MD, PhD, FMedSci, FSB, FRCP, FRCPEd

causation

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A recent comment to a post of mine (by a well-known and experienced German alt med researcher) made the following bold statement aimed directly at me and at my apparent lack of understanding research methodology:

C´mon , as researcher you should know the difference between efficacy and effectiveness. This is pharmacological basic knowledge. Specific (efficacy) + nonspecific effects = effectiveness. And, in fact, everything can be effective – because of non-specific or placebo-like effects. That does not mean that efficacy is existent.

The point he wanted to make is that outcome studies – studies without a control group where the researcher simply observe the outcome of a particular treatment in a ‘real life’ situation – suffice to demonstrate the effectiveness of therapeutic interventions. This belief is very wide-spread in alternative medicine and tends to mislead all concerned. It is therefore worth re-visiting this issue here in an attempt to create some clarity.

When a patient’s condition improves after receiving a therapy, it is very tempting to feel that this improvement reflects the effectiveness of the intervention (as the researcher mentioned above obviously does). Tempting but wrong: there are many other factors involved as well, for instance:

  • the placebo effect (mainly based on conditioning and expectation),
  • the therapeutic relationship with the clinician (empathy, compassion etc.),
  • the regression towards the mean (outliers tend to return to the mean value),
  • the natural history of the patient’s condition (most conditions get better even without treatment),
  • social desirability (patients tend to say they are better to please their friendly clinician),
  • concomitant treatments (patients often use treatments other than the prescribed one without telling their clinician).

So, how does this fit into the statement above ‘Specific (efficacy) + nonspecific effects = effectiveness’? Even if this formula were correct, it would not mean that outcome studies of the nature described demonstrate the effectiveness of a therapy. It all depends, of course, on what we call ‘non-specific’ effects. We all agree that placebo-effects belong to this category. Probably, most experts also would include the therapeutic relationship and the regression towards the mean under this umbrella. But the last three points from my list are clearly not non-specific effects of the therapy; they are therapy-independent determinants of the clinical outcome.

The most important factor here is usually the natural history of the disease. Some people find it hard to imagine what this term actually means. Here is a little joke which, I hope, will make its meaning clear and memorable.

CONVERATION BETWEEN TWO HOSPITAL DOCTORS:

Doc A: The patient from room 12 is much better today.

Doc B: Yes, we stared his treatment just in time; a day later and he would have been cured without it!

I am sure that most of my readers now understand (and never forget) that clinical improvement cannot be equated with the effectiveness of the treatment administered (they might thus be immune to the misleading messages they are constantly exposed to). Yet, I am not at all sure that all ‘alternativists’ have got it.

In my last post, I claimed that researchers of alternative medicine tend to be less than rigorous. I did not link this statement to any evidence at all. Perhaps I should have at least provided an example!? As it happens, I just came across a brand new paper which nicely demonstrates what I meant.

According to its authors, this non-interventional study was performed to generate data on safety and treatment effects of a complex homeopathic drug. They treated 1050 outpatients suffering from common cold with a commercially available homeopathic remedy for 8 days. The study was conducted in 64 German outpatient practices of medical doctors trained in CAM. Tolerability, compliance and the treatment effects were assessed by the physicians and by patient diaries. Adverse events were collected and assessed with specific attention to homeopathic aggravation and proving symptoms. Each adverse effect was additionally evaluated by an advisory board of experts.

The physicians detected 60 adverse events from 46 patients (4.4%). Adverse drug reactions occurred in 14 patients (1.3%). Six patients showed proving symptoms (0.57%) and only one homeopathic aggravation (0.1%) appeared. The rate of compliance was 84% for all groups. The global assessment of the treatment effects resulted in the verdict “good” and “very good” in 84.9% of all patients.

The authors concluded that the homeopathic complex drug was shown to be safe and effective for children and adults likewise. Adverse reactions specifically related to homeopathic principles are very rare. All observed events recovered quickly and were of mild to moderate intensity.

So why do I think this is ‘positively barmy’?

The study had no control group. This means that there is no way anyone can attribute the observed ‘treatment effects’ to the homeopathic remedy. There are many other phenomena that may have caused or contributed to it, e. g.:

  • a placebo effect
  • the natural history of the condition
  • regression to the mean
  • other treatments which the patients took but did not declare
  • the empathic encounter with the physician
  • social desirability

To plan a study with the aim as stated above and to draw the conclusion as cited above is naïve and unprofessional (to say the least) on the part of the researchers (I often wonder where, in such cases, the boundary between incompetence and research misconduct might lie). To pass such a paper through the peer review process is negligent on the part of the reviewers. To publish the article is irresponsible on the part of the editor.

