A new study published in JAMA sheds further light on a controversial question – whether or not to prescribe low-dose aspirin (81-100mg) for the primary prevention of vascular disease (strokes and heart attacks).
Primary prevention means preventing a negative medical outcome prior to the onset of disease, in this case preventing the first heart attack or stroke. Secondary prevention refers to treatments given to patients who have already had their first heart attack or stroke in order to reduce the risk of subsequent events.
The evidence strongly supports the efficacy of aspirin for the secondary prevention of both heart attacks and strokes. Aspirin has two effects which likely contribute to this protective effect. First, aspirin is an anti-platelet agent – it reduces the stickiness of platelets, which are cell fragments in the blood that clump together to stop bleeding. They can also clump together around an ulcerated cholesterol plaque on an artery, forming a thrombus, resulting in blockage or embolus (the clot traveling downstream) and causing either a heart attack or stroke.
Other anti-platelet agents, such as clopidogrel, are also effective in preventing stroke and heart attack.
Of course, platelets exist for a reason, and blocking their action increases the risk of bleeding or can make bleeding worse when it occurs. Therefore determining the optimal dose and target population are important to maximize the benefit of aspirin or other anti-platelet agent while minimizing the bleeding risk. (more…)
Case reports are perhaps the weakest form of medical evidence. They are essentially well-documented anecdotes. They do serve a useful purpose, however. They can illuminate possible correlations, the natural course of illness and treatment, and serve as cautionary tales regarding possible mistakes, risks and complications. I say “possible” because they are useful mainly for generating hypotheses and not testing or confirming hypotheses.
Dramatic case reports, however, with objective outcomes, like death, can be very useful by themselves in pointing out a potential risk that should be avoided. For example, case reports of objective and severe adverse outcomes are often used as sufficient evidence for pulling approved drugs off the market, or at least adding black box warnings.
The chiropractic community, it seems, does not respond in a similar way to dramatic adverse events that suggest possible risk from chiropractic manipulation. A recent and unfortunate case raises once again the specter of stroke following chiropractic neck manipulation. Jeremy Youngblood was 30 years old, completely healthy, and saw his chiropractic for some neck pain. According to news reports, Jeremy suffered a stroke in his chiropractor’s office while being treated with neck manipulation for the neck pain. According to reports the chiropractor did not call 911, but instead called Jeremy’s father who had to come and pick him up and then bring him to the ER. Jeremy suffered from a major stroke and later died.
On the home page of Zhu’s Neuro-Acupuncture Center there is a video relaying a testimonial of how scalp acupuncture helped a patient recover from acute stroke. The use of testimonials is very common in the promotion of dubious health treatments. A personal story and endorsement is psychologically more compelling than dry data. Testimonials are completely unreliable, however, and in fact I would argue that they are ethically questionable. I would even go as far as saying that the presence of testimonials is almost a sure sign that the treatment being promoted is not legitimate.
Webpage screenshot (click picture to embiggen)
What I could not find on Zhu’s website were links to published scientific researcher establishing the safety and efficacy of his treatments. You would think if they existed, he would display them prominently.
Acupuncture for stroke is a common claim, contradicting the notion that acupuncture is primarily used for the symptomatic treatment of subjective symptoms. That, in my experience, is part of the promotional strategy for many CAM treatments. They are presented as benign treatments for symptomatic treatment only, so what’s the possible harm. In reality, proponents will claim they can actually treat diseases whenever given the chance.
Chiropractors often deny that neck manipulation can be a primary cause of stroke by injuring vertebral arteries. But according to Jean-Yves Maigne, M.D., head of the Department of Physical Medicine at the Hôtel-Dieu Hospital in Paris, France:
It is now a well established fact that cervical thrust manipulation can harm the vertebral artery. This accident was formerly regarded as very rare, although severe, and related to atherosclerosis. Clinical tests were proposed to detect patients at risk. The problem is now better known. It is no longer attributed to atherosclerosis…but to a dissection of a vertebral artery, a clinical entity observed in younger patients (20-45 years). It remains very rare, but mild symptoms appear to be not so infrequent. Finally, the predicting tests seem to be deprived of any value.1
In 1997, the French Society of Orthopaedic and Osteopathic Manual Medicine (SOFMMOO), following presentations by anatomists, neurologists, radiologists, and practitioners in the field of French Manual Medicine, adopted the neck-manipulation proposals made by Dr. Maigne.1 “Acknowledging the fact that prevention is out of reach,” said Dr. Maigne, “the aim of these recommendations is to reduce the number of (not to say to suppress) rotational cervical thrust manipulations in a targeted population. This population consists mainly in females of less than 50 years old. Five recommendations were developed, in addition to classic contraindications of spinal manipulative therapy.”
The recommendations of the SOFMMOO, dealing with cervical manipulation in general and allowing the use of neck manipulation in special cases, are worth considering since they were reviewed by medical specialists in different disciplines and approved by licensed practitioners who use manual therapy, long before the stroke-neck-manipulation furor reached its peak in the United States.
You may have noticed that men and women are different. I hope you have noticed. As the French say, vive la différence! It’s not just that one has dangly bits and the other has bumpy chests. Or that one has to shave a beard and doesn’t like to ask for directions while the other has menstrual periods and likes to discuss feelings. There are differences in physiology and in the incidence of various diseases. For instance, normal lab values for hemoglobin are higher for men than for women, and autism is more prevalent in males while multiple sclerosis is more prevalent in females.
In the past, women have been underrepresented in clinical studies; when the first studies of aspirin for cardiovascular prevention came out, we knew it was effective for men, but we didn’t have enough evidence to recommend it for women. This is changing; researchers today are more aware of the need to include women in their studies. Now the American Heart Association/American Stroke Association (AHA/ASA) has issued the first evidence-based guidelines for reducing the risk of stroke in women. (more…)
A Swedish researcher, Staffan Lindeberg, has been studying the inhabitants of Kitava, one of the Trobriand Islands of Papua New Guinea. He claims that sudden cardiac death, stroke, and exertion-related chest pain never occur in Kitava; and he attributes this to their eating a Paleolithic diet.
2,250 people live on Kitava. They are traditional farmers. Their dietary staples are tubers (yam, sweet potato and taro), fruit, fish, and coconut. They don’t use dairy products, alcohol, coffee, or tea. Their intake of oils, margarine, cereals, and sugar is negligible. Western foods constitute less than 1% of their diet. Their activity level is only slightly higher than in Western populations. 80% of them smoke daily and an unspecified number of them chew betel. The macronutrient composition of the Kitavan diet was estimated as 21% of total calories from fat, 17% from saturated fat, 10% from protein, and 69% from carbohydrates.
Lindeberg’s Kitava study examined a sample of 220 Kitavans aged 14-87 and compared them to healthy Swedish populations. They found substantially lower diastolic blood pressure, body mass index, and triceps skinfold thickness in the Kitavans. Systolic blood pressure was lower in Kitava than in Sweden for men over 20 and women over 60. Total cholesterol, LDL cholesterol, and apolipoprotein B were lower in men over 40 and in women over 60. Triglycerides were higher in Kitavans aged 20-39 than in Swedes of the same age. HDL was not significantly different. (more…)
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