…we have at Good Samaritan Hospital a bunch of real smart residents, and a few of them, such as the resident who is on my service, are trained in epidemiology. So I asked Dr (name unpronounceable), my current resident, to explain the article to me or flunk the rotation. So he did an analysis - and part of this is due to persona, and he passes the rotation - but if he wants an A, my card needs some detailing.
So here’s what they did with this study. First they found 818 patients with vertebral artery strokes on the basis of discharge codes. The vertebral artery, by the way, is the one at the base of your neck that feeds the back of your brain.
So the first problem. Discharge coding is not a reliable way to know the real diagnosis. So you don’t really know what they had and more importantly you don’t know the cause of their stroke in this study. I will say that often discharge diagnoses are a best guess which is not often based on the strictest of criteria. But when people compare the real diagnosis to the coded diagnosis they often have a poor correlation. At least in the United states, and this was a Canadian study, reimbursement is an art used to maximise reimbursement
Also, again, note that they have the diagnosis of stroke not the reason for the stroke. And just so you know, for the elderly the most common cause of stroke is embolic events flipping little bits of clot to your brain. In the young it is more common to have a tear in the vertebral artery as a cause of a posterior stroke. This tear in the artery – a dissection – is often the cause of stroke in young people and can be precipitated by trauma. And I would bet that the diagnosis is probably better in younger people than it is in older people with stroke in that younger people tend to get the million dollar work up as they’re not supposed to have a stroke whereas if you have an obese elderly hypertensive smoking diabetic with a stroke – well, you know he might not get the precise diagnosis because – well, strokes happen in that population.
Also of note is that 818 vertebral artery strokes were caused in 100 million patient years in this study so the stroke is not a common thing. This is important in that if you have a high background for vertebral basilar artery strokes with emboli, which is a common cause with the elderly, you will lose the rare dissection as a cause. If you want to find a rare event like a dissection as a cause of stroke, the elderly may not be the best place to look for it as the noise from the embolic strokes will overwhelm any effects from the rare dissection. In the elderly looking for dissection based on stroke codes would be like looking for your cell phone at a concert hall by calling it while The Who is playing. (OK, The Who, I know they’re old, but they did once get the record for the world’s loudest band. My son says Motorhead is louder – I don’t know, for me the archetypal loud band is The Who. Let me know what the world’s loudest band is currently, if you have a moment.)
So, they compared 818 strokes to a control group in the case control study. Now, case control studies are good for a rare disease in a common exposure and can only establish an association which is not, I always emphasise this, the same as establishing causation. They compared those that visited a chiropractor with those that visited a family practitioner over a months’ time to see if it was associated with a vertebral artery stroke and here’s the conclusion from the abstract:
“VBA stroke is a very rare event in the population. The increased risk of VBA stroke is associated with chiropractic and PCP 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 with chiropractic care compared to primary care.”
So that’s the conclusion in the abstract. Is this supported by the paper? Did anybody actually read beyond the abstract? Usually not. That’s one of the reasons it takes so long to prepare these podcasts. You have to read every word over and over again and think about them and that takes time. So does the body of the paper support the conclusions in the abstract? Well, yes or no?
For patients over 45 there was the same association of vertebral artery stroke after a visit to a chiropractor or family care practitioner. Now a stroke mind you – the cause of the stroke was not determined. It would be reasonable to assume that most of the strokes in the elderly group were due to embolic and that the rare event from a dissection, the worry of chiropractic manipulation of the neck where you tear the artery, might not be diagnosed - and that assumes that the patient would volunteer the visit to the chiropractor. It has been my experience that patients who have had a post chiropractic stroke do not volunteer their visit or their manipulation, and you have to ask a direct question. Patients often do not volunteer visits to quacks in general. It’s sort of like confessing that you listen to Michael Bolton or Celine Dion. Some things are just too embarrassing to admit. (Oh, by the way, for the record I listen to neither – yeah right.) But in the over 45 age group strokes due to a chiropractor could be lost in the sea due to strokes from other reasons. In (inaudible word, might be ‘Spine’) we do not know if there was a dissection or emboli as a cause of strokes - it’s hard to conclude that there were no extra strokes from chiropractic. The study was not powered to discover the rare event of a chiropractic event against the background of usual strokes in the elderly. I mean, the mean age in this study was 63.
Elderly – crap. I’m 51 and now I’m calling those in their fifties elderly – damn it, but then I do have my ARUP card so I can get cranky any time I want for any reason I want. Damn kids with their tattoos and visible underwear, goatees and (inaudible word). In my day…in my day it was the day of the hippy so I suppose I really don’t have anything to complain about. Pop culture of my youth is far worse than the pop culture of today) But anyway, young people should not have a stroke.
In the young, vertebral artery dissection is a common cause of a very rare event. It’s also, again, the worry from chiropractic neck manipulation – a modified form of hanging. Remember, if done right, hanging doesn’t choke you – the short fall and sudden stop is supposed to break your neck and if they relax people, as they often do in the chiropractic office, you’re more likely to have trauma than if they were tense and ready for the quick neck snap. You know in the movies they always show you someone breaking someone’s neck to kill them – I think Rambo does that. I wonder if Rambo went to a chiropractor to learn how to do that? Anyway if you could find an adverse effect from chiropractic the place to look would be in the young – and they do.
