High Cholesterol and the Unmentioned Statistic

According to Darshak Sanghavi, a pediatric cardiologist and assistant professor of pediatrics at the University of Massachusetts Medical School, scientists and drug companies usually describe the benefits of many medications in terms of relative risks. This is said to "inflate" the benefits of medical therapy. Dr. Sanghavi said there is an alternative statistic that is not used. It's called the "number needed to treat" (or NNT, for short.)

Using cholesterol lowering drug as an example, he recounts the case with Pravachol years ago when it was reported as causing a 31 percent reduction in heart attacks. This caused billions of dollars in sales. By stating the results of clinical trials in terms of "relative risks", it powerfully exaggerates the benefits of drugs and other invasive therapies.

Thirty-one percent fewer heart attacks!

What did the drug manufacturers mean when they talked about a 31 percent relative reduction in heart attacks? Borrowing Dr. Sanghavi's explanation, it meant that "taking Pravachol every day for five years reduced the incidence of heart attacks from 7.5 percent to 5.3 percent. This indeed means that there were 31 percent fewer heart attacks in patients taking the drug. But it also means that the "absolute risk" of a heart attack for any given person dropped by only 2.2 percentage points." So a 31 percent relative reduction in heart attacks equals (or means the same thing as) a 2.2 percent absolute reduction in heart attacks.

So to break this down further, if 100 people with high cholesterol took statins, 93 of them would not have had heart attacks anyway. Of the remaining seven people, five would have heart attacks despite taking Pravachol. Only two out of the original 100 avoided a heart attack by taking the daily pills for five years. This means that in order to prevent 2 people taking Pravachol over a 5-year period from having a heart, we would need to treat 100 of them. In other words, the number needed to treat (NNT) is 50 - fifty needed to be treated in order to observer a reduction in heart attacks.

Can you see what a different picture is created by stating drug research results in terms of relative risk reduction vs. absolute risk reduction? Anybody can see that these 50 people could do much better by changing their diets and getting enough exercise over a period of a few months (not even 5 years!) So the objective of this drug medication for diseases and health conditions resulting from lifestyle habits is ____________________ (you fill in the blanks.)

Did you say 'to make more money'?