In a nut-shell: COLLECTIVELY, THIS IS ‘POSITIVELY BARMY’!!!

Yoga is a popular form of alternative medicine. Evidence for its effectiveness is scarce and generally far from convincing. But at least it is safe! At least this is what yoga enthusiasts would claim. Unfortunately, this is not entirely true; adverse events have also been reported with some regularity. Their frequency is, however, not known.

A new study was aimed at filling this gap. It was conducted to elucidate the frequencies and characteristics of adverse events of yoga performed in classes and the risk factors of such events.

The subjects were 2508 people taking yoga classes and 271 yoga therapists conducting the classes. A survey for yoga class attendees was performed on adverse events that occurred during a yoga class on the survey day. A survey for yoga therapists was performed on adverse events that the therapists had observed in their students to date. Adverse events were defined as “undesirable symptoms or responses that occurred during a yoga class”.

Among 2508 yoga class attendees, 1343 (53.5%) had chronic diseases and 1063 (42.3%) were receiving medication at hospitals. There were 687 class attendees (27.8%) who reported some type of undesirable symptoms after taking a yoga class. Musculoskeletal symptoms such as myalgia were the most common symptoms, involving 297 cases, followed by neurological symptoms and respiratory symptoms. Most adverse events (63.8%) were mild and did not interfere with class participation. The risk factors for adverse events were examined, and the odds ratios for adverse events were significantly higher in attendees with chronic disease, poor physical condition on the survey day, or a feeling that the class was physically and mentally stressful. In particular, the occurrence of severe adverse events that interfered with subsequent yoga practice was high among elderly participants (70 years or older) and those with chronic musculoskeletal diseases.

The authors concluded that the results of this large-scale survey demonstrated that approximately 30% of yoga class attendees had experienced some type of adverse event. Although the majority had mild symptoms, the survey results indicated that attendees with chronic diseases were more likely to experience adverse events associated with their disease. Therefore, special attention is necessary when yoga is introduced to patients with stress-related, chronic diseases.

I find these findings interesting and thought-provoking. The main question that they raise is, I think, the flowing: ARE THERE ANY CONDITIONS FOR WHICH YOGA DEMONSTRABLY GENERATES MORE GOOD THAN HARM?

Distant healing is one of the most bizarre yet popular forms of alternative medicine. Healers claim they can transmit ‘healing energy’ towards patients to enable them to heal themselves. There have been many trials testing the effectiveness of the method, and the general consensus amongst critical thinkers is that all variations of ‘energy healing’ rely entirely on a placebo response. A recent and widely publicised paper seems to challenge this view.

This article has, according to its authors, two aims. Firstly it reviews healing studies that involved biological systems other than ‘whole’ humans (e.g., studies of plants or cell cultures) that were less susceptible to placebo-like effects. Secondly, it presents a systematic review of clinical trials on human patients receiving distant healing.

All the included studies examined the effects upon a biological system of the explicit intention to improve the wellbeing of that target; 49 non-whole human studies and 57 whole human studies were included.

The combined weighted effect size for non-whole human studies yielded a highly significant (r = 0.258) result in favour of distant healing. However, outcomes were heterogeneous and correlated with blind ratings of study quality; 22 studies that met minimum quality thresholds gave a reduced but still significant weighted r of 0.115.

Whole human studies yielded a small but significant effect size of r = .203. Outcomes were again heterogeneous, and correlated with methodological quality ratings; 27 studies that met threshold quality levels gave an r = .224.

From these findings, the authors drew the following conclusions: Results suggest that subjects in the active condition exhibit a significant improvement in wellbeing relative to control subjects under circumstances that do not seem to be susceptible to placebo and expectancy effects. Findings with the whole human database suggests that the effect is not dependent upon the previous inclusion of suspect studies and is robust enough to accommodate some high profile failures to replicate. Both databases show problems with heterogeneity and with study quality and recommendations are made for necessary standards for future replication attempts.

In a press release, the authors warned: the data need to be treated with some caution in view of the poor quality of many studies and the negative publishing bias; however, our results do show a significant effect of healing intention on both human and non-human living systems (where expectation and placebo effects cannot be the cause), indicating that healing intention can be of value.

