Articles

Posts Tagged epidemiology

New evidence, same conclusion: Tamiflu only modestly useful for influenza

Tamiflu

Does Tamiflu have any meaningful effects on the prevention or treatment of influenza? Considering the drug’s been on the market for almost 15 years, and is widely used, you should expect this question has been answered after 15 flu seasons. Answering this question from a science-based perspective requires three steps: Consider prior probability, be systematic in the approach, and get all the data. It’s the third step that’s been (until now) impossible with Tamiflu: Some data was unpublished. In general, there’s good evidence to show that negative studies are less likely to be published than positive studies. Unless unpublished studies are included, systematic reviews are more likely to miss negative data, which means there’s the risk of bias in favor of an intervention.

The absence of a full data set on Tamiflu (oseltamivir) and the other neuraminidase inhibitor Relenza (zanamivir) became a rallying point for BMJ and the AllTrials campaign, which seeks to enhance the transparency and accessibility of clinical trials data by challenging trial investigators to make all evidence freely available. (Reforming and enhancing access to trial data was one of the most essential changes recommended by Ben Goldacre in his book, Bad Pharma.) In 2009, Tamiflu’s manufacturer, Hoffman-La Roche committed to making the Tamiflu data set available to investigators. Now after four years of back-and-forth between BMJ, investigators, and Roche, the full clinical trials data set has been made freely available. An updated systematic review was published today in BMJ (formerly The British Medical Journal), entitled “Oseltamivir for influenza in adults and children: systematic review of clinical study reports and summary of regulatory comments.” This will be a short post covering the highlights. As the entire study and accompanying data are freely available, I’ll await continued discussion in the comments. (more…)

Posted in: Clinical Trials, Pharmaceuticals, Public Health

Leave a Comment (30) →

Autism prevalence: Now estimated to be one in 68, and the antivaccine movement goes wild

There used to be a time when I dreaded Autism Awareness Month, which begins tomorrow. The reason was simple. Several years ago to perhaps as recently as three years ago, I could always count on a flurry of stories about autism towards the end of March and the beginning of April about autism. That in and of itself isn’t bad. Sometimes the stories were actually informative and useful. However, in variably there would be a flurry of truly aggravating stories in which the reporter, either through laziness, lack of ideas, or the desire to add some spice and controversy to his story, would cover the “vaccine angle.” Invariably, the reporter would either fall for the “false balance” fallacy, in which advocates of antivaccine pseudoscience like Barbara Loe Fisher, Jenny McCarthy, J. B. Handley, Dr. Jay Gordon, and others would be interviewed in the same story as though they expressed a viewpoint that was equally valid as that of real scientists like Paul Offit, representatives of the CDC, and the like. Even if the view that there is no good evidence that vaccines are associated with an increased risk of autism were forcefully expressed, the impression left behind would be that there was actually a scientific debate when there is not. Sometimes, antivaccine-sympathetic reporters would simply write antivaccine stories.

I could also count on the antivaccine movement to go out of its way to try to implicate vaccines as a cause of the “autism” epidemic, taking advantage of the increased media interest that exists every year around this time. Examples abound, such as five years ago when Generation Rescue issued its misinformation-laden “Fourteen Studies” website, to be followed by a propaganda tour by Jenny McCarthy and her then-boyfriend Jim Carrey visiting various media outlets to promote the antivaccine message.
(more…)

Posted in: Diagnostic tests & procedures, Epidemiology, Neuroscience/Mental Health, Science and the Media, Vaccines

Leave a Comment (128) →

Vaccines work. Period.

Over my blogging “career,” which now stretches back nearly nine years, and my hobby before that of engaging in online “debates” on Usenet newsgroups back before 2004, I developed an interest in the antivaccine movement. Antivaccinationism, “antivax,” or whatever you want to call it, represents a particularly insidious and dangerous form of quackery because it doesn’t just endanger the children whose parents don’t vaccinate them. It also endangers children who are vaccinated, because vaccines are not 100% effective. The best vaccines have effectiveness rates in the 90%-plus range, but that still leaves somewhere up to 10% of children unprotected. Worse, because herd immunity requires in general approximately 90% of the population and above to be vaccinated against a vaccine-preventable disease to put the damper on outbreaks, it doesn’t take much of a degradation of vaccination rates to put a population in danger of outbreaks. That’s why, even though overall vaccine uptake is high in the US, we still see outbreaks, because there are areas with pockets of nonvaccinators and antivaccinationists who drive vaccine uptake down to dangerous levels. We’ve seen this in California and elsewhere. Other countries have observed even more dramatic examples, the most well-known being the way that fear of the MMR vaccine stoked by Andrew Wakefield’s bad science and the fear mongering of the British press led MMR uptake to plummet. The result? Measles came roaring back in the UK and Europe, from having been considered under control in the 1990s to being endemic again by 2008.

