epidemiology

Let's pretend that researchers are investigating acts of violence between players during hockey games. And let's further pretend that they are interested in determining if violent behavior has a racial component.

Would you be surprised to find out that most acts of violence happen between white players? Well, of course not. The National Hockey League (NHL) consists almost exclusively of white people. (A figure from 2011 claims the league is 93% white.) So, if the researchers do not control for the fact that most hockey players are white, they could come to the erroneous conclusion that white hockey players are more likely to be violent.

For this reason,...

The Spanish Flu of 1918, which caused a pandemic, is estimated to have killed about 2% of the world population, a death toll greater than the military deaths of World War I and World War II combined. Though they obviously would have lacked the technology and healthcare to do much about it, was there any way that public health officials could have foreseen that global plague?

Yes, possibly, suggests a new paper in the journal Annals of Epidemiology. A mostly mild wave of influenza cases early in 1918 could have served as a herald of the doom to come later that year.

In the northern hemisphere,...

The incidence of prostate cancer tripled between 1975 and the early 90’s. What changed? Sun exposure is an acknowledged risk factor in the development of melanoma – but oddly enough, for those with melanoma, a history of greater sun exposure is associated with a 50% better survival. How can sunlight be both good and bad? And women with higher socioeconomic status have twice the number of breast cancers diagnosed than their low socioeconomic status sisters. Does that mean that greater income somehow predisposes to breast cancer? How can all of these findings be true? Heisenberg.

Werner Heisenberg and his ‘Uncertainty Principle’ are at play and are the subject of a thought piece on the uncertainty principle’s consequences for medical studies. The Heisenberg Uncertainty Principle...

It turns out you can explain the spread of rioting as well as fake news by understanding the spread of a communicable disease, such as the flu. Both actions and ideas spread like a virus; you need both an infectious idea and a receptive audience. A recent article in Scientific Reports applies that metaphorical thinking and some mathematical formulations to the 2005 riots in France.

The metaphor comes from an epidemiologic model called SIR, for "susceptible, infected and recovered." It describes the interaction of the infected with the susceptible. For this article, let's ignore the recovered because rioters infrequently return for more rioting and we rarely change our opinions back to what we once believed.

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It is oft-repeated that correlation does not imply causation. But it does. That's precisely why epidemiologists and economists are so fascinated by correlations. Thus, it is far more accurate to say that correlation does not prove causation.

There are two major reasons for this. The first is because of confounders, hidden factors that are the true causes of the observed effect. For instance, one might be tempted to conclude that moving to Florida makes people develop Alzheimer's. But this correlation has been confounded by age; in reality, old people both retire to Florida and develop Alzheimer's. The Sunshine State is blameless....

Isn't it odd that Florida has so many people living with Alzheimer's Disease? If Erin Brockovich was investigating the case, she probably would conclude that it's something in the water.

The rest of us, however, know that there's nothing especially dangerous about Florida.* Old people all across America move to Florida for retirement, and Alzheimer's is a disease associated with aging. Ergo, Florida is not causing Alzheimer's; aging is.

Using the vernacular of epidemiology, aging in this example is known as a confounding variable. The apparent association between living in Florida and having Alzheimer's is confounded by age. If a researcher did not take age into consideration, he would draw incorrect conclusions about a link between geography and Alzheimer's....

Smoking really is as bad as everybody says it is.

A person's chance of getting lung cancer depends on how many years one has smoked, as well as how many cigarettes one has smoked per day. In general, according to the International Journal of Cancer, smoking makes a man nearly 24 times more likely to get lung cancer and a woman almost 8 times more likely. Put another way, smoking increases a man's risk of lung cancer by 2,300% and a woman's by 700%.

Lung cancer isn't the only thing a smoker needs to worry about. Smoking is linked to several different cancers, and it damages the cardiovascular, respiratory, and immune systems. Indeed, as the...

Microbiologist Stanley Falkow is credited with saying, "The goal of every bacterium is to become bacteria." Similarly, the goal of every pathogen is to infect a new host.

Pathogenic microbes face an evolutionary trade-off: On the one hand, they want to be as nasty as possible, because the nastier they are, often the easier it is to spread from one host to the next. Think of Vibrio cholerae, the causative agent of cholera, which upon infection can result in a person producing gallons of diarrhea. Death is due to dehydration, but not before the patient served as an incubator and excreted billions of more bacteria into the environment.

On the other hand, a microbe does not want to be too nasty. If it incapacitates or kills its host quickly, it will be difficult for...

When Erin Brockovich, an environmental activist, shook down Pacific Gas & Electric for $333 million for allegedly poisoning a community with hexavalent chromium and causing cancer and all sorts of other health problems, Julia Roberts portrayed the protagonist in a sensationalized blockbuster movie. It is unlikely, however, that Hollywood will be filming a sequel.

Why? Because not only was Ms. Brockovich wrong, but the State of California has now partially repudiated what she fought for.

Erin Brockovich, Junk Scientist

We've known for a long time that Ms. Brockovich used junk science to score a jackpot settlement. She used a common rhetorical trick, known as the Texas...

A new study in the Journal of the American Medical Association found that 99% of donated brains from people who played in the NFL showed signs of chronic traumatic encephalopathy (CTE), a type of neurodegenerative disease that is thought to result from persistent brain injury from knocks to the head. Signs of CTE were also noted in the brains of 91% of people who played the sport in college and 21% who played in high school.

Predictably, headline writers went crazy:

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