Why does the media muck up health coverage?

Journalists consistently incite panic over small -- but novel and frightening-sounding -- health risks like SARS and bioterrorism, and all but ignore major ones like lack of exercise and smoking, according to new research. “The intensity of media coverage inversely correlated with the actual number of deaths,” report researchers Larisa J Bomlitz and Mayer Brezis in a new study on the deleterious effect on public health of the American mass media, published in the Journal of Public Health online last Friday.

Just check out the study’s findings in the diagram to the right -- the greater the risk, the less reporters seem to care.

What’s behind this pattern? The best way to explain it is not the desire to sell more newspapers, as you might expect. Rather, the answer lies in an economics analysis of cognitive bias called “prospect theory.”

Bomlitz and Brezis offer a convincing explanation in their discussion of their results (the data they used is from 2003, hence the number of SARS stories):

“[The inversely correlated health reporting trend is] consistent with psychological theory on cognitive biases, whereby a small change is perceived as more notable than a stable information signal, even if the latter may convey a more significant message – as described by the prospect theory. Perceptual systems are designed to enhance the accessibility of changes and differences: cold water feels colder if our other hand is immersed in warm water because perception is deter mined by comparison. The magnitude of a stimulus and its perceived significance derive from the contrast between that stimulus and other prior and simultaneous stimuli. The prospect theory extends the principle underlying these perceptual illusions to the explanation of cognitive biases in financial or health-related decisions.”

The study cites as its source Daniel Kahneman, a Princeton psychologist, who described prospect theory in his 2002 Nobel Prize lecture, which is online here (PDF).

In his lecture, Dr Kahneman explained that people react differently to health risks depending on whether they’re framed as survival rates or mortality rates. Dr Kahneman mentioned a few neat demonstrations of this cognitive bias. One is “The Asian Disease” problem:

Imagine that the United States is preparing for the outbreak of an unusual Asian disease, which is expected to kill 600 people. Two alternative programs to combat the disease have been proposed. Assume that the exact scientific estimates of the consequences of the programs are as follows:

If Program A is adopted, 200 people will be saved

If Program B is adopted, there is a one-third probability that 600 people will be saved and a two-thirds probability that no people will be saved
Which of the two programs would you favor?

In this version of the problem, a substantial majority of respondents favor program A, indicating risk aversion. Other respondents, selected at random, receive a question in which the same cover story is followed by a different description of the options:

If Program A’ is adopted, 400 people will die

If Program B’ is adopted, there is a one-third probability that nobody will die and a two-thirds probability that 600 people will die

A clear majority of respondents now favor program B’, the risk-seeking option. Although there is no substantive difference between the versions, they evidently evoke different associations and evaluations. This is easiest to see in the certain option, because outcomes that are certain are over-weighted relative to outcomes of high or intermediate probability (Kahneman & Tversky, 1979). Thus, the certainty of saving people is disproportionately attractive, and the certainty of deaths is disproportionately aversive.

So SARS and bioterrorism are frightening because of their rarity and their high mortality rates, even though the absolute number of deaths is very low; the opposite is true of lack of exercise and smoking.

And that’s the explanation for that seemingly inviolable law of journalism: “If it bleeds, it leads.”

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University of Minnesota journalism professor Gary Schwitzer is one of the most astute and intelligent critics of misleading, erroneous and fear-mongering health reporting. He’s the publisher of US health-news monitoring site HealthNewsReview.org and he’s associated with its Canadian sister site, Media Doctor Canada.

Professor Schwitzer also has a great blog. Just last week he wrote about an example of prospect theory and cognitive bias in The New York Times’s coverage of websites that offer information on breast cancer.

The New York Times uses a headline, "Most Breast Cancer Sites Get It Right" over a story that begins:

The Internet is filled with unreliable health information and bogus claims. But sites dedicated to breast cancer information appear to have a high level of accuracy, a new study shows.

Texas researchers recently analyzed 343 Web pages, retrieved using search engines that consumers are likely to use when seeking information about breast cancer. The study, published online today in the medical journal Cancer, turned up 41 inaccurate statements on 18 of the Web sites, or an error rate of just 5.2 percent.

But that "just 5.2 percent" is the focus of the headline and the lead in a Reuters wire service story on the same study, but headlined, "Some breast cancer websites inaccurate." The story begins:

Five percent of breast cancer Web sites have mistakes, with those involving alternative or complementary medicine the most likely to be misleading, U.S. researchers reported on Monday.

So is an error rate of "only" 5% good - and worthy of headlines? Or is an error rate of 5% "bad" and worthy of the headline?

Here’s a link to the study’s abstract, if you want to decide for yourself.


IMAGE: "Misrepresentation of health risks by mass media," Bomlitz and Brezis, Hebrew University, Journal of Public Health advanced access, February 15, 2008

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