Few subjects lead to such heated debate as the risk of stroke after chiropractic manipulations (if you think this is an exaggeration, look at the comment sections of previous posts on this subject). Almost invariably, one comes to the conclusion that more evidence would be helpful for arriving at firmer conclusions. Before this background, this new publication by researchers (mostly chiropractors) from the US ‘Dartmouth Institute for Health Policy & Clinical Practice’ is noteworthy.

The purpose of this study was to quantify the risk of stroke after chiropractic spinal manipulation, as compared to evaluation by a primary care physician, for Medicare beneficiaries aged 66 to 99 years with neck pain.

The researchers conducted a retrospective cohort analysis of a 100% sample of annualized Medicare claims data on 1 157 475 beneficiaries aged 66 to 99 years with an office visit to either a chiropractor or to a primary care physician for neck pain. They compared hazard of vertebrobasilar stroke and any stroke at 7 and 30 days after office visit using a Cox proportional hazards model. We used direct adjusted survival curves to estimate cumulative probability of stroke up to 30 days for the 2 cohorts.

The findings indicate that the proportion of subjects with a stroke of any type in the chiropractic cohort was 1.2 per 1000 at 7 days and 5.1 per 1000 at 30 days. In the primary care cohort, the proportion of subjects with a stroke of any type was 1.4 per 1000 at 7 days and 2.8 per 1000 at 30 days. In the chiropractic cohort, the adjusted risk of stroke was significantly lower at 7 days as compared to the primary care cohort (hazard ratio, 0.39; 95% confidence interval, 0.33-0.45), but at 30 days, a slight elevation in risk was observed for the chiropractic cohort (hazard ratio, 1.10; 95% confidence interval, 1.01-1.19).

The authors conclude that, among Medicare B beneficiaries aged 66 to 99 years with neck pain, incidence of vertebrobasilar stroke was extremely low. Small differences in risk between patients who saw a chiropractor and those who saw a primary care physician are probably not clinically significant.

I do, of course, applaud any new evidence on this rather ‘hot’ topic – but is it just me, or are the above conclusions a bit odd? Five strokes per 1000 patients is definitely not “extremely low” in my book; and furthermore I do wonder whether all experts would agree that a doubling of risk at 30 days in the chiropractic cohort is “probably not clinically significant” – particularly, if we consider that chiropractic spinal manipulation has so very little proven benefit.


29 Responses to New data on the risk of stroke due to chiropractic spinal manipulation

  • tye fact is that visiting a physician appears to involve more risk than a chiropractor. That’s extra fly what the study shows and this study along with most others shows some association between visiting physicians in general and the incident of stroke. At 7 days follow up the risk of associaon with DC visits is LESS than going to see a physician. At 30 days it is marginally more. BUT, given the simple logic that if neck manipulation were ‘causing’ stroke one would sensibly think that this would happen EARLIER ……NOT LATER. So these results in any other balanced judgement would be further evidence of lack of causation of neck manipulation for stroke. Excellent news…….and corroborates most of the important and well conducted studies in this area which say the same thing. The evidence is stacking up against your rather one dimensional argument in this area E. You are increaingly in a minority in feeling the evidence says anything other than LACK OF CAUSATION.

    • is wishful thinking endemic in Bournemouth?

    • what the results do imply is:
      1) after 7 days there is no excess risk
      2) after 30 days there may be an excess risk (it is conceivable that stokes occur late after an arterial injury, or the diagnosis is delayed by more than 7 days).
      the studies do NOT all “say the same thing”. consider that this analysis is confined to the elderly!!!

    • @Dave Newell

      tye fact is that visiting a physician appears to involve more risk than a chiropractor.

      You are 180° off course there. The risk associated with chiropractic is significantly higher in the chiro-arm than the PCP arm. That calls for explanation. The 7- day estimate is likely to be affected by unsubstantiated exclusions of patients presenting same day with stroke and patients seeking PCP as well as chiropractic during the observation period. The risk may also be significantly underestimated in this study. See my comment below.

      PS: The link to your posted website is broken.

  • That should read ‘ The fact is……..’ and ‘ that’s exactly what the study…….’

    Apologies for the spelling……

  • Woah! Why no one younger than 66?

