How Not to Get Misled by Health Statistics

Description

There are few things that can make you feel dumber than a statistic. That's because there are few things that are more misleading. Suppose one cholesterol drug reduces your risk of dying from a heart attack by 42% and another reduces your risk by only 3.5%. No question about which one you'd take, right? Now suppose they're both the same drug.

That's just one of the many muddles described in the newly released book Know Your Chances: Understanding Health Statistics, by Drs. Steven Woloshin, Lisa Schwartz and H. Gilbert Welch. If you think you're a smart and skeptical reader of health news and pharmaceutical ads, you may want to read this book first and then think again. (See the top 10 medical breakthroughs of the past year.)

The cholesterol numbers are drawn from an advertisement for the statin Zocor - a drug that the authors are careful not to dismiss out of hand, since it can indeed save lives, just not as many as its makers would like you to believe. The ad openly touts the 42% figure, which is based on a study in which 111 out of 2,221 people with heart disease who used Zocor later died of a heart attack. In a control group of heart patients who used a placebo, 189 out of 2,223 died. So the fact is there were indeed 42% fewer deaths among the Zocor users, compared with the controls. But when you consider the absolute risk of death in either group, the results are somewhat less stunning. The risk of death in the placebo group was just 8.5%, compared to 5% in the Zocor group - a difference of a mere 3.5%. Both survival numbers are correct, but which one would you use if you were writing the ad copy?

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http://news.yahoo.com/s/time/20090325/hl_time/08599188733500

http://news.yahoo.com/s/time/20090325/hl_time/08599188733500