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Archive for Epidemiology

Confusing overdiagnosis for an “epidemic” of thyroid cancer in Japan after Fukushima

A Japanese girl being screen for thyroid cancer.

A Japanese girl being screen for thyroid cancer.

One of my favorite topics to blog about for SBM is the topic of overdiagnosis and overtreatment. These are two interrelated phenomena that most people are blissfully unaware of. Unfortunately, I’d also say that the majority of physicians are only marginally more aware than the public about these confounders of screening programs, if even that.

Overdiagnosis has long been appreciated to be a major impediment to translating programs to screen for disease into better outcomes in a number of diseases but has only recently really seeped into the public consciousness, beginning in particular in 2009 when the United States Preventative Services Task Force (USPSTF) issued mammography recommendations that pushed back the recommended age to start screening to 50. Certainly, the concept of overdiagnosis is counterintuitive. After all, why do we screen for disease in asymptomatic people? The reason is simple—and maddeningly intuitive. We screen for disease based on the belief that catching potentially deadly diseases like cancer early, before they produce clinical symptoms, will allow earlier intervention and save lives. It seems blindingly obvious that this should be the case, doesn’t it? Unfortunately, real life biology and pathophysiology aren’t quite so neat and tidy, and the relationship between early detection and improved survival is muddied by phenomena such as lead time bias and the Will Rogers effect, in addition to overdiagnosis.

What is overdiagnosis? In brief, it is the detection of pathology or disease that, if left untreated, would never endanger the life of a patient or even harm him. Note that overdiagnosis is not the same thing as a false positive. A false positive occurs when a test detects disease that isn’t really there; in contrast with overdiagnosis there is definite pathology. The disease being screened for is there, at least in an early form. It’s just that, at the very early stage detected, it’s either not progressive or so indolent that the patient will grow old and die of something else before it would ever cause a problem. Indeed, it’s been estimated that as many as one in three breast cancers detected by mammography in asymptomatic women might be overdiagnosed and that one in five might spontaneously regress. However, because we don’t know which ones are unlikely to cause harm and haven’t worked out a safe method of observing them and intervening if they look as though they are progressing, we are obligated to treat them all when discovered. The problem of overdiagnosis has led to multiple alterations in what once were considered definitive recommendations for screening mammography, first by the USPSTF and most recently by the American Cancer Society.
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Posted in: Cancer, Epidemiology

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Are the recommended childhood vaccine schedules evidence-based?

The vaccine schedule: Safe and efficacious.

The vaccine schedule: Safe and efficacious.

We write about vaccines a lot here at SBM, and for a very good reason. Of all the medical interventions devised by the brains of humans, arguably vaccines have saved more lives and prevented more disability than any other medical treatment. When it comes to infectious disease, vaccination is the ultimate in preventive medicine, at least for diseases for which vaccines can be developed. We also know that when vaccination rates fall, it opens the door for diseases once controlled to come roaring back. We saw this phenomenon with the measles a year ago in the Disneyland measles outbreak. We’ve seen it around the country, with measles outbreaks occurring in areas where a lot of antivaccine and vaccine-averse parents live. Perhaps the most spectacular example occurred in the UK, where prior to Andrew Wakefield’s fraudulent case series in The Lancet that was used to link the MMR vaccine to autism, measles was under control; it came roaring back as MMR uptake plummeted in the wake of the publicity his research engendered. By 2008, ten years after Wakefield’s case series was published, measles was again endemic in the UK. Measles outbreaks flourished. Although MMR uptake is improving again in the UK, there remains a reservoir of unvaccinated children aged 10-16 who can transmit the virus.

Thanks, Andy.

Fortunately, Wakefield has been relegated to sharing the stage with crop circle chasers, New World Order conspiracy theorists, sovereign citizen cranks, and other antivaccine cranks like Sherry Tenpenny. Unfortunately, the damage that he has done lives on and has metastasized all over the developed world. Given the persistence of the antivaccine movement, which fuels concerns about vaccines in parents who are not themselves antivaccine but are predisposed to the antivaccine message because they distrust government and/or big pharma or have a world view that overvalues “naturalness,” I was quite interested in an article that appeared in The BMJ last week. Basically, it asked the question “Is the timing of recommended childhood vaccines evidence based?
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Posted in: Clinical Trials, Epidemiology, Public Health, Vaccines

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Air Pollution and Public Health

airpollution

Public health measures are those not aimed at individuals but at society as a whole, or subgroups within society. Physicians are charged not only with promoting the health of their own patients, but as a profession we (and health care professions in general) are charged with promoting the public health.

