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…)
Typical example of a Vitamin K supplement.
Science is complicated. Simple concepts that appear at first to be obviously true or untrue usually turn out to be more nuanced than we thought. Newtonian physics was taken as “the truth” until we learned in the 20th century that it didn’t apply on cosmological or subatomic scales. Medicine and human physiology are more complicated than most people realize or want to believe. A case in point is the recent realization that vitamin K is not a single chemical compound, but a whole family of them, and that vitamin K2 has unique properties that vitamin K1 lacks.
Recently, there has been some interesting preclinical research on K2 that warrants further study to tease out its implications for human health, diet, and supplementation. There has also been a lot of hype that warrants taking its claims not with a grain but with a large bolus of salt. According to Canadian naturopath Kate Rhéaume-Bleue, author of Vitamin K2 and the Calcium Paradox:
- It could save your life
- It is missing from the modern diet
- It is the most important anti-aging nutrient for fighting wrinkles, Alzheimer’s, heart disease, osteoporosis and more
- It promotes straight, cavity-free teeth
- It is needed to get the benefits from calcium and vitamin D supplements; without it, those nutrients will increase the risk of heart attack and stroke
- It is the only vitamin known to prevent and reverse atherosclerosis
The old adage is still true: if something sounds too good to be true, it probably is. There is only weak evidence behind these strong claims. (more…)
In writing about science-based medicine, we give a lot of attention to medicine that is not based on good science. We use bad examples to show why science is important and how it is frequently misapplied, misinterpreted, misreported, or even wholly rejected. It’s a pleasure, for a change, to write about a straightforward example of the best of science-based medicine in action. The book Heart 411 is such an example.
The medical literature is a jungle of conflicting and complicated studies. It’s difficult for novices and even for sophisticated non-specialists to navigate. It’s useful to have experts as guides who can apply their knowledge, experience, and judgment to analyze the data and put everything into perspective. I can’t imagine anyone more qualified as guides to “matters of the heart” than the authors of this book. Heart surgeon Marc Gillinov and cardiologist Steven Nissen practice at the Cleveland Clinic, which has been ranked as the number one heart hospital by U.S. News & World Report for the last 15 years and is currently ranked 4th best hospital overall. They have treated more than 10,000 heart patients over 30 years of clinical practice and have also done extensive research and published hundreds of articles in peer reviewed journals. Their book contains everything they would like their patients to know about the prevention, diagnosis, and treatment of heart disease. It amounts to an owner’s manual for the heart. (more…)
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.
In May 2008, the article “Why the NIH Trial to Assess Chelation Therapy (TACT) Should Be Abandoned” was published online in the Medscape Journal of Medicine. The authors included two of our own SBM bloggers, Kimball Atwood and Wallace Sampson, along with Elizabeth Woeckner and Robert Baratz. It showed that the existing evidence on treating heart disease with IV chelation did not justify further study, and that the TACT trial was questionable on several ethical points. Their ethical concerns were taken seriously enough that enrollment in the trial was put on hold pending an investigation. It has now been re-opened after a few band-aids were applied to the ethical concerns. The scientific concerns were never addressed.
I have seen many critiques of the Atwood study, and not a single one has offered any cogent criticism of its factual content or reasoning. Most of them could have been written by someone who had not bothered to read beyond the title. Their arguments can be boiled down to a few puerile points that can be further simplified to:
(1) I believe the testimonial evidence that chelation works.
(2) Atwood and his co-authors are bad guys.
Now Beth Clay has chimed in with an article entitled “Study of Chelation Therapy Should Not Be Abandoned.” I found it truly painful to read, but even the worst has some value as a bad example. Clay’s article could be used for a game of “Count the Errors.” I will point out some of them below. (more…)
Three kids on the same block were diagnosed with leukemia last year. That couldn’t happen just by chance, could it? There MUST be something in the environment that caused it (power lines, the chemical plant down the street, asbestos in their school, iPods, Twinkies?). Quick, let’s measure everything we can think of and compare exposures to other blocks and find an explanation.
That may be the common reaction, and it may seem plausible to the general public, but it’s not good science.
I have just read a book that does a great job of elucidating the pitfalls of epidemiologic studies, the problematic interface between science and emotion-laden public concerns, and the way environmental hazards have been hyped far beyond the evidence. Hyping Health Risks: Environmental Hazards in Daily Life and the Science of Epidemiology by Geoffrey C. Kabat.
He covers the uses, strengths and limitations of epidemiology, discusses the pros and cons of different study designs, and explains how to judge whether an association is causal.
One of our readers asked that we evaluate a book I had not previously heard of: The China Study: Startling Implications for Diet, Weight Loss and Long-Term Health, by nutrition researcher T. Colin Campbell, PhD, with his non-scientist son Thomas M. Campbell II. The China Study was an epidemiologic survey of diet and health conducted in villages throughout China and is touted as “the most comprehensive study of nutrition ever conducted.” The book’s major thesis is that we could prevent or cure most disease (heart disease, cancer, diabetes, autoimmune diseases, bone, kidney, eye and other diseases) by eating a whole foods plant-based diet, drastically reducing our protein intake, and avoiding meat and dairy products entirely.
Opinions of the book
There’s a lot of praise for this book on the Internet. It was named VegNews Book of the Year. PETA loves it (not surprisingly). Heather Mills McCartney calls it inspirational. It was featured on Oprah.com and endorsed by two of her favorite doctors: Mehmet Oz and Dean Ornish. Its author was even interviewed on Coast to Coast AM.
But I also found this critical review which makes some excellent points and accuses the authors of misrepresenting the findings of the study. And this commenter on an Amazon.com forum also charges Campbell with misrepresenting the data from the study and points out numerous flaws in his reasoning.
I didn’t look at the praise or criticism of others until after I read the book, and the following represents my independent impressions. I approached the book as I do any book with scientific references: I read until I come across a statement of fact that strikes me as questionable and then I check the references given for the statement. This immediately got me off on the wrong foot with this book. In the first chapter I found the statement:
Heart disease can be prevented and even reversed by a healthy diet. (more…)
I’m really tired of arguing about cholesterol, but I feel obliged to stand up once more to defend science-based medicine from unfair calumny.
Lewis Jones’s article “Cholesterol-shmesterol” in Skeptical Briefs (December 2007) included errors and misconceptions about cholesterol. It was a re-hash of the same kind of misinformation that is being spread by The International Network of Cholesterol Skeptics (THINCS) and that I addressed in an earlier post. THINCS would like us to believe that cholesterol has nothing to do with heart disease; that low cholesterol is harmful and high cholesterol is beneficial; and they demonize statins, even falsely claiming that they cause cancer.
I answered Jones with my own article “Cholesterol Clarifications” in the June 2008 issue of Skeptical Briefs. I said I agreed that cholesterol does not “cause” heart disease, that low-fat and low-cholesterol diets have been promoted way beyond the evidence and that statins are being over-prescribed. The public has a lot of misconceptions, but thoughtful science-based doctors agree that the evidence shows: (more…)