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Archive for Epidemiology

Dental X-rays and Brain Tumors — Oh My!

Fear sells, and the media loves it. If it’s scary, no matter how tenuous the link or inconclusive the study, you are going to see it on the news. How many times over the years have you heard that your cell phone might give you brain cancer, even though it never turns out to be true? Once such a claim is made, however, it becomes lodged into the public’s psyche and is accepted as true, even after refutations and retractions are published (see Wakefield, Andrew).

And so it is with x-rays. The latest scare du jour, a recent study out of Yale that claims to show a correlation between dental x-rays and intracranial meningioma — the most common brain tumor and usually benign — has been enjoying widespread attention in newspapers and on the evening news. We don’t know if it will be on Dr. Oz, because we can’t bring ourselves to watch that show, but we feel the chances are good. Other alt-medders will no doubt have collective woogasms over the story and will further incite fear and mistrust into the doctor-patient relationship. In fact, the Mercola website wasted no time in weighing in:

While this study does not necessarily establish causation between dental X-rays and tumors, previous research has also implicated dental X-rays in the development of thyroid cancer, and research clearly shows this type of radiation is not harmless…

Typical alarmist fear-mongering. When has any health care professional claimed that radiation is harmless? This is not cutting edge research; Wilhelm Röntgen, the discoverer of x-rays in 1895 and winner of the Nobel Prize in 1901 for his research in the field, advocated the use of lead aprons for protection from the ionizing radiation way back when. Further, trying to lump one study linking dental x-rays to meningioma to another study linking them to thyroid cancer is taking quite the kitchen sink approach. But if there are multiple alleged possible potential theoretical adverse effects from our dental death rays, it must be true, right?

Well, not so fast. We’re dentists, and unlike many knee-jerkers, we’ve actually read the study and would like to offer a little bit of insight into this before everyone panics. In fact, with respect to Letterman, we’d like to offer our Top Three Reasons Not To Panic:
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Posted in: Cancer, Dentistry, Epidemiology, Medical Academia, Science and the Media

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Gold mine or dumpster dive? A closer look at adverse event reports

All informed health decisions are based on an evaluation of expected risks and known benefits. Nothing is without risk. Drugs can provide an enormous benefit, but they all have the potential to harm. Whether it’s to guide therapy choices or to ensure patients are aware of the risks of their prescription drugs, I spend a lot of time discussing the potential negative consequences of treatments. It’s part of my dialogue with consumers: You cannot have an effect without the possibility of an adverse effect. And even when used in a science-based way, there is always the possibility of a drug causing either predictable or idiosyncratic harm.

An “adverse event” is an undesirable outcome related to the provision of healthcare. It may be a natural consequence of the underlying illness, or it could be related to a treatment provided. The use of the term “event” is deliberate, as it does not imply a cause: it is simply associated with an intervention. The term “adverse reaction,” or more specifically “adverse drug reaction,” is used where a causal relationship is strongly suspected. Not all adverse events can be be causally linked to health interventions. Consequently, many adverse events associated with drug treatments can only be considered “suspected” adverse drug reactions until more information emerges to suggest the relationship is likely to be true.

Correlation fallacies can be hard to identify, even for health professionals. You take a drug (or, say, are given a vaccine). Soon after, some event occurs. Was the event caused by the treatment? It’s one of the most common questions I receive: ”Does drug ‘X’ cause reaction ‘Y’?” We know correlation doesn’t equal causation. But we can do better than dismissing the relationship as anecdotal, as it could be real. Consider an adverse event that is a believed to be related to drug therapy: (more…)

Posted in: Epidemiology, Pharmaceuticals

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Keeping the customer satisfied

One thing about blogging once a week or so compared to my other blogging gig, which is usually close to every day, occasionally more often, is that I really can’t cover everything I want to cover for this blog. Even more so than at my not-so-super-secret other blogging gig, I have to pass on topics that could be fodder for what could be excellent to even awesome posts—or, self-congratulating hyperbole aside, at least reasonably interesting to the readers of this blog. When that happens, I can only hope that one of my co-bloggers picks up on it and gives the subject matter the treatment it cries out for. Or, sometimes, such subject matter just has to be dealth with elsewhere by me—or not at all. Even a hypercaffeinated blogger like myself has limits.