My thoughts on this article are not very complimentary, I am afraid. The problems are, it seems to me, too numerous to discuss in detail:

  • The article is written such that it is exceedingly difficult to make sense of it.
  • It was published in a journal which is not exactly known for its cutting edge science; this may seem a petty point but I think it is nevertheless important: if distant healing works, we are confronted with a revolution in the understanding of nature – and surely such a finding should not be buried in a journal that hardly anyone reads.
  • The authors seem embarrassingly inexperienced in conducting and publishing systematic reviews.
  • There is very little (self-) critical input in the write-up.
  • A critical attitude is necessary, as the primary studies tend to be by evangelic believers in and amateur enthusiasts of healing.
  • The article has no data table where the reader might learn the details about the primary studies included in the review.
  • It also has no table to inform us in sufficient detail about the quality assessment of the included trials.
  • It seems to me that some published studies of distant healing are missing.
  • The authors ignored all studies that were not published in English.
  • The method section lacks detail, and it would therefore be impossible to conduct an independent replication.
  • Even if one ignored all the above problems, the effect sizes are small and would not be clinically important.
  • The research was sponsored by the ‘Confederation of Healing Organisations’ and some of the comments look as though the sponsor had a strong influence on the phraseology of the article.

Given these reservations, my conclusion from an analysis of the primary studies of distant healing would be dramatically different from the one published by the authors: DESPITE A SIZABLE AMOUNT OF PRIMARY STUDIES ON THE SUBJECT, THE EFFECTIVENESS OF DISTANT HEALING REMAINS UNPROVEN. AS THIS THERAPY IS BAR OF ANY BIOLOGICAL PLAUSIBILITY, FURTHER RESEARCH IN THIS AREA SEEMS NOT WARRANTED.

Twenty years ago, I published a short article in the British Journal of Rheumatology. Its title was ALTERNATIVE MEDICINE, THE BABY AND THE BATH WATER. Reading it again today – especially in the light of the recent debate (with over 700 comments) on acupuncture – indicates to me that very little has since changed in the discussions about alternative medicine (AM). Does that mean we are going around in circles? Here is the (slightly abbreviated) article from 1995 for you to judge for yourself:

“Proponents of alternative medicine (AM) criticize the attempt of conducting RCTs because they view this is in analogy to ‘throwing out the baby with the bath water’. The argument usually goes as follows: the growing popularity of AM shows that individuals like it and, in some way, they benefit through using it. Therefore it is best to let them have it regardless of its objective effectiveness. Attempts to prove or disprove effectiveness may even be counterproductive. Should RCTs prove that a given intervention is not superior to a placebo, one might stop using it. This, in turn, would be to the disadvantage of the patient who, previous to rigorous research, has unquestionably been helped by the very remedy. Similar criticism merely states that AM is ‘so different, so subjective, so sensitive that it cannot be investigated in the same way as mainstream medicine’. Others see reasons to change the scientific (‘reductionist’) research paradigm into a broad ‘philosophical’ approach. Yet others reject the RCTs because they think that ‘this method assumes that every person has the same problems and there are similar causative factors’.

The example of acupuncture as a (popular) treatment for osteoarthritis, demonstrates the validity of such arguments and counter-arguments. A search of the world literature identified only two RCTs on the subject. When acupuncture was tested against no treatment, the experimental group of osteoarthritis sufferers reported a 23% decrease of pain, while the controls suffered a 12% increase. On the basis of this result, it might seem highly unethical to withhold acupuncture from pain-stricken patients—’if a patient feels better for whatever reason and there are no toxic side effects, then the patient should have the right to get help’.

But what about the placebo effect? It is notoriously difficult to find a placebo indistinguishable to acupuncture which would allow patient-blinded studies. Needling non-acupuncture points may be as close as one can get to an acceptable placebo. When patients with osteoarthritis were randomized into receiving either ‘real acupuncture or this type of sham acupuncture both sub-groups showed the same pain relief.

These findings (similar results have been published for other AMs) are compatible only with two explanations. Firstly acupuncture might be a powerful placebo. If this were true, we need to establish how safe acupuncture is (clearly it is not without potential harm); if the risk/benefit ratio is favourable and no specific, effective form of therapy exists one might still consider employing this form as a ‘placebo therapy’ for easing the pain of osteoarthritis sufferers. One would also feel motivated to research this powerful placebo and identify its characteristics or modalities with the aim of using the knowledge thus generated to help future patients.

