroke in question is such a rare event in the population, that between 1993 and 2002 in Ontario, there were only 818 stroke hospitalizations in a population of more than 100 million persons!7 So, not only is it extremely rare to have one of these strokes in general terms,  it is so rare to have one associated with chiropractic care that the risk can´t even be accurately determined.

Common medical treatments for neck pain and headache such as anti-inflamatories have medically acceptable risk ratios that far exceed even the highest risk estimates for chiropractic 8. In light of this, it is interesting that so much attention gets focused on an association that is so remarkably small.
So if the association between chiropractic and stroke is so small, what is VBA stroke most commonly associated with?

The answer might surprise you but it is well documented in the literature. The majority of VBA strokes are classified as spontaneous (no triggering activity identified) followed by classifications of ‘‘trivial trauma’’ or ‘‘mundane common activities of daily living,’’ such as walking, kneeling to pray, and household chores. Other implicated activities include motor vehicle collisions, shoulder checking while driving, sports, lifting, working overhead, falls, sneezing, and coughing 9.

Two things are important to consider here. Firstly, all stroke patients will be exposed to mundane common activities of daily living.  In other words, there is no stroke patient in history that has avoided being exposed to the most commonly reported activities that hypothetically trigger stroke. Considering that you could never isolate out all these daily activities such as driving, walking, and sneezing, how could it ever be plausible that for a stroke patient who saw a chiropractor 30 days prior, the cause of the stroke was solely due to chiropractic? Secondly, research has looked at how much force is transmitted to the vertebral artery during a chiropractic adjustment and an adjustment represents less force to the vertebral artery than turning the head within its´ normal range of movement!10

In other words, chiropractic adjustments have been shown to be gentler on the vertebral arteries than common activities of daily living!

In summary, Chestnut (2004) outlines these facts with great simplicity11:

  • In the medical literature the vast majority of VBA stroke have no relation to chiropractic
  • Literally millions of chiropractic adjustments are performed every year without incidence of VBA stroke
  • No valid data exists to show what caused any VBA stroke
  • The majority of activities identified as triggering stroke are classified as ´´spontaneous´´ or ´´trivial trauma´´ such as household chores or walking
  • The forces on the vertebral artery during a chiropractic adjustment have been shown to be less than the force of a person turning their head
  • Every stroke patient has been recently exposed to mundane common activities of daily living identified as commonly precipitating VBA stroke
  • The association between VBA stroke and chiropractic is so small that studies are unable to determine the risk.
  • The most common medical treatments for neck pain such as anti-inflammatories have medically acceptable risk ratios that are far higher than any risk hypothesized with chiropractic care.

Chiropractic has had a remarkable safety record for over 100 years. When the data from the literature is examined carefully it is obvious that Chiropractic is a safe and effective approach to health.



(1),(2),:Terret AG. Misuse of the Literature by Medical Authors in Discussing Spinal Manipulative Therapy Injury. J Manipulative Physiol Ther.1995; 18(4): 203-210.
(3)(4),(8),(11):Chestnut J. The Stroke Issue: Paucity of Valid Data, Plethora of Unsubstantiated Conjecture. J Manipulative Physiol Ther. 2004; 27: 368-372
(5),(6),(7)(9):Cassidy JD, Boyle E, Cote P, He Y, Hogg-Johnson S, Silver FL, Bondy SJ. Risk of Vertebrobasiliar Stroke and Chiropractic Care. Eur Spine J. 2008; 17(1):176-183
(10) Symons BP, Leonard T, Herzog W. Internal Forces Sustained by the Vertebral Artery During Spinal Manipulative Therapy. J Manipulative Physiol Ther. 2002; 25(8):504-510.