Sometimes, however, I actually get a second chance. In other words, I get a chance to revisit a topic that I passed by. Usually, this happens when something new happens that gives me an excuse to revisit the topic. So it was last of week, when I was perusing the New York Times by an oncology nurse named Theresa Brown. Her article was titled, appropriately enough, Hospitals Aren’t Hotels. It will become very apparent very quickly why in a moment. But first, let’s sample Brown’s article a bit, because it brings up an issue that is very pertinent to science-based medicine:
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Posted in: Clinical Trials, Diagnostic tests & procedures, Epidemiology

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Mass Media Attention Psychogenic Syndrome – MMAPS

By now you have probably heard of the middle and high school children in LeRoy, NY who have come down with what some reports are calling a “mystery” illness. Of course it is almost obligatory to note in such stories that doctors or experts are “baffled.” There are several features of this story that are interesting from a science-based medicine and also just a critical thinking point of view – the media response, how such ailments are diagnosed, the publicity around a private medical condition, and the speculation from many camps that appears ideologically motivated.

To first review the facts of the case, there are now 15 children affected with involuntary tics, which are sudden “jerk-like” motor movements. They all attend the same junior-senior high school and so range in age from 12-18, with onset of symptoms from October to January of the current school year.  All but one of them are girls. All of the children have been examined by pediatric neurologists, 12 of the 15 at the Dent neurological institute by the same two neurologists, including Dr. Lazlo Mechtler.

Dr. Mechtler, and in fact all of the pediatric neurologists who have examined any of the children, have come to the same diagnosis: conversion disorder and mass psychogenic illness. A conversion disorder occurs when psychological stress manifests as physical symptoms. We take this for granted to some degree – when people feel anxious they may get sweaty, nauseated, short of breath, and have palpitations. People with panic attacks can have these symptoms and also difficulty swallowing, and episodes that may resemble certain types of seizures with feelings of being separate from reality or from themselves. These are physical symptoms resulting from pure emotional stress. But in some cases psychological stress can also lead to neurological symptoms – pretty much any neurological symptoms, such as weakness, difficulty speaking, loss of vision, and involuntary movements.

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Posted in: Epidemiology, Neuroscience/Mental Health

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Et tu, Biomarkers?

Everything you know may be wrong. Well, not really, but reading the research of John Ioannidis does make you wonder. His work, concentrated on research about research, is a popular topic here at SBM.  And that’s because he’s focused on improving the way evidence is brought to bear on decision-making. His most famous papers get to the core of questioning how we know what we know (or what we assume) to be evidence. (more…)

Posted in: Basic Science, Clinical Trials, Diagnostic tests & procedures, Epidemiology, Science and Medicine

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Smallpox and Pseudomedicine

A good case of smallpox may rid the system of more scrofulous, tubercular, syphilitic and other poisons than could otherwise be eliminated in a lifetime. Therefore, smallpox is certainly to be preferred to vaccination. The one means elimination of chronic disease, the other the making of it.

Naturopaths do not believe in artificial immunization . . .

—Harry Riley Spitler, Basic Naturopathy: a textbook (American Naturopathic Association, Inc., 1948). Quoted here.

Here’s what a good case of smallpox will do for you:

If you’re lucky enough to beat the reaper (20-60%; 80% or higher in infants) or blindness (up to 30%), those blisters will leave you scarred for life. Oh, and the next time a good smallpox epidemic comes around, your children born since the last one will catch it and contribute their fair share to the death rate. But not you because you’ll be immune, so you’ll have the “preferred” experience of watching your children die well before you do.

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Posted in: Chiropractic, Epidemiology, Health Fraud, History, Homeopathy, Naturopathy, Public Health, Vaccines

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Vaccines and infant mortality rates: A false relationship promoted by the anti-vaccine movement

The anti-vaccine movement is a frequent topic on the Science-Based Medicine blog. There are a number of reasons for this, not the least of which being that the anti-vaccine movement is one of the most dangerous forms of pseudoscience, a form of quackery that, unlike most forms of quackery, endangers those who do not partake of it by breaking down herd immunity and paving the way for the resurgence of previously vanquished diseases. However, anti-vaccine beliefs share many other aspects with other forms of quackery, including the reliance on testimonials rather than data. Even so, although the intelligentsia (and I do use the term loosely) of the anti-vaccine movement realizes and exploits the power of anecdotes and testimonials and how human beings tend to value such stories over dry scientific data, leaders of the anti-vaccine movement realize that science is overwhelmingly against them and that testimonials alone are not adequate to counter that science in the realm of public policy and relations.

