Alcohol and cancer: What does a ‘500% increase’ in risk really mean?

NBC Nightly News ran a story about the cancer risks related to alcohol consumption.

But instead of communicating those risks in a way that would educate and inform, NBC’s coverage was an example of misinformation and fear-mongering.

Consider this graphic touting what the reporter describes as a “staggering increased risk of 500%” for head and neck cancers from heavy drinking.

What’s truly staggering here is NBC’s failure to provide any context around these statistics. 500% is a big, scary number. But what does it really mean and how worried should viewers be? Without knowing how common these cancers are to begin with, it’s impossible to say. A 500% increase to a tiny number might still leave us with a very small risk.

That’s why we always urge journalists to report risks in absolute terms. We’ve even published an informative primer on the topic to help.

The same problem is evident with all of the other figures presented in the story. What does a 17% increase in colon cancer risk look like for women who drink a glass of wine a day?

And breast cancer? The story claims a 4% increase for women who are “light” drinkers. But “light” drinking is never even defined. Presumably this means less than one serving of alcohol per day (a level which the NBC report defines as “moderate” drinking).

So is that 4% increase enough to justify abstaining from even the odd glass of Cabernet? There’s nothing here that will help women make sense of the risks or balance them against the pleasure they might derive from an occasional cocktail.

Read on to see what the actual percentages could mean.

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