  • To me, this is a troubling paper for several reasons.
    I find the study wanting in many respects and the conclusion insufficient and misleading.

    The (convenience) cohort of Medicare patients 66+ yo is a difficult one because in this cohort, stroke incidence from any cause is significant. For a specific cause risk signal to get clearly through the noise of any other causes, this signal will have to be rather strong.
    Also, it is an ill chosen sample for this extremely important suspicion of an infrequent but extremely serious, totally preventable[sic] public health hazard, as there are indications that the main risk effect of chiropractic related stroke is in the young and healthy age group below thirty-ish if I am not mistaken.
    The chiropractic arm of this very large, retrospective study was significantly younger and healthier as is reported and discussed (plus points for that, at least). All-cause stroke frequency is known to increase significantly with age.
    Nevertheless, there is a significant difference in 30-day stroke risk between the groups with a 0.515% icnidence in the chiro-arm vs. 0.277% in the PCP arm giving an excess observed number of 600 strokes in the younger and healthier chiropractic group!!! That’s a lot of people, especially if, as I suspect it is in the part with better health, more active and better overall QOL who frequent the chiropractic parlours.
    Or, if we consider the PCP group as a control without a visit-associated exposure to stroke inducing risk, the excess number of chiropractic associated strokes in the total study population was 2704 or 2.4 per 1000 elderly, active people.
    I would tend to call that a clinically significant number as well.
    Why is this not discussed in the paper as a loud cry for a more thorough search for causality, which is already suspected??
    Further, I suspect the risk associated with chiropractic visits in this study may be significantly underestimated.

    For analysis of hazard of stroke within 30 days, we excluded subjects who were hospitalized for stroke on the same day as the office visit because these patients likely presented with signs or symptoms of stroke (Fig 2)

    So the authors arbitrarily annulled 55 chiropractic visits who were hospitalised for stroke on the day of the visit, without any mention of a preceding same day intervention! The 278 out of 1089 stroke patients who saw their PCP on the day of hospitalisation (25.53% of the stroke patients) very probably were diagnosed correctly at the first visit and sent to hospital (without wringing their neck first, mind you). Omitting these cases seriously biases the
    The authors also ignore the possibility of repeat interventions as an independent risk factor by annulling every visit not leading to a stroke before the repeat visit and set the new visit as the index date.
    What is there to say that the 9,6 repeat visits (average) for neck pain to a chiropractor, presumably each visit associated with an intervention, is not the real reason for the excess 600 (at least) strokes in that group?
    The average number of visits to the PCP was only 1.58, a figure one might have expected
    My chiropractor, who is US-schooled had me come twice a week for a while and then weekly (until I relised my wallet was being was being “Hoowered” without me getting any better). There is nothing to say that the 55 same-day chiro-group strokes censored out were not a repeat visit for worsening symptoms from a recent “adjustment”. Or that the damaging intervention was not earlier in that same day or even coincident with the stroke?

    …38 138 (3%) had seen both types of providers: we excluded these subjects from the study population, thus creating 2 mutually exclusive cohorts of chiropractic and primary care patients.

    This exclusion may hide cases with chiropractic associated stroke and subsequently went to see their PCP.
    I could go on but I have better things to do just now…
    I submit this comment as is, with a humble reservation for errors as I went through this in a bit of a hurry and have not thoroughly double checked calculations, reasoning or typing. Any substantiated corrections are of course welcome
    Have a nice saturday evening.

    • Bjorn…If there really were a substantial risk then strokes would be at epidemic proportions and the association would be clearly demonstrable. Why then this is not the case? No matter how one nits and picks at everything that emerges that suggest the association is probably not causative ( and there Is substantive and consistant evidence that supports this interpretation) the fact of the matter is that risks, if at all present are very very low. Given that harm/ benefit of NSAIDS is likely to be substantially higher, then manipualtion should, given judicious and skilled use and a highly cautious approach when suspicious symptamotology presents, be considered a potential intervention for the consenting and clinically appropriate patient. For those not wanting this, and/or at some additional risk of adverse events then mobilisation may also be appropriate. Medicine operates like this EVERY DAY, and sometimes at the edge of far far thinner risk/cost/benefit fractions. Manipulation, as with many other effective interventions for MSK pain must be placed in the round context of all potential treatments and the culture within which we see them as acceptable or otherwise. Otherwise it seems, and becomes patently clear here on some of these blogs, that these disussions descend into nothing more than a witch hunters rhetoric.