Secondly, it could be the needling, regardless of acupuncture points and philosophy, that decreases pain. If this were true, we could henceforward use needling for pain relief—no special training in or equipment for acupuncture would be required, and costs would therefore be markedly reduced. In addition, this knowledge would lead us to further our understanding of basic mechanisms of pain reduction which, one day, might evolve into more effective analgesia. In any case the published research data, confusing as they often are, do not call for a change of paradigm; they only require more RCTs to solve the unanswered problems.

Conducting rigorous research is therefore by no means likely to ‘throw out the baby with the bath water’. The concept that such research could harm the patient is wrong and anti-scientific. To follow its implications would mean neglecting the ‘baby in the bath water’ until it suffers serious damage. To conduct proper research means attending the ‘baby’ and making sure that it is safe and well.

If we listen to acupuncturists and their supporters, we might get the impression that acupuncture is totally devoid of risk. Readers of this blog will know that this is not quite true. A recent case report is a further reminder that acupuncture can cause serious complications; in extreme cases it can even kill.

A male patient in his late forties died right after an acupuncture treatment. A medico-legal autopsy disclosed severe haemorrhaging around the right vagus nerve in the neck. All other organs were normal, and laboratory findings revealed nothing significant. Thus, the authors of this case-report concluded that the man most probably died from severe vagal bradycardia and/or arrhythmia resulting from vagus nerve stimulation following acupuncture: To the best of our knowledge, this is the first report of a death due to vagus nerve injury after acupuncture.

In total, around 100 deaths have been reported after acupuncture in the medical literature. ‘This is a negligible small figure’ claim acupuncture fans. True, it is a small number, but it could just be the tip of a much larger ice-berg: there is no reporting system that could possibly pick up severe complications, and in the absence of such a scheme, nobody can name reliable incidence rates. And even if the numbers of severe complications and deaths are small – even a single fatality would seem one too many.

The deaths that are currently on record are mostly due to bilateral pneumothorax or cardiac tamponade. The present case of vagus nerve injury seems to be ‘a first’. Perhaps we should watch out for similar events?

IF WE DON’T LOOK, WE DON’T SEE.

Reflexology is the treatment of reflex zones, usually on the sole of the feet, with manual massage and pressure. Reflexologists assume that certain zones correspond to certain organs, and that their treatment can influence the function of these organs. Thus reflexology is advocated for all sorts of conditions. Proponents are keen to point out that their approach has many advantages: it is pleasant (the patient feels well with the treatment and the therapist feels even better with the money), safe and cheap, particularly if the patient does the treatment herself.

Self-administered foot reflexology could be practical because it is easy to learn and not difficult to apply. But is it also effective? A recent systematic review evaluated the effectiveness of self-foot reflexology for symptom management.

Participants were healthy persons not diagnosed with a specific disease. The intervention was foot reflexology administered by participants, not by practitioners or healthcare providers. Studies with either between groups or within group comparison were included. The electronic literature searches utilized core databases (MEDLINE, EMBASE, Cochrane, and CINAHL Chinese (CNKI), Japanese (J-STAGE), and Korean databases (KoreaMed, KMbase, KISS, NDSL, KISTI, and OASIS)).

Three non-randomized trials and three before-and-after studies met the inclusion criteria. No RCTs were located. The results of these studies showed that self-administered foot reflexology resulted in significant improvement in subjective outcomes such as perceived stress, fatigue, and depression. However, there was no significant improvement in objective outcomes such as cortisol levels, blood pressure, and pulse rate. We did not find any randomized controlled trial.

The authors concluded that this study presents the effectiveness of self-administered foot reflexology for healthy persons’ psychological and physiological symptoms. While objective outcomes showed limited results, significant improvements were found in subjective outcomes. However, owing to the small number of studies and methodological flaws, there was insufficient evidence supporting the use of self-performed foot reflexology. Well-designed randomized controlled trials are needed to assess the effect of self-administered foot reflexology in healthy people.

I find this review quite interesting, but I would draw very different conclusions from its findings.

The studies that are available turned out to be of very poor methodological quality: they lack randomisation or rely on before/after comparisons. This means they are wide open to bias and false-positive results, particularly in regards to subjective outcome measures. Predictably, the findings of this review confirm that no effects are seen on objective endpoints. This is in perfect agreement with the hypothesis that reflexology is a pure placebo. Considering the biological implausibility of the underlying assumptions of reflexology, this makes sense.