That’s why, over the years, various anti-vaccine “scientists” (and I use that term very loosely as well) have produced poor quality, sometimes even fraudulent studies, which are then touted as evidence that vaccines cause autism or at least as evidence that there is actually still a scientific controversy when in fact from a scientific standpoint the vaccine-autism hypothesis is pining for the fjords. Examples abound, including the work of Mark and David Geier, whose studies led the to use chemical castration to treat autistic children; Andrew Wakefield, whose small case series almost certainly included fraudulent data; a truly incompetent “phone survey” commissioned by Generation Rescue designed to compare “vaxed versus unvaxed” children; and an even more incompetent “study” in which Generation Rescue used a cherry picked group of nations to try to argue that nations that require more vaccines have higher rates of infant mortality. These efforts continue. For example, last year Generation Rescue requested $809,721 from the Airborne settlement to set up a “vaxed versus unvaxed” study, despite the known difficulties with such a study and the low likelihood of finding anything without huge numbers of children.

Last week, they were at it again.
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Posted in: Epidemiology, Vaccines

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The benefits and risks of folic acid supplementation

Could a vitamin with proven benefits in one group cause harm to another? That’s the growing concern with folic acid, the vitamin that dramatically reduces the risk of neural tube birth defects such a spina bifida. Studies designed to explore the possible benefits of folic acid for heart disease, stroke and cancer are giving out some worrying signs: At best, folic acid is ineffective, and at worst it may be increasing the risks of some cancers. So what does this say about routine supplementation for the typical healthy individual, and its overall risk and benefit?

Folate (vitamin B9) is an essential nutrient found green, leafy vegetables, broccoli, peas, corn, oranges, grains, cereals, and meats. Folate has important roles in the synthesis of DNA, and consequently cell division. Significant folate deficiency can lead to macrocytic anemia. Folic acid, a synthetic form of folate, is used in multivitamins supplements because it is better absorbed.

Folic acid’s benefits in pregnancy are well documented. Supplementation before conception, and in the first few weeks of pregnancy, significantly and substantially lower the risk of several different birth defects, including neural tube defects (NTDs). The neural tube is the embryonic precursor to the brain and spinal column. NTDs include very serious defects like spinal bifida and anencephaly, birth without part of the brain.

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Posted in: Clinical Trials, Epidemiology

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Deadly Indeed

There are sources of information I inclined to accept with minimal questioning.  I do not have time to examine everything in excruciating detail, and like most people, use intellectual short cuts to get through the day.  If it comes from Clinical Infectious Diseases or the NEJM, I am inclined to accept the conclusions without a great deal of analysis, especially for non-infectious disease articles.  Infectious disease publications I have to read more closely; its part of passing as an expert.

Outside of medicine, I am predisposed to accepting at face value many of the articles in Skeptic and Skeptical Inquirer. They are trusted sources.  Some topics, like haunted house or Big Foot investigations, I barely skim. After all these years, I doubt there will be any new insights into the subject.  Other topics, depending on my interest, I may read more carefully.

I  often read longer articles  many times.  First a quick skim to see if it offers anything of interest.  If it does, then I may read it carefully.

This months Skeptical Inquirer had an article called  Seven Deadly Medical Hypotheses by Reynold Spector.  Just seeing the title and knowing the magazine, I was primed to accept the content at face value.  I enjoy a well reasoned, thoughtful rant. I relish a clever diatribe, even if I do not agree with the topic.   So I gave it a quick skim.  I was discomfited.  My first gut check was ick.  But I was uncertain why.  So I read it slowly and carefully, and still ick.  But why? (more…)

Posted in: Epidemiology, Science and Medicine, Science and the Media

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Critique of “Risk of Brain Tumors from Wireless Phone Use”

Following my recent critique here of the book Disconnect by Devra Davis, about the purported dangers of cell phones to health, David Gorski asked me to comment on a recently published “review article” on the same subject. The article is entitled “Risk of Brain Tumors from Wireless Phone Use” by Dubey et al [1] published in the J. Comput Assist Tomography. At the outset, the same question occurred to both of us: what is a “review article” about cell phones and brain tumors doing in a highly technical journal dedicated to CT scans and CT imaging? While we are both still guessing about the answer to this question, we agreed that the article itself is a hodge-podge of irrational analysis.

As you might surmise, Dubey and his Indian co-authors come to the conclusion that “that the current standard of exposure to microwave during mobile phone use is not safe for long-term exposure and needs to be revised.” But within the conclusion there is also the following: “There is no credible evidence from the Environmental Health and Safety Office (I presume in India) about the cause of cancer or brain tumors with the use of cell phones. It is illogical to believe that evidence of unusual brain tumors is only because of hundred’s of millions of people using cell phones worldwide.” What?! These are opposite and contradictory statements. The main body of the article includes a lot more instances of such inconsistency.

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Posted in: Clinical Trials, Epidemiology, Science and Medicine

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