Defining Health Risk: Confusing and Even Misleading

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Health Risk

Understand what “health risks” mean—are they “relative” risks or “absolute” risks. Claims can be misleading (and downright scary).

You’ve seen the headlines: “Breakthrough therapy cuts risk of [name a disease] 60 percent!”, or “[Name your condition] patients have an 85 percent higher risk of [name a condition] than people who don’t.”

The first case celebrates what appears to be a breakthrough, the second a cause for intense fear.

Research shows that most of us exaggerate not only the risks of many common or fearsome medical conditions, but also the benefits of new medical treatments.

Why do we exaggerate our own health risks—as well as our expectation of how medicine and medical care can benefit us? 

This is often due to the way the health information is communicated to —using relative change. Media reporting often aids and abets these exaggerations, especially in headlines.  

Risky Business

To discover why, consider the two main ways of defining “risk”:

  • “Relative risk” describes a ratio that compares the risk of getting sick (or the chances of getting better) between people who receive a “treatment” and a control group of people who don’t.
  • “Absolute risk” involves simple subtraction: It subtracts the risk to a “treated” population from that of an untreated or conventionally treated population.

Let’s say researchers divide 100 people equally into two groups, 50 who receive the treatment and 50 who don’t. Only three people who get the treatment get sick, but five people in the control group get sick. Expressed as a ratio 3/5, we learn that 60 percent who took the treatment improved compared to those who didn’t. A medical miracle!

Until you step back and look at the starting point (100 people). If within an untreated or conventionally treated population, five people typically get the condition (five percent), and with treatment, that number falls to three (three percent) the absolute risk is only two percent. Not nearly so miraculous.

Both statements of risk are accurate, but absolute risk offers context that gives a more complete picture of benefit and/or risk.

Health news and information sources can mislead readers or viewers in many other ways, but when reading about a new medical therapy or a dreaded condition on the rise, question the numbers carefully before engaging your emotions.

~ By  Margaret Boyles

About This Blog

Margaret Boyles lives in a wood-heated house in central New Hampshire. She grows vegetables, keeps chickens, swims in a backyard pond in summer, snowshoes in the surrounding woods in winter, and commutes by bike whenever possible.

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