Thursday, April 1, 2010

Why statins should not be widely prescribed, or the difference between relative and absolute risk

In The New York Times yesterday, Duff Wilson did a great job of explaining why many medical experts question the growing use of cholesterol-lowering statins in people without heart problems. He reported on new studies showing the risks of otherwise healthy people taking statins, and he exposed the huge conflict of interest by the scientist who led the study that enabled AstraZeneca to win FDA approval for marketing its statin, Crestor, to people without heart problems. (The scientist, Dr. Paul Ridker, a cardiologist at Harvard and Brigham and Women's Hospital, receives lucrative royalties on the test used in the study to determine whether people without visible heart problems might benefit from Crestor, There is much dispute over whether test itself, which measures an elevated level of inflammation in the body, indicates underlying heart problems).

Wilson also performed another estimable service: he highlighted the difference between relative risk and absolute risk. Relative risk is the statistical difference in outcome between a control group and a group taking an active drug in a study, whereas absolute risk is the actual number of people who might actually benefit from the drug. Most randomized clinical trials only report relative risk, which often inflates the benefits of the drug being studied.

So, as Wilson explained:

The rate of heart attacks, for example, was 0.37 percent, or 68 patients out of 8,901 who took a sugar pill. Among the Crestor patients it was 0.17 percent, or 31 patients. That 55 percent relative difference between the two groups translates to only 0.2 percentage points in absolute terms — or 2 people out of 1,000.

And then he goes on to put the difference into even clearer context:

Stated another way, 500 people would need to be treated with Crestor for a year to avoid one usually survivable heart attack. "That’s statistically significant but not clinically significant,” said Dr. Steven W. Seiden, a cardiologist in Rockville Centre, N.Y., who is one of many practicing cardiologists closely following the issue.

Well done, Duff!

On another note, I just wanted to let readers know that I am taking a hiatus from weekly blogging. I may still wade in now and then to blog about a timely issue (when I can't resist), but it's time to turn my attention to another project.