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Archive for Epidemiology

Behold the spin! What a new survey of placebo prescribing really tells us

One of the recurring topics here at SBM is the idea of the placebo: What it is, what it isn’t, and how it complicates our evaluation of the scientific evidence. One my earliest lessons after I started following this blog (I was a reader long before I was a writer) was that I didn’t understand placebos well enough to even describe them correctly. Importantly, there is no single “placebo effect”. They are “placebo effects”, a range of variables that can include natural variation in the condition being studied, psychological factors and subjective effects reported by patients, as well as observer bias by researchers studying a condition. All of these, when evaluated in clinical trials, produce non-specific background noise that needs to be removed from the analysis. Consequently, we compare between the active treatment and the placebo to determine if there are an incremental benefits, to which we apply statistical tests to determine the likelihood that the differences between the intervention and the placebo groups are real. Removed from the observational nature of the clinical trial, we can’t expect the observed “placebo effects” to persist, as they’re partially a consequence of the trial itself. A more detailed review of placebos is a post in and of itself, so I’ll refer you to resources that describe why placebo effects are plural, that placebo effects are subjective rather than objective and there is no persuasive evidence to suggest that placebo effects offer any health benefits. What’s most important is the understanding that placebo effects are a measurement artifact, not a therapeutic effect.

Placebo effects are regular topics within in SBM posts because an understanding of placebo effects is essential to evaluating the evidence supporting (so-called) complementary and alternative medicine, or CAM. As better quality research increasingly confirms that the effects from CAM are largely, if not completely, attributable to placebo effects, we’ve seen the promoters of CAM shifting tactics. No longer able to honestly claim that CAM has therapeutic effects, “treatments” such as acupuncture or homeopathy are increasingly promoted as strategies that”harness the power of placebo” without all the pesky costs or side effects of real medical interventions. But this is simply special pleading from purveyors and promoters. Unable to wish away the well-conducted trials that show them to be indistinguishable from placebos, they instead are spinning placebo effects as meaningful and worthy of pursuit – ideally with your favourite CAM therapy. Again, I’ll refer you to posts by David Gorski and Steven Novella who offer a more detailed description of how negative results can be spun to look positive. Because CAM’s effects are indistinguishable from placebo, we should not invest time and resources into pursuing them – we should instead focus on finding treatments that are demonstrably superior to placebo.

But what if physicians are already using placebos widely in practice? Setting aside the ethical issues for now, widespread placebo usage might suggest that physicians believe that placebos are effective treatments. And that’s the impression you may have had if you skimmed the medical headlines last week:

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Posted in: Clinical Trials, Epidemiology, Science and Medicine

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Worms, Germs, and Dirt: What Can They Teach Us About Allergies and Autoimmune Diseases?

Whipworms in the intestine

Whipworms in the intestine. Click to enlarge.

Humans evolved in an environment where they were exposed to animals, dirt, and a variety of pathogens and parasites. Our immune systems evolved to cope with that environment. Now most of us live in a different environment, with safe drinking water, flush toilets, food inspection, immunizations, and public sanitation. This means that we are far less likely than our ancestors to die of infectious diseases or to harbor intestinal worms. But it seems that the cleaner we get, the more likely we are to suffer from allergies and autoimmune diseases. One hypothesis is that our immune systems evolved to require early challenges by parasites and pathogens in order to develop properly. A hygienic environment fails to give our immune system the exercise it needs, resulting in imbalances and malfunctions.

The hygiene hypothesis was first proposed to explain observations like these:

  • Hay fever and allergies were less common in large families where children were presumably exposed to more infections through their siblings.
  • Polio attack rates were higher in high socioeconomic groups than in lower ones.
  • Allergies and many other diseases were less common in the developing world.