      • @David Newell
        What do you mean by “substantial risk”??
        The risk ratio is numerically small, everyone agrees on that. but in relation to risk-benefit and risk consequences it is enourmous. The risk is b£@@dy well substantial and real to the people who died and suffered from stroke after being manipulated to the neck. A large part of them were young and healthy and thus missed out on a large part of their lifetime. Thats what I (we) call substantial.
        There may definitely be an unknown hidden number of neck “adjustment” related (note I did not say “caused”)VBA strokes. A traumatic VBA dissection will not always develop full symptoms right away. The distribution of such delay is of course unknown but a build up of thrombus takes time and may dislodge later in the day or even many days or even weeks later. A person found dead in her bed or brought unconscious to hospital and spending the rest of her life as a vegetable will not readily report that she was at the chiropractors parlour being manipulated that morning.
        The guns are smoking and the barrels feel hot.
        NSAID’s happen to be protective against this clot build-up via their anticoagulant effect. So if the person was smart[sic] enough to take diclofenac for the neck symptoms, it might actually save her from clot build-up. The thrombogenic effect discussed in the article is another and more long-term, CVD associated effect and constitutes a doubtful mechanism of the highly speculative (their words) PCP-visit-related stroke risk.
        The data are here in table 2 for anyone to use. You only need the first three rows. The mathematics are very simple. The full text of the article is there too, free for all.
        The risk ratio very clearly shows that overall, the risk of stroke is definitely higher in the chiro group for the observation period. If you know how to, you can do a simple chi-square calculation on the 2×2 data for stroke incidence in the cohorts to see that the difference is of course ridiculously significant in this large dataset.
        That the authors jump through several hoops to make it appear like the risk is less in the chiro group, the total figures are there and demand an explanation.
        To me there is all too much cherry-picking and hoop jumping in the setup of this study.
        There is a lot more peculiarities in this article. One is that overall mortality is higher in the chiro cohort, 9.65 vs. 9.1, albeit not significant difference, it should be the other way around as the chiro patients were both younger and healthier as stated in the article. This may be pure chance but…??
        Now that I come back to the matter, I saw immediately a small-ish error I made regarding proportions :/
        It does not alter in any way the reasoning or the conclusion about the evidently higher stroke risk in the chiro group. But it shows you should always give yourself time for projects like this, and lay aside the text for a while before coming back to it and reviewing at least one more time before submitting.
        Kudos to those who catch this rather puny error 🙂

  • Ps..Bjorn…..yes you are indeed mistaken..there is no increased risk over and above that of visiting a medical physician for risk of stroke in those under 45. None whatsoever. NONE. See Cassidys case/ control and far more water tight, case/ cross over study.

  • Bjorn. Don’t even try to suggest that taking nasaids for neck pain is safer than neck manipulation. Nasaids may be anticoagulative, but for many that are corrosive to the stomach, and responsible for quite a number of heart attacks.

    It doesn’t appear to me that any future study would satisfy you (or edzard) that cervical spine mobs/manips have a low incidence of serious injury.

    And show some respect on you’re responses to David Newell. He is well respected in the field of chiro, Osteo, and Physio. He’s working hard to bring reform into the Chiro profession and should acknowledged for that. Both You’res and Edzards responses above are just plainly abrasive and smell a bit bigoted.

    You both expect respect, but both give none.

    • much of alternative medicine seems to suffer from a chronic condition which entails confusing criticism with disrespect.

      • I suspect there will be a homeopathic remedy for that. There always is.

      • A typical patronising response as expected from you ed.

        • thank you for proving my point

        • And followed up perfectly by you Alan.

          You need to watch the film “Django”. You two remind me of two characters in that film.

          • An interesting short article from Paul Ingraham on tone troll’s. I thought it related to this nicely.

          • Yeah yeah Paul…guilty as charged. 🙂

            There are plenty of “tone trolls” on this blog, including the owner(come on edzard…put your hand up:)….).

