MD, PhD, FMedSci, FSB, FRCP, FRCPEd

risk

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There are things that cannot be said too often. In medicine, these are often related to issues that can save lives. In alternative medicine, it is worth remembering that there is nothing that can save more lives than the following rule: EVEN AN APPARENTLY HARMLESS REMEDY WILL BECOME LIFE-THREATENING, IF IT IS USED AS AN ALTERNATIVE TO AN EFFECTIVE THERAPY FOR A SERIOUS CONDITION.

Here is a publication that serves as a very sad reminder of this important axiom.

Japanese physicians recently published a case-report of 2-year-old girl who died of precursor B-cell acute lymphoblastic leukaemia (ALL), the most common cancer in children. She had no remarkable medical history. She was transferred to a hospital because of respiratory distress and died 4 hours after arrival.

Two weeks before her death, she had developed a fever of 39°C, which subsided after the administration of a naturopathic herbal remedy. Subsequently, she developed jaundice one week before death, and her condition worsened on the day of death.

Laboratory test results on admission showed a markedly elevated white blood cell count. Accordingly, the cause of death was suspected to be acute leukaemia. Forensic autopsy revealed the cause of death to be precursor B-cell ALL.

With advancements in medical technology, the 5-year survival rate of children with ALL is nearly 90%. However, in this case, the deceased’s parents preferred alternative medicine to evidence-based medicine and had not taken her to a hospital for a medical check-up or immunisation since she was an infant. The authors state that, if she had received routine medical care, she would have a more than 60% chance of being alive 5 years after diagnosis. Therefore, we conclude that the parents should be accused of medical neglect regardless of their motives.

Alternative practitioners who treat their patients in this way, are in my experience often full of good intentions. They remind me of something Bert Brecht one wrote: THE OPPOSITE OF GOOD IS NOT EVIL, IT IS GOOD INTENTIONS.

Ayurvedic medicine has become highly popular in Western countries; it originates, of course, from India, and is considered to be one of the world’s oldest health care systems. Its adherents claim to create harmony between the body, mind, and spirit, maintaining that this balance prevents illness, treats acute conditions, and contributes to a long and healthy life. In India Ayurveda is mainstream and more than 90% of the population are said to use it. Outside India, Ayurveda is usually classified as an alternative therapy.

Ayurvedic treatments can consist of a range of modalities, including herbal remedies taken by mouth. These preparations have often been reported to be contaminated with toxic metals. Despite several case reports of poisoning from such contamination, the epidemiological evidence is still limited. A new paper on this important topic is therefore welcome. It reports on a cluster of lead and mercury toxicity cases which occurred 2011 among a community of users of Ayurvedic remedies in the US.

Following the identification of the index case, adherents of Ayurveda were offered heavy metals screening. The results showed that 46 of 115 participants (40%) had elevated blood lead levels (BLLs) of 10 μg/dl or above, with 9.6% of BLLs at or above 50 μg/dl.

The authors issued the following warning: this is the largest cluster of lead and mercury toxicity following use of Ayurvedic supplements described in the literature in the US. Contamination of herbal products is a public health issue of global significance. There are few regulations addressing contamination of “natural” products or supplements.

Rasa shastra, the practice of adding metals, minerals or gems to herbal preparations, is a well-documented part of Ayurveda. Adverse reactions to herbs are described in traditional Ayurvedic texts, but practitioners tend to be reluctant to admit that their remedies could be toxic and that reliable information on their risks is not readily available.

Already in 1990, a study on Ayurvedic medicines in India found that 41% of the products tested contained arsenic, and that 64% contained lead and mercury. A 2004 study found toxic levels of heavy metals in 20% of Ayurvedic preparations sold in the Boston area. A 2008 study of more than 230 products found that approximately 20% of remedies (and 40% of rasa shastra medicines) purchased over the Internet from U.S. and Indian suppliers contained lead, mercury or arsenic.

My 2002 systematic review summarised all the available evidence and concluded that heavy metals, particularly lead, have been a regular constituent of traditional Indian remedies. This has repeatedly caused serious harm to patients taking such remedies. The incidence of heavy metal contamination is not known, but one study shows that 64% of samples collected in India contained significant amounts of lead (64% mercury, 41% arsenic and 9% cadmium). These findings should alert us to the possibility of heavy metal content in traditional Indian remedies and motivate us to consider means of protecting consumers from such risks.