As much as I get chastised by concern trolls for saying this, to antivaccinationists it really is all about the vaccines. Always. They blame autism, other neurodevelopmental conditions, and a wide variety of chronic diseases on vaccines, without evidence that there is even a correlation. They even falsely blame sudden infant death syndrome (SIDS) on vaccines, even though there is no evidence of an association and, indeed, existing evidence suggests that vaccines likely have a protective effect against SIDS more than anything else. No matter what happens, no matter what the evidence says, antivaccinationists will always find a way to blame bad things on vaccines, even going so far as to claim at times that shaken baby syndrome is a misdiagnosis for vaccine injury.

One thing, however, that is often forgotten, is that they also do their utmost to downplay the beneficial effects of vaccines. One such tactic is for antivaccinationists to claim that the pertussis vaccine doesn’t work because we are seeing resurgences of pertussis even in the face of high vaccine uptake. For example, another common trope is what I like to refer to as the “vaccines didn’t save us” or the “vaccines don’t work” gambit, in which it is pointed out that the introduction of vaccines doesn’t correlate tightly with drops in mortality from various diseases. Julian Whitaker even used this gambit when he debated Steve Novella. The fundamental flaw in this trope neglects the contribution of better medical care to the survival of more victims of disease, which decreased mortality. If you look at graphs of disease incidence you will see a profound and powerful effect of the introduction of vaccines on specific vaccine-preventable diseases. In other words, vaccines work. (more…)

Posted in: Epidemiology, Public Health, Vaccines

Leave a Comment (134) →

Everything we eat causes cancer…sort of

Read meat causes cancer. No, processed meat causes cancer. OK, it’s both read meat and processed meat. Wait, genetically modified grain causes cancer (well, not really). No, aspartame causes cancer. No, this food coloring or that one causes cancer.

Clearly, everything you eat causes cancer!

That means you can avoid cancer by avoiding processed meats, red meat, GMO-associated food (no, probably not), aspartame, food colorings, or anything “unnatural.” Or so it would seem from reading the popular literature and sometimes even the scientific literature. As I like to say to my medical students, life is a sexually transmitted fatal disease that gets us all eventually, but most of us would like to delay the inevitable as long as possible and remain as healthy as possible for as long as possible. One of the most obvious ways to do accomplish these twin aims is through diet. While the parameters of what constitutes a reasonably healthy diet have been known for decades, diet still ranks high on the risk of concerns regarding actions we take on a daily basis that can increase our risk of various diseases. Since cancer is disease (or, I should say, cancers are diseases) that many, if not most, people consider to be the scariest, naturally we worry about whether certain foods or food ingredients increase our risk of cancer.

Thus was born the field of nutritional epidemiology, a prolific field with thousands of publications annually. Seemingly, each and every one of these thousands of publications gets a news story associated with it, because the media love a good “food X causes cancer” or “food Y causes heart disease” story, particularly before the holidays. As a consequence, consumers are bombarded with what I like to call the latest health risk of the week, in which, in turn, various foods, food ingredients, or environmental “toxins” are blamed and exonerated for a panoply of health problems, ranging from the minor to the big three, cardiovascular disease, diabetes, and cancer. It’s no wonder that consumers are confused, reacting either with serial alarm at each new “revelatory” study or with a shrug of the shoulders as each new alarm joins other alarms to produce a tinnitus-like background drone. Unfortunately, this cacophony of alarm also provides lots of ammunition to quacks, cranks, and crackpots to tout their many and varied diets that, they promise, will cut your risk of diseases like cancer and heart disease to near zero—but only if adhered to with monk-like determination and self-denial. (Yes, I’m talking about you, Dean Ornish, among others.)

All of this is why I really wanted to write about an article I saw popping up in the queue of articles published online ahead of print about a month ago. Somehow, other topics intervened, as did my vacation and then the holidays, and somehow I missed it last week, even though a link to the study sits in my folder named “Blog fodder.” Fortunately, it just saw print this week in its final version, giving me an excuse to make up for my oversight. It’s a study by one of our heroes (despite his occasional misstep) here on the SBM blog, John Ioannidis. It comes in the form of a study by Jonathan D. Schoenfeld and John Ioannidis in the American Journal of Clinical Nutrition entitled, brilliantly, Is everything we eat associated with cancer? A systematic cookbook review.
(more…)

Posted in: Cancer, Nutrition

Leave a Comment (36) →

Hyping Health Risks

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.
(more…)

Posted in: Book & movie reviews, Science and the Media

Leave a Comment (27) →