Understand what 鈥渉ealth risks鈥 mean鈥攁re they 鈥渞elative鈥 risks or 鈥渁bsolute鈥 risks. Claims can be misleading (and downright scary).
You鈥檝e seen the headlines: 鈥淏reakthrough therapy cuts risk of [name a disease] 60 percent!鈥, or 鈥淸Name your condition] patients have an 85 percent higher risk of [name a condition] than people who don鈥檛.鈥
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鈥攁s 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 鈥攗sing 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 鈥渞isk鈥:
- 鈥淩elative risk鈥 describes a ratio that compares the risk of getting sick (or the chances of getting better) between people who receive a 鈥渢reatment鈥 and a control group of people who don鈥檛.
- 鈥淎bsolute risk鈥 involves simple subtraction: It subtracts the risk to a 鈥渢reated鈥 population from that of an untreated or conventionally treated population.
Let鈥檚 say researchers divide 100 people equally into two groups, 50 who receive the treatment and 50 who don鈥檛. 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鈥檛. 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.