Despite these concerns, Ayurveda-fans continue to believe that the toxicity of these remedies is reduced through the purification processes of Ayurvedic remedy preparation. Bizarrely, they may involve prayers as well as physical pharmacy techniques.

The Indian government ruled that Ayurvedic products must be labelled with their metallic content. However, one Indian expert, has been quoted claiming that “the absence of post-market surveillance and the paucity of test laboratory facilities [in India] make the quality control of Ayurvedic medicines exceedingly difficult at this time”. In the US, most Ayurvedic products are marketed without having been approved by the FDA. Since 2007, the FDA has placed an import alert on some Ayurvedic products in order to prevent them from entering the US.

Protecting consumers from heavy metal poisoning by Ayurvedic remedies is certainly not easy – but, in the interest of public health, it is a task that we must tackle with some ungency.

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?

One of the UK’s most ardent promoters of outright unproven and disproven therapies must be Dr Michael Dixon. He has repeatedly and deservedly received a mention on this blog. Steven Novella even called him once a ‘pyromaniac in a field of (integrative) straw men’. This is because Steven felt that Dixon uses phony arguments to promote dodgy therapies. If you find this hard to believe (after all Dixon is a GP who heads important organisations such as the NHS Alliance and the College of Medicine), just look at him dabbling in spiritual healing. Unusual, to say the least, I’d say. If you want to learn more about the strange Dr Dixon, you should read my memoir where he makes several remarkable appearances.

I always delight when I stumble over something that one of my former co-workers (yes, Dixon and I did collaborate for many years) has said to the press. This is why an otherwise silly article in the Daily Mail (yes, I know!) caught my attention; here is the relevant section: Dr Mike Dixon, a GP in Cullompton, Devon, and chairman of the College of Medicine, says he is a ‘fan’ of herbal medicines because they are ‘safe, help to encourage self-care by patients and, in cases such as mint and aloe vera, can be grown by the patients themselves, making them virtually free’.

As I already pointed out, Dixon does tend to promote bizarre concepts. The generalisation that herbal remedies are safe is not just bizarre, it also put the public at risk. One does not need to search long to find an article that makes this clear:

Various reports suggest a high contemporaneous prevalence of herb-drug use in both developed and developing countries. The World Health Organisation indicates that 80% of the Asian and African populations rely on traditional medicine as the primary method for their health care needs. Since time immemorial and despite the beneficial and traditional roles of herbs in different communities, the toxicity and herb-drug interactions that emanate from this practice have led to severe adverse effects and fatalities. As a result of the perception that herbal medicinal products have low risk, consumers usually disregard any association between their use and any adverse reactions hence leading to underreporting of adverse reactions. This is particularly common in developing countries and has led to a paucity of scientific data regarding the toxicity and interactions of locally used traditional herbal medicine. Other factors like general lack of compositional and toxicological information of herbs and poor quality of adverse reaction case reports present hurdles which are highly underestimated by the population in the developing world. This review paper addresses these toxicological challenges and calls for natural health product regulations as well as for protocols and guidance documents on safety and toxicity testing of herbal medicinal products.

Dixon once told me that GPs do not any longer read scientific papers. I think, however, that he should start doing so before the next time he misinform the public and endangers the health of vulnerable people.

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.

Neck pain is a common problem which often causes significant disability. Chiropractic manipulation has become one of the most popular forms of alternative treatment for such symptoms. This seems surprising considering that neck manipulations are neither convincingly effective nor free of adverse effects.

The current Cochrane review on this subject could not be clearer: “Done alone, manipulation and/or mobilization were not beneficial; when compared to one another, neither was superior.” In the absence of compelling evidence for efficacy, any risk of neck manipulation would tilt the risk/benefit balance into the negative.

Adverse effects of neck manipulations range from mild symptoms, such as local neck tenderness or stiffness, to more severe injuries involving the spinal cord, peripheral nerve roots, and arteries within the neck. A recent paper reminds us that another serious complication has to be added to this already long list: phrenic nerve injury.

The phrenic nerve is responsible for controlling the contractions of the diaphragm, which allows the lungs to take in and release air and make us breathe properly. The phrenic nerve is formed from C3, C4, and C5 nerve fibres and descends along the anterior surface of the scalenus anterior muscle before entering the thorax to supply motor and sensory input to the diaphragm. Its anatomic location in the neck leaves it vulnerable to traumatic injury. Phrenic nerve injury can result in paralysis of the diaphragm and often leads to deteriorating function of the diaphragm, which can lead to partial or complete paralysis of the muscle and, as a result, serious breathing problems.