Public health measures, however, are highly likely to cross into politically charged areas. This should not deter the promotion of public health.

Issues that we deal with regularly involving public health include vaccination programs and laws surrounding vaccine requirements, fluoridation of public water supplies, helmet laws, and even gun laws. We have never, however, written about air pollution as a public health concern (except for dubious claims that air pollution is linked to autism).

The health risk of air pollution

Air pollution as a health risk is nothing new, but several recent studies are focusing attention on this issue. Recently the Royal College of Physicians produced a report in which they claim that 40,000 deaths per year in the UK can be attributed to poor air quality, both indoors and outdoors. (more…)

Posted in: Epidemiology, Public Health

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Zika virus, microcephaly, and calls to bring back DDT

zika-virus-mosquito

If there’s one thing I’ve learned over the last decade-plus of blogging about medicine and alternative medicine, it’s that any time there is an outbreak or pandemic of infectious disease, there will inevitably follow major conspiracy theories about it. I saw it during the H1N1 pandemic in the 2009-2010 influenza season, the Ebola outbreak in late 2014, and the Disneyland measles outbreak last year, when cranks of many stripes claimed that either the outbreaks themselves were due to conspiracies (usually, but not limited to, conspiracies to promote the “depopulation” vaccination agenda of—who else?—Bill Gates) or that nefarious forces were seizing on the outbreak to take away our freedom. The second thing I’ve learned is that inevitably people will try to impose their ideology on to the disease and try to use outbreaks to push their own ideological agenda. Indeed, the Ebola outbreak, for example, was rapidly seized on by politicians to promote quarantines and to halt immigration from the affected countries. This year, the biggest infectious disease-related story thus far is the Zika virus outbreak in Brazil that has been linked to microcephaly and other birth defects, and it’s a case of the same stuff, different year.

The Zika virus is a mosquito-borne flavivirus related to dengue virus and transmitted primarily by Aedes aegypti mosquitoes. On the surface, this virus would appear to be relatively benign, with 80% of those infected by it remaining asymptomatic, while the other 20% suffer from what is usually a self-limited, relatively mild illness characterized by fever, rash, arthralgias (joint aches), and conjunctivitis. In the grand scheme of things, after decades of being endemic in many tropical areas Zika virus infection probably didn’t seem so bad and didn’t appear to be much of a public health priority in the regions where Aedes aegypti mosquitoes live, mainly tropical regions in South and Central America, Africa, southeast Asia, and the Pacific islands. Then came the evidence that prenatal infection might cause microcephaly, and everything changed. Not surprisingly, conspiracy theories galore arose with social media speed, as did the ideologically motivated overselling of proposed solutions, such as bringing back DDT to combat the mosquito carrying the disease.
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Posted in: Basic Science, Epidemiology, History, Politics and Regulation

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Holding the supplement industry to account: Can we learn from tobacco regulation?

When it comes to supplements, you can't trust what's on the label

When it comes to supplements, you can’t trust what’s on the label

The idea that “natural” products are safe and effective has been so effectively marketed to us that many don’t recognize it as a fallacy. Much of the supplement industry is built around an appeal to nature. Supplements are described as natural, gentle, and “holistic”. Medicine, especially prescription drugs, is the opposite. They’re “chemicals”. They’re risky and dangerous – just look at that list of side effects! Supplements are packaged beautifully, have impressive claims, and are for sale at Whole Foods. Drugs are hazardous: They may come in a plain vial, with warning labels, detailed information sheets, and cautious statements about their effectiveness. Is it any wonder that many consumers, when faced with health concerns or medical issues, instinctively think of supplements as a safer alternative? Purveyors of supplements and alternative medicine have leveraged this fallacy so effectively that it’s even guided the regulations that allow their sale. Regrettably, the result is a marketplace that puts consumers’ interests last. The supplement industry has completely stacked the odds against the consumer, challenging their ability to make informed decisions about their health. Most supplements on the market have never been properly tested for safety or effectiveness. And those that have been tested have largely been shown to be ineffective – or in the case of products like vitamins, often unnecessary. And while there are undoubtedly some ethical companies out there, the industry is regularly revealed to resemble a wretched hive of scum and villainy. Despite this, the industry has gone from success to success – in terms of sales, at least. In 1994 supplement sales were about $4 billion in the US. It’s now a $37 billion industry that is remains only lightly regulated – or largely unregulated. With recent action taken against fraudulent products, there are more questions than ever about how to force the supplement industry to make consumer protection a priority. A new paper in Drug Testing and Analysis makes a provocative suggestion: Local and state governments already regulate another hazardous product: tobacco. Can lessons learned from the tobacco wars improve the safety of supplements? (more…)

Posted in: Epidemiology, Health Fraud, Herbs & Supplements, Politics and Regulation, Public Health

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No, Purell Does Not Breed Super-Anything

Pictured:  Mechanism of pumpy doom, or savior to us all?  Neither!

