The Secret Statistic

There's one medical statistic doctors don't much talk about despite it's importance. It's called "number needed to treat," or NNT. It's measure developed in the past 20 years, and it's one of the best-kept statistical secrets in medicine.
The idea of NNT is simple enough. Most clinical trials look at how much better people do on a particular medicine. NNT answers the question: how many people have to take a particular drug to avoid one incidence of a medical issue (such as heart attack, or recurrence of cancer)? For example, if a drug had an NNT of 50 for heart attacks, then 50 people have to take the drug in order to prevent one heart attack. That doesn't sound like a lot, so pharmaceutical companies tend to keep the number quiet and focus on broader, U.S. population-based statistics. But that could be changed if you ask for the NNT up front the next time you're handed a prescription.

When the NNT statistic was first developed in 1988, it was intended to help you make a decision about whether or not to take a drug. After all, having it put in simple terms such as "out of every 50 people who take this drug, perhaps one heart attack will be prevented, and the other 49 will receive no benefit," puts things into perspective...a perspective that the drug companies do not want you to see. One of the most blatant examples of how drug companies have hidden NNT for their own self-serving purposes lies with cholesterol drugs. These drugs, which can cause side effects like liver damage, muscle weakness, cognitive impairment and many side effects like liver damage, muscle weakness, cognitive impairment and many others, are touted as miracle pills that can slash your risk of a heart attack by more than one third.
Well, "business week" actually did a story on this very topic earlier this year, and they found the real numbers right on Pfizer's own newspaper ad for the cholesterol lowering drug "Lipitor."
Upon first glance, the ad boasts that Lipitor reduces heart attacks by 36 percent. But there is an asterisk. And when you follow the asterisk, you find the following in much smaller type: "That means in a large clinical study, 3% of patients taking a sugar pill or placebo had a heart attack compared to 2% of patients taking Lipitor/"
What this means is that for every 100 people  who took the drug over 3.3 years, three people on placebos, and two people on Lipitor, had heart attacks. That means that taking Lipitor resulted in just one fewer heart attacks  per 100 people.
What if you put 250 people in a room and told them they would each pay $1,000 a year for a drug they would heave to take every day, that many would get diarrhea an muscle pain, and that 249 would have no benefit? and that they could do just as well by exercising? How many would take that?