My conclusions of this review would therefore be as follows: THE RESULTS ARE IN KEEPING WITH REFLEXOLOGY BEING A PURE PLACEBO.

Homeopathy has many critics who claim that there is no good evidence for this type of therapy. Homeopaths invariably find this most unfair and point to a plethora of studies that show an effect. They are, of course, correct! There are plenty of trials that suggest that homeopathic remedies do work. The question, however, is HOW RELIABLE ARE THESE STUDIES?

Here is a brand new one which might stand for dozens of others.

In this study, homeopaths treated 50 multimorbid patients with homeopathic remedies identifies by a method called ‘polarity analysis’ (PA) and prospectively followed them over one year (PA enables homeopaths to calculate a relative healing probability, based on Boenninghausen’s grading of polar symptoms).

The 43 patients (86%) who completed the observation period experienced an average improvement of 91% in their initial symptoms. Six patients dropped out, and one did not achieve an improvement of 80%, and was therefore also counted as a treatment failure. The cost of homeopathic treatment was 41% of projected equivalent conventional treatment.

Good news then for enthusiasts of homeopathy? 91% improvement!

Yet, I am afraid that critics might not be bowled over. They might smell a whiff of selection bias, lament the lack of a control group or regret the absence of objective outcome measures. But I was prepared to go as far as stating that such results might be quite interesting… until I read the authors’ conclusions that is:

Polarity Analysis is an effective method for treating multimorbidity. The multitude of symptoms does not prevent the method from achieving good results. Homeopathy may be capable of taking over a considerable proportion of the treatment of multimorbid patients, at lower costs than conventional medicine.

Virtually nothing in these conclusions is based on the data provided. They are pure extrapolation and wild assumptions. Two questions seem to emerge from this:

  1. How on earth can we take this and so many other articles on homeopathy seriously?
  2. When does this sort of article cross the line between wishful thinking and scientific misconduct?

On 1/12/2014 I published a post in which I offered to give lectures to students of alternative medicine:

Getting good and experienced lecturers for courses is not easy. Having someone who has done more research than most working in the field and who is internationally known, might therefore be a thrill for students and an image-boosting experience of colleges. In the true Christmas spirit, I am today making the offer of being of assistance to the many struggling educational institutions of alternative medicine .

A few days ago, I tweeted about my willingness to give free lectures to homeopathic colleges (so far without response). Having thought about it a bit, I would now like to extend this offer. I would be happy to give a free lecture to the students of any educational institution of alternative medicine.

I did not think that this would create much interest – and I was right: only the ANGLO-EUROPEAN COLLEGE OF CHIROPRACTIC has so far hoisted me on my own petard and, after some discussion (see comment section of the original post) hosted me for a lecture. Several people seem keen on knowing how this went; so here is a brief report.

I was received, on 14/1/2015, with the utmost kindness by my host David Newell. We has a coffee and a chat and then it was time to start the lecture. The hall was packed with ~150 students and the same number was listening in a second lecture hall to which my talk was being transmitted.

We had agreed on the title CHIROPRACTIC: FALLACIES AND FACTS. So, after telling the audience about my professional background, I elaborated on 7 fallacies:

  1. Appeal to tradition
  2. Appeal to authority
  3. Appeal to popularity
  4. Subluxation exists
  5. Spinal manipulation is effective
  6. Spinal manipulation is safe
  7. Ad hominem attack

Numbers 3, 5 and 6 were dealt with in more detail than the rest. The organisers had asked me to finish by elaborating on what I perceive as the future challenges of chiropractic; so I did:

  1. Stop happily promoting bogus treatments
  2. Denounce obsolete concepts like ‘subluxation’
  3. Clarify differences between chiros, osteos and physios
  4. Start a culture of critical thinking
  5. Take action against charlatans in your ranks
  6. Stop attacking everyone who voices criticism

I ended by pointing out that the biggest challenge, in my view, was to “demonstrate with rigorous science which chiropractic treatments demonstrably generate more good than harm for which condition”.

We had agreed that my lecture would be followed by half an hour of discussion; this period turned out to be lively and had to be extended to a full hour. Most questions initially came from the tutors rather than the students, and most were polite – I had expected much more aggression.

In his email thanking me for coming to Bournemouth, David Newell wrote about the event: The general feedback from staff and students was one of relief that you possessed only one head, :-). I hope you may have felt the same about us. You came over as someone who had strong views, a fair amount of which we disagreed with, but that presented them in a calm, informative and courteous manner as we did in listening and discussing issues after your talk. I think everyone enjoyed the questions and debate and felt that some of the points you made were indeed fair critique of what the profession may need to do, to secure a more inclusive role in the health care arena.