Patients who experience such problems may require emergency medical treatment or surgery. Sudden, severe damage to the phrenic nerve can make it impossible for the diaphragm to contract on its own. In order to make sure that the patient can breathe, a breathing tube needs to be inserted, a process called intubation. Artificial respiration would then be required.

American neurologists published a case report of a healthy man who consulted a chiropractor for his neck pain. Predictably, the chiropractor employed cervical manipulation to treat this condition. The result was bilateral diaphragmatic paralysis.

Similar cases have been reported previously, for instance, here and here and here and here. Damage to other nerves has also been documented to be a possible complication of spinal manipulation, for instance, here and here.

The authors of this new case report conclude that physicians must be aware of this complication and should be cautious when recommending spinal manipulation for the treatment of neck pain, especially in the presence of preexisting degenerative disease of the cervical spine.

I know what my chiropractic friends will respond to this post:

  • I am alarmist,
  • I cherry-pick articles that are negative for their profession,
  • these cases are extreme rarities,
  • conventional medicine is much more dangerous.

To this I reply: Imagine a conventional therapy about which the current Cochrane review says that it has no proven effect for the condition in question. Imagine further that this therapy causes mild to moderate adverse effects in about 50% of all patients in addition to very dramatic complications which are probably rare but, as no monitoring system exists, of unknown frequency. Imagine now that the professionals using this treatment more regularly than any other clinicians steadfastly deny that the risk/benefit balance is way out of kilter.

Would you call someone who repeatedly tries to warn the public of this situation ‘alarmist’?

Would you not consider the professionals who continue to practice the therapy in question to be irresponsible?

Multivitamins are widely used, mainly for disease prevention, and particularly cardiovascular disease (CVD). But there are only few prospective studies investigating their association with both long- and short-term risk. In view of these facts, new evidence is more than welcome.

The objective of this study was to investigate how multivitamin use is associated with the long- and short-term risk of CVD. A prospective cohort study was conducted of 37,193 women from the Women’s Health Study aged ≥45 y and free of CVD and cancer at baseline who were followed for an average of 16.2 y. At baseline, women self-reported a wide range of lifestyle, clinical, and dietary factors. Women were categorized into 1) no current use and 2) current use of multivitamins. Duration and updated measures over the course of the follow-up to address short-term effects were also considered. Women were followed for major CVD events, including myocardial infarction (MI), stroke, and CVD death.

During the follow-up, 1493 incident cases of CVD [defined as myocardial infarction (MI), stroke, and CVD death] occurred. In multivariable analyses, multivitamin use compared with no use was not associated with major CVD event, stroke, or CVD death. A non-significant inverse association was observed between baseline multivitamin use and major CVD events among women aged ≥70 y (P-interaction = 0.04) and those consuming <3 servings/d of fruit and vegetables (P-interaction = 0.01). When updating information on multivitamin use during the course of follow-up, no associations were observed for major CVD events, MI, stroke, and CVD death.

The authors concluded that, in this study of middle-aged and elderly women, neither baseline nor time-varying multivitamin use was associated with the long-term risk of major CVD events, MI, stroke, cardiac revascularizations, or CVD death. Additional studies are needed to clarify the role of multivitamins on CVD.

Even the most enthusiastic vitamin fan will find it hard to argue with these findings; they seem rock solid. Vitamins have their name from the fact that they are vital for our survival – we all need them. But, in developed countries, we all get them through our daily food. Any excess of water-soluble vitamins is swiftly excreted via the urine. Any excess of fat-soluble vitamins is stored in the body and may, in some cases, even represent a health risk.

Exceptions are vulnerable groups such as children, the elderly, pregnant women and patients with certain diseases. These individuals can suffer from hypovitaminoses, the only reason for regularly using vitamin supplements. But for the vast majority of the population, the only effects of regular vitamin supplementation are that we enrich the manufacturers and render our urine expensive.

In the past, I have been involved in several court cases where patients had complained about mistreatment by charlatans. Similarly I have acted as an expert witness for the General Medical Council in similar circumstances.

So, it is true, quacks are sometimes being held to account by their victims. But, generally speaking, patients seem to complain very rarely when they fall in the hands of even the most incompetent of quacks.

Here is one telling reminder showing how long it can take until a complaint is finally filed.