Pictured: Superbug spawner, or savior to us all? Neither!

Recently, I was sitting in a meeting and reached for the dispenser of Purell hand sanitizer sitting on the conference room table. A colleague of mine gave a small, rueful shake of her head to the person on her other side. Apparently I had erred. I asked what was the matter, and got a brief answer to the effect of “because superbugs.” We exchanged nothing more about it; the interaction was over before the alcohol had dried from my hands.

I wouldn’t have thought anything of such an interaction with anyone else, but my colleague is a PhD student in immunology, six years older and more schooled than I, doing her doctoral research in a lab run by a physician-scientist — a specialist in infectious disease, no less. A touch ironic.

And so I noticed a need for some mythbusting: alcohol-based hand sanitizers do not breed resistant bacteria. (more…)

Posted in: Epidemiology, Evolution, Public Health, Science and Medicine

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Do Helmets Prevent Head Injuries?

320px-Humpty_was_pushed_(298669543)
A cycling enthusiast asked me about helmets. It seems compellingly obvious to me that a head impacting the pavement without a helmet is likely to sustain more damage than a head protected by a helmet. He challenged that, citing a BMJ article by Ben Goldacre that questioned whether the evidence showed that helmets do any good. He said I was making a non-evidence-based assumption and challenged me to actually look at the evidence, so I did.

Goldacre says there is a:

complex contradictory mess of evidence on the impact of bicycle helmets. Like most places where there’s controversy and disagreement, this is a great opportunity to walk through the benefits and shortcomings of different epidemiological techniques, from case control studies to modeling.

He proceeds to give a lesson in epidemiology. He points out that there are a lot of emotion involved, and that epidemiologic studies, because of their inherent imperfections, are probably not capable of resolving the debate.

There are basically two questions:

  1. What is the effect of wearing a helmet for the individual?
  2. What is the effect of a public policy that promotes or requires helmet use?

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Posted in: Epidemiology, Politics and Regulation

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Screening for disease in people without symptoms: The reality

One of the most contentious questions that come up in science-based medicine that we discuss on this blog is the issue of screening asymptomatic individuals for disease. The most common conditions screened for that we, at least, have discussed on this blog are cancers (e.g., mammography for breast cancer, prostate-specific antigen screening for prostate cancer, ultrasound screening for thyroid cancer), but screening goes beyond just cancer. In cancer, screening is a particularly-contentious issue. For example, by simply questioning whether mammography saves as many lives lost to breast cancer as advocates claim, one can find oneself coming under fire from some very powerful advocates of screening who view any questioning of mammography as an attempt to deny “life-saving” screening to women. That’s why I was very interested when I saw a blog post on The Gupta Guide that pointed me to a new systematic review by John Ioannidis and colleagues examining the value of screening as a general phenomenon, entitled “Does screening for disease save lives in asymptomatic adults? Systematic review of meta-analyses and randomized trials.”

Before I get into the study, let’s first review some of the key concepts behind screening asymptomatic individuals for disease. (If you’re familiar with these concepts, you can skip to the next section.) The act of screening for disease is based on a concept that makes intuitive sense to most people, including physicians, but might not be correct for many diseases. That concept is that early intervention is more likely to successfully prevent complications and death than later intervention. This concept is particularly strong in cancer, for obvious reasons. Compare, for example, a stage I breast cancer (less than 2 cm in diameter, no involvement of the lymph nodes under the arm, known as axillary lymph nodes) with a stage III cancer (e.g., a tumor measuring greater than 5 cm and/or having lots of axillary lymph nodes involved). Five year survival is much higher for treated stage I than for treated stage III, and, depending on the molecular characteristics, the stage I cancer might not even require chemotherapy and can be treated with breast conserving surgery (“lumpectomy” or partial mastectomy) far more frequently than the stage III cancer. So it seems intuitively true that it would be better to catch a breast cancer when it’s stage I rather than when it’s stage III.
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Posted in: Cancer, Clinical Trials, Epidemiology, Public Health

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Hot-Zone Schools and Children at Risk: Shedding light on outbreak-prone schools

The subject of parental vaccine refusal and the impact that has on disease outbreaks has been covered many times on SBM and elsewhere. I apologize to our readers who are growing tired of the subject, but there is perhaps no subject more deserving of focus and repetition. There’s also an important angle to the discussion that I’ve written on previously and which deserves more attention, and that is the importance of the pro-vaccine parent voice, and the need for that voice to be heard.