Investigation of these and other phenomena is contributing to a better understanding of the immune system, which is a good thing. At the same time, it has led some people to deliberately infect themselves with intestinal worms in an attempt to cure their allergies and autoimmune diseases, which may not be such a good thing. These treatments are far from ready for prime time, are risky, and they have a high yuck factor. The very idea of deliberately infecting yourself with worms is unpalatable, and finding wiggly live creatures in your stool or passing a 20 foot tapeworm are not generally considered to be pleasant experiences.  (more…)

Posted in: Book & movie reviews, Epidemiology, Evolution

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One Flu Into the Cuckoo’s Nest*

“I don’t seem able to get it straight in my mind….”
― Ken Kesey, One Flew Over the Cuckoo’s Nest

Influenza is going gangbusters at the moment. I like going to Google Flu trends as well as the CDC flu site to see what flu is doing. Using Google searches as a surrogate for infections is an interesting technique that public health officials have tried with less success in other illnesses but is not without utility. Behaviors of populations can presage a problem, my favorite example is the first hint of the 1993 massive Cryptosporidia diarrhea outbreak in Milwaukee was a sudden shortage of Kaopectate and Peptobismol. It appears there are more patients with flu like symptoms this year than  at the height of the H1N1 epidemic of 2009. We have lots of flu like illness, and per the CDC there are buckets of confirmed influenzaflu, but so far the season, while probably having more cases than 2009, the outbreak is clinically not the same.

Compare and contrast, the two words that defined undergraduate liberal arts essay assignments. Get out your blue books and compare and contrast influenza outbreaks from 2009 and 2013. You have one hour. (more…)

Posted in: Clinical Trials, Epidemiology, Public Health, Science and Medicine, Science and the Media, Vaccines

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The Sweetener Wars – HFCS Strikes Back

The health conscious and trendy public are a bit obsessed with the food they consume. This can be a good thing, to the extent that it results in a more healthful diet, but unfortunately those interested in improving their diet must wade through a great deal of misinformation before getting to accurate and helpful information.

For example, I recently gave a lecture (ironically on health information) at Google (you can view the entire talk here). Google is a progressive company that tries to help their employees stay healthy. They provide many snack stations and helpfully divide snacks into red, yellow, and green shelves. Employees can freely choose whatever snacks they want, but they are gently encouraged to choose from the more healthful green shelf and avoid the unhealthy red shelf. I noticed that beverages sweetened with sugar cane were placed on the green shelf, while those sweetened with artificial sweeteners like aspartame or Splenda were slumming on the red shelf. It was ironic to see such a high-tech company falling for the naturalistic fallacy.

Sugar cane sweetened sodas are becoming fashionable, mainly to avoid high fructose corn syrup (HFCS), which many claim is associated with obesity and increased cardiovascular risk. Jim Laidler did an excellent job reviewing this controversy two years ago on SBM. To me this represents a general tendency to try to understand a complex question by oversimplifying, specifically by avoiding perceived “villains.” It may seem overwhelming to grapple with all the complex information involved in basic dietary health choices, like which beverages are best. Following simple rules, such as avoiding single ingredients that are perceived to be “bad,” therefore has an appeal. I also think this is part of the appeal of the naturalistic fallacy, a simple litmus test to what is good vs bad.

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Posted in: Epidemiology, Nutrition

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Science, Evidence and Guidelines

Disclaimer:  I am a paid Medscape  blogger and writer, and since they are in part supported by advertisements from the Pharmaceutical companies,  indirectly I am in the thrall of Big Pharma.

I found Harriet’s post on the Medscape Connect topic of How do you feel about Evidence-Based Medicine? interesting.

I wondered about the breakdown of the comments by both specialty and opinions about SBM.  So I read the 226  comments and classified them by field and response.  I classified each response as disapprove, approve or nuanced.  It is not, obviously, a legitimate survey and there was more than a little subjective interpretation in deciding how to classify the responses.  I have no doubt that others would get different results; it is not methodologically sound analysis. The discussion was in the Family Medicine & Primary Care section, so it is unlikely to be representative of any population, including that of Family Practitioners and Primary Care Physicians.  I would bet, as in alternative medicine and most topics, Shruggies predominate and are the silent majority.

Even though I belong to what  a commentator referred to as the not so silent “militant wing” of SBM, I was surprised at my results: (more…)

Posted in: Epidemiology, Medical Academia, Pharmaceuticals, Science and Medicine

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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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