 
As you may have garnered from your visit here, the AECC is committed to this task as we continue to provide the highest quality of education for the 21st C representatives of such a profession. We believe centrally that it is to our society at large and our communities within which we live and work that we are accountable. It is them that we serve, not ourselves, and we need to do that as best we can, with the best tools we have or can develop and that have as much evidence as we can find or generate. In this aim, your talk was important in shining a more ‘up close and personal’ torchlight on our profession and the tasks ahead whilst also providing us with a chance to debate the veracity or otherwise of yours and ours differing positions on interpretation of the evidence.

My own impression of the day is that some of my messages were not really understood, that some of the questions, including some from the tutors, seemed like coming from a different planet, and that people were more out to teach me than to learn from my talk. One overall impression that I took home from that day is that, even in this college which prides itself of being open to scientific evidence and unimpressed by chiropractic fundamentalism, students are strangely different from other health care professionals. The most tangible aspect of this is the openly hostile attitude against drug therapies voiced during the discussion by some students.

The question I always ask myself after having invested a lot of time in preparing and delivering a lecture is: WAS IT WORTH IT? In the case of this lecture, I think the answer is YES. With 300 students present, I am fairly confident that I did manage to stimulate a tiny bit of critical thinking in a tiny percentage of them. The chiropractic profession needs this badly!

 

The very first article on a subject related to alternative medicine with a 2015 date that I came across is a case-report. I am afraid it will not delight our chiropractic friends who tend to deny that their main therapy can cause serious problems.

In this paper, US doctors tell the story of a young woman who developed headache, vomiting, diplopia, dizziness, and ataxia following a neck manipulation by her chiropractor. A computed tomography scan of the head was ordered and it revealed an infarct in the inferior half of the left cerebellar hemisphere and compression of the fourth ventricle causing moderately severe, acute obstructive hydrocephalus. Magnetic resonance angiography showed severe narrowing and low flow in the intracranial segment of the left distal vertebral artery. The patient was treated with mannitol and a ventriculostomy. Following these interventions, she made an excellent functional recovery.

The authors of the case-report draw the following conclusions: This report illustrates the potential hazards associated with neck trauma, including chiropractic manipulation. The vertebral arteries are at risk for aneurysm formation and/or dissection, which can cause acute stroke.

I can already hear the counter-arguments: this is not evidence, it’s an anecdote; the evidence from the Cassidy study shows there is no such risk!

Indeed the Cassidy study concluded that vertebral artery accident (VBA) stroke is a very rare event in the population. The increased risks of VBA stroke associated with chiropractic and primary care physician visits is likely due to patients with headache and neck pain from VBA dissection seeking care before their stroke. We found no evidence of excess risk of VBA stroke associated chiropractic care compared to primary care. That, of course, was what chiropractors longed to hear (and it is the main basis for their denial of risk) – so much so that Cassidy et al published the same results a second time (most experts feel that this is a violation of publication ethics).

But repeating arguments does not make them more true. What we should not forget is that the Cassidy study was but one of several case-control studies investigating this subject. And the totality of all such studies does not deny an association between neck manipulation and stroke.

Much more important is the fact that a re-analysis of the Cassidy data found that prior studies grossly misclassified cases of cervical dissection and mistakenly dismissed a causal association with manipulation. The authors of this new paper found a classification error of cases by Cassidy et al and they re-analysed the Cassidy data, which reported no association between spinal manipulation and cervical artery dissection (odds ratio [OR] 5 1.12, 95% CI .77-1.63). These re-calculated results reveal an odds ratio of 2.15 (95% CI.98-4.69). For patients less than 45 years of age, the OR was 6.91 (95% CI 2.59-13.74). The authors of the re-analysis conclude as follows: If our estimates of case misclassification are applicable outside the VA population, ORs for the association between SMT exposure and CAD are likely to be higher than those reported using the Rothwell/Cassidy strategy, particularly among younger populations. Future epidemiologic studies of this association should prioritize the accurate classification of cases and SMT exposure.
I think they are correct; but my conclusion of all this would be more pragmatic and much simpler: UNTIL WE HAVE CONVINCING EVIDENCE TO THE CONTRARY, WE HAVE TO ASSUME THAT CHIROPRACTIC NECK MANIPULATION CAN CAUSE A STROKE.

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