A new review published in the BMJ once again opens the question of the risks vs benefits of daily aspirin as a prevention for heart attacks and strokes. The reviewers looked at nine randomized trials involving over 100,000 patients and found that aspirin is effective in reducing heart attacks and strokes, but also increases the risk of gastrointestinal bleeding and that in some patients this risk outweighs the benefit.
This is an old and enduring controversy, and one with significant public health ramifications. Aspirin is an anti-platelet agent – it inhibits platelets, the cell fragments in the blood that are the first line against bleeding, from aggregating (clumping together). Platelets aggregate in order to quickly stop bleeding from damaged veins or arteries. But they can also aggregate around cholesterol plaques in arteries, causing a large thrombus (blood clot) that can block off the artery, or that can break off and lodge in a downstream artery (an embolus) and cause a stroke or heart attack.
By inhibiting platelet aggregation daily aspirin reduces the risk of forming a thrombus or embolus, and thereby reduces the risk of heart attack or stroke. Of course, the real story is always more complex than our straightforward explanations. There is some research to suggest that the anti-inflammatory effects of aspirin may also be important to their role in reducing vascular risk. The relative contribution of anti-platelet and anti-inflammatory effects have not been fully teased out. Further, the anti-inflammatory effects of daily aspirin may have non-vascular benefits, like reducing the risk of some cancers.
One of the recurrent themes of science-based medicine is that any medical intervention that can plausibly cause physiological benefit can also plausibly cause physiological harm. There is no such thing as “it can’t hurt.” Sometimes the risk may be minuscule – but we should never assume that it is zero. Being “natural” or “holistic” or being blessed with some other alleged marketable virtue does not affect the risk vs benefit calculation of an intervention.
Vitamins are an excellent example. There is widespread sentiment that vitamins are harmless, and that supplementing with vitamins is therefore a no risk-possible benefit scenario. It is certainly reasonable to conclude from the evidence that vitamins (at usual supplemental levels) are low risk, compared to many other types of medical interventions. High doses, or megadoses, of vitamins, however, risk toxicity and this risk increases with the dose.
But even at sub-toxic doses vitamins should not be assumed to be risk free. This is especially true when we take a public health perspective – what is the net effect of large scale supplementation on the population? A new meta-analysis looking at the net effects of Vitamin E supplementation on stroke risk reinforces this caution.
While manipulation of any kind has the potential to cause injury, stroke caused by neck manipulation is of greatest concern. Risk must always be weighed against benefit when upper neck manipulation is considered. Risk of stroke caused by neck manipulation is statistically low, but the risk is serious enough to outweigh benefit in all but a few rare, carefully selected cases.
When the RAND (Research and Development) organization published its review of the literature on cervical spine manipulation and mobilization in 1996, it concluded that only about 11.1% of reported indications for cervical spine manipulation were appropriate and that stroke and other serious complications occurred about 1.46 times per one million neck manipulations.1 In the same year, after examining 183 cases of vertebrobasilar stroke that occurred from 1934 through 1994 following neck manipulation, the National Chiropractic Mutual Insurance Company (NCMIC) concluded that “It has to be accepted that VBS [vertebrobasilar stroke] following SMT [spinal manipulative therapy] does occur.”2
There is a very good chance that you will feel worse after seeing a chiropractor.
According to a new systematic review, serious complications of spinal manipulation are rare, but 33-60% of patients experience milder short-term adverse effects such as increased pain, radiation of pain, headaches, vertigo and even loss of consciousness. The study, published in the journal Spine, involved searching PubMed and the Cochrane Library for the years 1966 to 2007. They identified additional studies by hand searching. They looked for all articles that reported adverse effects associated with chiropractic irrespective of type of design. They omitted any reports where patients had underlying diseases (osteogenesis imperfecta, expansive vertebral hemangioma, osteoporotic fracture, etc.) that predisposed them to complications with manipulation.
They found 46 pertinent studies:
- One randomized controlled trial
- Two case-control studies
- Six prospective studies
- Twelve surveys
- Three retrospective studies
- 115 case reports
They recognized that “the heterogeneity of the study designs did not allow conducting a formal meta-analysis.” But they did the best they could to make sense out of what they found. (more…)
The chiropractic industry must be feeling the pressure. Billboards, signs on the sides of buses, chiropractic victims’ organizations, and lawsuits are telling the world that chiropractic neck adjustments can cause strokes. The risk is very small, but it is very real. We have addressed the subject before on this blog here, here, and here.
Chiropractors are in denial and are trying to shift the blame elsewhere. A correspondent sent me copies of a pamphlet and a “distribution kit” that the FCER (Foundation for Chiropractic Education and Research) is selling to chiropractors so they can inform the public about cervical artery dissection (CAD). It is advertised as a campaign to help the public recognize warning signs of stroke; but in my opinion, it amounts to a cynical, self-serving ploy to divert attention away from neck manipulation and to spread biased information about the recent study in Spine by Cassidy et al. (more…)
Over 26 million Americans are taking statin drugs. Some people think they should be available over-the-counter without a prescription, and it has even been facetiously suggested that they should be added to our drinking water. The protective effect of statins in cardiovascular disease and in high-risk patients with high cholesterol levels is well established. But what about people with no heart disease and normal cholesterol levels – can they benefit too?