            In this instance, I didn’t mean it as a troll comment. I just finished watching the film “Django” and the comment from Alan’s after Edzards just reminded me of a scene in the film and it made me laugh…For those that have seen it it’s the part where Samuel J is standing behind Leo decap at the dinner table and he’s echoing everything Leo is saying….I guess you had to be there. Anyway. I’ll do my best not to “tone troll” anymore. 🙁

            Ps. As for the mathematical question that I need to answer before sending my post…it seems to be getting harder. This time I had to answer what 9 x 9 equals. Nearly had to use a calculator! Is this a conspiracy thing or something?(sorry…tone troll…couldn’t help myself. :)….)

    • @ David sparavec

      Respect is a mutual necessity. The perception of respect is always modulated by the recipients subjectivity.
      I have chosen not to hide my earnest opinion of what I sincerely regard as make-believe healthcare.
      Count of publications or use of scientific language is not a measure of scholarly proficiency any more. It is respect for evidence and the strength and integrity of one’s scientific substantiation that counts towards deserving professional respect.
      I do not doubt that you and Mr. Newell and most all chiropractors are fine, honest and respect-deserving human beings. My criticism is not “ad hominem” it is “ad disciplinam”. If my words are perceived as personally abrasive or hurting, the “ad hominem” is a subjective projection.

      A genuine scholar, when his work is criticised, does not resort to unsubstantiated, impulsive declarations.
      I have, admittedly accompanied by sentiments, put forth points of criticism against the methodology and conclusions of the paper in question and I consider myself having substantiated the arguments so they may be met with reason and substance. If someone manages to take down these arguments with reasonable and credible arguments, I will welcome this and I promise even, if warranted, to change my mind about chiropractic, which is at the moment based on my own experience and weighing of all evidence I have encountered.

      Once again:
      Of course the incidence of chiropractic injury can be described with the word “low” in a numerical sense. No one refutes this fact. But the dire consequences and the absence of demonstrated efficacy of the suspected intervention makes the description “low incidence but very substantial risk” more than adequate.
      What is more, it is preventable!
      If the chiropractic community showed more respect for the “smoking guns and warm barrels” I would probably dress my words in prettier, less abrasive costumes.

      • I accept your position on my comments Bjorn.

        I’m still somewhat surprised that you do feel that NASAiDs are more appropriate and safer than cervical spine mobs/manips for non specific mechanical neck pain.

        • you don’t get it, do you?
          they have a better risk/benefit profile because they actually have an effect !!!

          • Edzard. I do do get it. The studies you refer to suggest that nasaids are just as effective as spinal mobs/manips. But the risk of something “going wrong” and causing death or at the very least some serious complication are much higher with nasaids. Don’t get me wrong edzard, I do prescribe nasaids to patients who are undergoing treatment by myself for various back and neck pain, as I feel (and the studies support this), that the patient is much better off embarking in self managed strategies rather that continuing passive care. But to suggest that these meds are the only thing that a particular patient with back or neck pain needs is just not realistic in the clinical world that the DC/DO/Physio lives in. Most of the patients that enter our clinics are already on some sort of pain meds. If they were the solution, they wouldn’t call our front desk staff for an appointment.

            I did once refer to you(jokingly and with a smiley face afterwards) as a lab rat. You need to get of your desk mate, and off your computer, and maybe back in the real world we live in before you say everything a musculoskeletal practitioner does is a waste of time. And I’m not talking about a vitality based chiro…as they are dying off fast in the real clinical world.

            Ps. I’m typing this on my iPhone. I hope it reads correct. 🙁

          • how do you know that complications of drugs are “much higher” when there is no monitoring system that gives us any information about AEs of SMT
            did I say that all what patients need are drugs?
            and that [“I did once refer to you(jokingly and with a smiley face afterwards) as a lab rat. You need to get of your desk mate, and off your computer, and maybe back in the real world we live in before you say everything a musculoskeletal practitioner does is a waste of time”] is not even funny – just uninformed and stupid, in my view.

          • The studies you refer to suggest that nasaids are just as effective as spinal mobs/manips.

            What studies? The one at discussion here does not. The correct acronym for the family of antiinflamatory and pain relieving medications is “NSAID” – Non Steroidal Anti-Inflamatory Drugs. “Nasaids” sounds like a trade name for a nasal decongestant. (You called for this quip by declaring you prescribe them 😉 )
            If they were anywhere as dangerous as quacks proclaim, they would not be some of the most used medications in the world.