Dr Julian Kenyon is, according to his websitean integrated medicine physician and Medical Director of the Dove Clinic for Integrated Medicine, Winchester and London. Dr Julian Kenyon is Founder-Chairman of the British Medical Acupuncture Society in 1980 and Co-Founder of the Centre for the Study of Complementary Medicine in Southampton and London where he worked for many years before starting The Dove Clinic in 2000. He is also Founder/President of the British Society for Integrated Medicine and is an established authority in the field of complementary treatment approaches for a wide range of medical conditions. He has written approximately 20 books and has had many academic papers published in peer review journals* and has several patents to his name. He graduated from the University of Liverpool with a Bachelor of Medicine and Surgery and subsequently with a research degree, Doctor of Medicine. In 1972, he was appointed a Primary Fellow of the Royal College of Surgeons, Edinburgh.

*[I found only 4 on Medline]

Kenyon has been on sceptics’ radar for a very long time. For instance, he is one of the few UK doctors who use ‘LIVE BLOOD ANALYSIS’, a bogus diagnostic method that can harm patients through false-negative or false-positive diagnoses. A 2003 undercover investigation for BBC 1 South’s ‘Inside Out’ accused Dr Julian Kenyon of using yet another spurious diagnostic test at his clinic near Winchester. Kenyon has, for many years, been working together with George Lewith, another of the country’s ‘leading’ complementary doctors. In 1994, the two published an article about their co-operation; here is its abstract:

This paper outlines the main research effort that has taken place within the Centre for the Study of Complementary Medicine over the last 10 years. It demonstrates the Centre’s expertise and interest in a whole variety of areas, including the social implications and development of complementary medicine, clinical trial methodology, the evaluation of complementary medical machinery, the effects of electromagnetic fields on health and the investigation of the subtle energetic processes involved in complementary medicine. Our future plans are outlined.

Lewith and Kenyon have been using a technique called electrodermal testing for more than 20 years. Considering the fact that the two doctors authored a BMJ paper which concluded that electrodermal machines couldn’t detect environmental allergies, this seems more than a little surprising.

Using secret filming, ‘Inside Out’ showed Dr Kenyon testing a six-year-old boy and then deciding that he is sensitive to dust mites. Later, Dr Kenyon insists that he made his diagnosis purely on the boy’s symptoms and that he didn’t use the machine to test for dust mites. The BBC then took the boy for a conventional skin prick test, which suggested he didn’t have any allergies at all. But Dr Kenyon then says the conventional test may not be accurate: “He may be one of the 10% who actually are negative to the skin tests but benefit from measures to reduce dust mite exposure.”

Despite this very public disclosure, Kenyon was able to practice unrestrictedly for many years.

In December 2014, it was reported in the Hampshire Chronicle that Dr Kenyon eventually did, after a complaint from a patient, end up in front of the General Medical Council’s conduct tribunal. The panel heard that, after a 20-minute consultation, which cost £300, Dr Kenyon told one terminally-ill man with late-stage cancer: “I am not claiming we can cure you, but there is a strong possibility that we would be able to increase your median survival time with the relatively low-risk approaches described here.” He also made bold statements about the treatment’s supposed benefits to an undercover reporter who posed as the husband of a woman with breast cancer.

After considering the full details of the case, Ben Fitzgerald, for the General Medical Council, had called for Dr Kenyon to be suspended, but the panel’s chairman Dr Surendra Kumar said Dr Kenyon’s misconduct was not serious enough to warrant a ban. The panel eventually imposed restrictions on Kenyon’s licence lasting for 12 months.

I estimate that patients are exposed to quackery from doctors and alternative practitioners thousands of times every day. Why then, I ask myself, do so few of them complain? Here are some of the possible answers to this important question:

  • They do not dare to.
  • They feel embarrassed.
  • They don’t know how to.
  • They cannot be bothered and fear the agro.
  • They fail to identify quackery and fall for the nonsense they are being told.
  • They even might perceive benefit from treatments which, in fact, are pure quackery.

Whatever the reasons, I think it is regrettable that not far more quacks are held to account – regardless of whether the charlatan in question as studied medicine or not. If you disagree, consider this: not filing a complaint means that many more patients will be put at risk.

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.

My message to (chiropractic) researchers is simple: PLEASE REMEMBER THAT SCIENCE IS NOT A TOOL FOR CONFIRMING BUT FOR TESTING HYPOTHESES.

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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