The New England Journal of Medicine has pre-released an important new study on statins online prior to its planned publication date of November 20, 2008. It is certain to stir up a lot of controversy, and the International Network of Cholesterol Skeptics will not be happy, because it contradicts some of their favorite arguments. They have claimed that statins do more harm than good, that reducing cholesterol levels is harmful to health, that the benefits of statins and/or cholesterol lowering do not extend to women and the elderly, and that studies showing benefits of statins are meaningless because they do not show reduction of overall mortality. This study indicates otherwise. (more…)
Sandra Nette is a prisoner, condemned to spend the rest of her life in the cruelest form of solitary confinement. Her intact mind is trapped in a paralyzed body and she is unable to speak. She can move one arm just enough to type on a special keyboard. She cannot swallow or breathe on her own, and must be frequently suctioned. She feels sensations and is in pain. Her condition is known as “locked-in syndrome” and has been described as “the closest thing to being buried alive.” She is suing those responsible for her cruel fate and I hope she wins.
She was a healthy 40 year old woman who wanted to stay healthy. She did all the right things like watching her weight, eating right, and not smoking. She followed the advice of a chiropractor to include regular maintenance chiropractic adjustments in her health regimen. On September 13, 2007 she had the last adjustment she would ever have.
There was nothing wrong with her. She didn’t see the chiropractor for headaches, neck pain, back pain or any other complaint. She went for a “tune-up” that she thought would help keep her healthy. The chiropractor did a rapid-thrust adjustment on her neck. Right afterwards, she complained of feeling “sore, dizzy and unwell.” She tried to leave but had to sit down. The chiropractor failed to recognize the medical emergency, and instead of calling an ambulance he recommended that she would benefit from purchasing massage therapy from his clinic. He let her leave the office and drive home alone. She only made it part way. (more…)
A long time ago I read a study about what makes a good doctor. Some things you might think were important, like grades in medical school, were irrelevant. What correlated the best was the number of medical journals a doctor read. I don’t know whether that means good doctors read more journals or reading more journals makes a better doctor.
One thing I do know is that most of us could learn better journal-reading skills. When I was a busy clinician, I did what I suspect many busy clinicians do: I let the journals pile up for a while, then tackled a stack when I got motivated. I would skim the table of contents to pick out articles that I wanted to read, then I would read the abstracts of those articles. If the abstract interested me, I would read the discussion section of the article. If I was still interested, I might go back and read the entire article. But until after I retired, I never really developed the skills to evaluate the quality of the study.
I knew enough not to jump on the bandwagon the first time something was reported, because I had seen promising treatments bite the dust with further testing. But I really wasn’t aware of all the things that can go wrong in a study, and I didn’t know what to look for to decide if the results were really credible. I’m not an academic; I thought the authors knew a lot more than I did, and I trusted them to a degree that was not warranted. (more…)
I wonder how many people have heard that chiropractic neck adjustments can cause strokes. It isn’t exactly common knowledge. One organization is trying to raise public awareness through signs on the side of city buses (Injured by a Chiropractor? Call this number) and through TV commercials. I had never heard about this phenomenon myself until a few years ago, when I heard it mentioned on an episode of Alan Alda’s Scientific American Frontiers. I questioned his accuracy, but I quickly found confirmation in the medical literature.
A typical case was that of 24 year old Kristi Bedenbaugh who saw her chiropractor for sinus headaches. During a neck manipulation she suffered a brain stem stroke and she died three days later. Autopsy revealed that the manipulation had split the inside walls of both of her vertebral arteries, causing the walls to balloon and block the blood supply to the lower part of her brain. Additional studies concluded that blood clots had formed on the days the manipulation took place. The chiropractor later paid a $1000 fine. (more…)
I recently read a fascinating book, The Brain That Changes Itself by Norman Doidge. He describes case histories and research indicating that the brain is far more malleable than we once thought. We used to think each function was localized to a small area of the brain and if you lost that area of brain tissue the function was gone forever. We once thought you couldn’t teach an old dog new tricks. Now we know better.
Learning a new skill actually changes the structure and function of the brain, even into old age. If you exercise one finger, the area of the brain devoted to that finger enlarges. The old concept of dedicated brain areas for specific functions no longer holds. Areas of the cortex that normally process vision can learn to process totally different inputs such as hearing. This is what happens with blind people: their hearing skills are enhanced when new neural connections for hearing invade the disused visual cortex. They may not actually have better hearing acuity, but they have learned to pay more attention to auditory input and to use it to build up a representation of the world around them.
One of the more intriguing experiments he describes was in monkeys. When sensory input nerves to one arm were severed, the monkey stopped using the arm, even though the motor nerves were intact. When the good arm was put in a sling, the monkey started using the impaired arm again. When both arms were deprived of sensory input, the monkey used both arms. (more…)