            But the risk of something “going wrong” and causing death or at the very least some serious complication are much higher with nasaids.

            Evidence please. NSAID’s work. Properly used and monitored, NSAID’s are as safe as any drug. I have taken diclofenak for years, My grandfather died “healthy” at the age of 92. He had eaten indometacinlike candy (literally!) for several decades to be able to live with our familial osteoarthritis that ruined his knees. I would be an invalid without NSAID’s Believe me I’ve tried. The risk is manageable and worth it.
            Neck adjustments have not been proven to work beyond the effects of good theatrical placebo. They are dispensible in order to avoid the risk of death, locked-in syndrome and invalidity in young people. Risk/benefit ratio is the important measure here.

            … I do prescribe nasaids to patients… …But to suggest that these meds are the only thing that a particular patient with back or neck pain needs is just not realistic in the clinical world that the DC/DO/Physio lives in.

            Who suggested that and where?

            Most of the patients that enter our clinics are already on some sort of pain meds. If they were the solution, they wouldn’t call our front desk staff for an appointment.

            Non-sequitur. You will at least have to define “solution” if you wish to defend this argument.

            You need to get of your desk mate, and off your computer, and maybe back in the real world we live in before you say everything a musculoskeletal practitioner does is a waste of time. And I’m not talking about a vitality based chiro…as they are dying off fast in the real clinical world.

            Where is the evidence? I do not see it. The chiro-community in my part of the world is full of practice building balloney and bullshit about being able to cure anything from Allergy to Zoster by repeatedly thumping on and twisting the spine. When the demand did not meet the supply, chiropractors even made up, out of blue air, a pediatric proficiency for themselves.
            On Facebook, Youtube and self-promotion websites they serve worried parents with straight lies like the one about 95% of babies being born with a misalignment* requiring their ministrations. This is charlatanry for all the money.
            This real-world-reality is right before our eyes on the various social media and internet sites. Before, we had to take the car out to fetch information. Now I can browse all of it right here at 38000 feet above the North-Atlantic. In my comfortable chair. The net is where potential clients are phished and led with half-truths and deceptions into the parlours of practitioning quacks, who stuff their heads deep into the sand when people like us point out a potentially devastating health threat from their ministrations.
            Now who is it that needs a reality check!!
            *The image I intended as proof does not want to upload to through the connection in the transatlantic plane I sit in at the moment. I will provide a link to it later upon request. Several versions of it are commonly spread in Chiro-Facebook-pages, Pinterest etc. and may be found by Googling the text: “95% of infants have misalignments after birth“.

          • Same authors in Spine Dec 2014! Conclusions are extremely interesting!!!
            Risk of Traumatic Injury Associated with Chiropractic Spinal Manipulation in Medicare Part B Beneficiaries Aged 66-99.
            The Spine Journal 2013! Interesting!
            Trends in the use and cost of chiropractic spinal manipulation under Medicare Part B.

  • I stumbled over a case report that deserves mention here.

    I particularly like one sentence in the conclusion, seeing as the paper is published in a journal called “Chiropractic and Manual therapies”
    (my emphasis)

    It is possible that the arterial dissection had occurred prior to seeking treatment, and may have become evident if the patient had sought the care of a general practitioner rather than a chiropractor.

    How true.
    Goes to strengthen my conviction, that not only are adverse events from chiropractic ministrations entirely preventable.
    The world would be a better place if money spent on make-believe “primary care” would go to reinforce and improve genuine primary care.

    There are several more case reports on other post neck “adjustment” related AE’s than VBD. Carotid dissections, Horner’s syndrome etc. Of course case reports do not causal evidence make. But as we are constantly pointing out:
    There are dead and injured lying about and the chiropractor’s guns are smoking and the barrels feel warm. Who shot who? And where’s the Sheriff now that we need one?

  • There have been some interesting comments above about NSAID’s and yet this is only just now being done and by a physio!
    Interesting what!
    PACE – The first placebo controlled trial of paracetamol for acute low back pain: design of a randomised controlled trial
    PACE – the first placebo controlled trial of paracetamol for acute low back pain: statistical analysis plan

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