It never ceases to amaze me how few of the parents I know think about the risk to their own children from vaccine-exempt children in their schools and communities. Even parents who do think about this rarely seem concerned enough to speak up or even discuss it with others, let alone become active in doing something about it. With the rise in vaccine-preventable disease outbreaks, including the current high-profile Disneyland measles outbreak, and the ongoing pertussis epidemic in California, the tide seems at least to be turning slightly. The dramatic impact that vaccine refusal and the resultant decline in herd-immunity can have on a community is now penetrating the public consciousness. My hope is that parental awareness and outrage grow regarding the flagrant disregard of science, common sense, and citizenship exhibited by those parents who refuse to properly vaccinate their children. My hope is that the culture of tolerance of this intolerable anti-science threat begins to turn, and that it is no longer seen as acceptable for some parents to put the safety of others at risk.

Which brings me to the focus of this post. (more…)

Posted in: Epidemiology, Legal, Public Health, Science and Medicine, Vaccines

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Is cancer due mostly to “bad luck”?

One of the more difficult conversations to have with a patient as a cancer doctor occurs when a patient, recently informed of her diagnosis of, for example, breast cancer, asks me, “Why did I get this? What caused it?” What almost inevitably follows is an uncomfortable conversation in which explanations of the multiple known causes of breast cancer do not satisfy the patient. The reason, of course, is because when a patient asks, “What caused it?” she doesn’t mean what causes breast cancer in general or in statistical terms. Rather, she means, what caused my breast cancer? It’s a question that can only occasionally be answered. For instance, if it’s lung cancer and the patient is a smoker, then it was almost certainly smoking that caused the cancer, because lung cancer is a relatively rare cancer in the absence of smoking. In the case of breast cancer, contrary to the prevailing belief that leads women with breast cancer to be puzzled about how they could get it when there’s “no cancer” in their families, only around 5-10% of cases have a familial or genetic component. That means that around 90% of breast cancers are what we call “sporadic,” which means that we can’t identify a specific cause. Or, as I like to say, “We just don’t know.” Worse, in the case of breast cancer, the environmental factors we know about appear to contribute modestly at best to the risk of cancer. (More on this later.)

Understandably, patients hate hearing “We just don’t know,” some vague handwaving about genes, and that there is nothing that we know of that they did that caused their cancer. People—including oncologists—really don’t like the concept of “sporadic” cancer, mainly because humans crave explanation. The default assumption is that everything must happen for a reason and there must be a cause for every disease or cancer. Perhaps the most ridiculously emphatic statement of this that I’ve encountered thus far comes from (who else?) über-quack Mike Adams when he heaped contempt on the idea of sporadic disease as “spontaneous disease.” He did this in the context of a story describing how, after Dr. Mehmet Oz had followed recommended care and undergone screening colonoscopy to look for polyps, he was shocked that he actually had some. This led Adams, in his usual inimitable fashion, to construct a straw man so massive that it could be seen from space when he set it on fire, declaring that “colon polyps, in other words, appear without any cause!” and that “mainstream medicine…believes in the theory of ‘spontaneous disease’ that ‘strikes’ people at random.”

Not exactly.

On the other hand, there is a lot of randomness in disease, not just cancer, as hard as it is for Mike Adams, or anyone to accept. Just because there is a varying amount of randomness in who gets a disease does not mean that mainstream medicine claims there is no cause to these diseases. Rather, for diseases like cancer, it’s a stochastic process, meaning that chance can play a role—sometimes a big role—in determining who gets sick. Indeed, just last week there was more evidence supporting this idea published in Science. Unfortunately, much of the mainstream press coverage presented the message of the paper a bit too simplistically. Even more unfortunately, it was the authors who encouraged this, as did the Johns Hopkins University press release about the study, which was entitled “Bad Luck of Random Mutations Plays Predominant Role in Cancer, Study Shows“. Yes, I groaned when I read this title.
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Posted in: Basic Science, Cancer, Epidemiology, Science and the Media

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