In the people who had an increased risk of stroke were those under the age of 45. It was a big association. The odds ratios were anywhere from 3 to 12 and the effect was most noticeable in the first 24 hours after seeing a chiropractor. Now, usually if you rip an artery you are symptomatic right away. Again, we do not know if these patients had a dissection or not, we only know that they had a stroke of some sort very shortly after seeing a chiropractor. But if you were to predict that there was an association between chiropractic and stroke, you would most easily find it in the young and the effect would be most noticeable in the first day after a chiropractic visit, because the young should not be having strokes, so a rare event would show up and if you tear an artery you’re going to get symptomatic right away. And this article strongly confirms that association.
Now note the word ‘association’. Association is not causation. If you want to prove causation you would need a prospective study comparing stroke rates from patients who saw chiropractors versus those who did not visit chiropractors – if you want to find causality. But if you are less than 45 and you visit a chiropractor, there is strong association between that visit and a stroke in the next 24 hours.
There is a table in the article that has the smoking gun. You gotta read it carefully, but the highest odds ratio for a stroke is 12 – four times that of any other odds ratio and it occurs in age less than 45 in the first 24 hours after a visit to a chiropractor. Part of what they do in the study, by the way, is kind of smear out the data by looking at stroke for a month after a chiropractic visit and diluting the effect of it the first 24 hours after the visit. Now how do the authors deal with this data? They emphasise in the abstract – which is all anyone seems to read – is there’s equal stroke after a visit to a chiropractor and primary care physicians – and their abstract, although they do mention it in the meat of their article, they do not bother to mention that there is an increased association in the young. You gotta read the discussion which most people do not read. They account for this by suggesting that patients with headache and neck pain – symptoms of an incipient vertebral artery stroke – lead people to seek care from their DC or their MD. In other words they had a stroke in progress at the time they sought care. This is kind of like saying after a hanging, “yes, the neck is broken – but it occurred on the steps on the way up to the scaffold”. Now listen carefully for those of you who sent me this article…
This is the hypothesis that they came up with to account for the data. This is spin. Most of this authors of this paper were D-d-d-doctors (there I said it and my tongue did not cleave from the roof of my mouth) of Chiropractic – DCs. So they spun this article as best they could. But this hypothesis may be true – but it was not the design of this study to show this and it is not proven by the data since they have no clue as to why patients were visiting their doctors. The study was not designed to show that result. It’s a hypothesis from the study.
People who do not read the article carefully take this hypothesis – and they call it a hypothesis in the paper as a conclusion of the data: The patients had symptoms before they sought care and their stroke was pre-existing - that it occurred before the visit is not proven by this study and the study is not designed to show this. It will take another study to prove this hypothesis.
My read of the paper is different. My spin is that the paper confirms that a population that should not be having a stroke – the young – has an increase risk association of having a stroke after visiting a chiropractor and, given the rarity of VBA dissection, the elderly is not a group where one could easily find a stroke after a chiropractic visit. To quote the paper:
“We have not ruled out neck manipulation as a potential cause of VBA strokes. On the other hand [Mark Crislip: “Now get this…”] it is unlikely to be a major cause of these rare events. Our results suggest that the association between chiropractic care and VBA stroke found in previous studies is likely explained by the presenting symptoms attributable to vertebral artery dissection.”
Note the word “major”. I agree that chiropractic is not a major cause of stroke – at least in the elderly. In the young, your highest odds ratio – or to have a stroke in the first 24 hours after visiting a chiropractor – given the number of chiropractic visits and the rarity of a VBA tear – I agree, chiropractic is probably a rare cause of a rare event.
However, to have a stroke after the application of magical nonsense is one stroke too many. Now go to the website whatstheharm.com and peruse the chiropractic section. It is striking how many people had a stroke who were young, who’d just had chiropractic neck manipulation. Of course, these are just anecdotes and the plural of anecdotes is anecdotes, not data – but wait – anecdotes are the prime proof of alt-med proponents since evidence usually proves their pet quackery is a crock. To reframe as Dr Wild would, these strokes are “uncontrolled clinical observations” – not anecdotal evidence and should have the same weight as clinical trials. Why do I feel that proponents of modified hanging – I mean neck adjustment – will ignore these anecdotes and give credence to those anecdotes that show benefit?
But given the two studies now that show an increase in stroke rates in the young after neck manipulation, I would not let a chiropractor anywhere near my neck.
Here’s also a difference between scams and real medicine: In real medicine it takes much less data than this to bring a drug under scrutiny and decide if the benefits are worth the potential risks of therapy. In my own world of infectious diseases there have been millions of doses of the antibiotic Talithromycin - brand name Ketek - given and only a handful of patients who have had liver failure and death from this antibiotic. I would never give this antibiotic to anybody unless I had no other options given that the potential risks, be that very small, are in fact potentially fatal – and this is for a therapy that actually works. I can’t believe that giving a therapy that doesn’t work that causes a stroke would be allowed by anybody.
Sandra Nette, who had neck manipulation by a chiropractor up in Canada, and a brainstem stroke and is now locked-in – she can only move her eyes – is suing not only the chiropractor, but the Canadian government for $500,000 million.
She is suing the government as they supported chiropractic nonsense. She was 40 at the time. And I sure hope that her lawyers find this article and read it. It supports the contention that chiropractic causes stroke – I mean, sorry – chiropractic is associated with stroke
Do I think that this study confirms that chiropractic causes stroke? You betcha. It is a form of modified hanging and is dangerous without adding benefit.
