Friday, January 18, 2008

The Statin Lottery: Number Needed to Treat Statistic

Suppose I invited you to join this contest:
250 people are recruited to participate in the contest. Each person gives me $1,000 and after 1 year one person in the group--selected at random--will receive $250,000 (250 people x $1,000). I keep the interest earned.
Would you participate?

That's similar to the wager that people who are taking statins like Lipitor are engaged in according to Dr. Jerome R. Hoffman, professor of clinical medicine at the University of California at Los Angeles, who was quoted in a recent BusinessWeek article (see "Do Cholesterol Drugs Do Any Good?").

He based his analysis of statins on a little-known but useful statistic, the number needed to treat (or NNT). Here's how to calculate the NNT for Lipitor based on Pfizer's claim in those Jarvik-endorsed Lipitor ads: "Lipitor reduces the risk of heart attack by patients with multiple risk factors for heart disease."

Here's what that means in terms of NNT:
"...for every 100 people in the [Lipitor] trial, which lasted 3 1/3 years, three people on placebos and two people on Lipitor had heart attacks. The difference credited to the drug? One fewer heart attack per 100 people. So to spare one person a heart attack, 100 people had to take Lipitor for more than three years. The other 99 got no measurable benefit. Or to put it in terms of a little-known but useful statistic, the number needed to treat (or NNT) for one person to benefit is 100."
But that's based on one clinical trial involving several hundred or a few thousand high-risk people, not millions of people in the real world. According to the BusinessWeek, "several recent scientific papers peg the NNT for statins at 250 and up for lower-risk patients, even if they take it for five years or more."

BusinessWeek also published this table show NNT statistics for several Rx drug treatments (click to enlarge):

Dr. Hoffman used the Lipitor NNT of 250 statistic to make this analogy:
"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 have to take every day, that many would get diarrhea and muscle pain, and that 249 would have no benefit? And that they could do just as well by exercising? How many would take that?"
Meet me in room 101 and bring your $1,000!


  1. Anonymous10:11 AM

    After reading the article in "Business Week" 1/28/07 about cholesterol drugs and the NNT I am inclined to stop taking Lipitor.
    I now wonder if my stiff neck, stomach discomfort, and difficluly sleeping are connected.

  2. Anonymous4:09 PM

    Yes - statins suck at primary prevention (stopping a patient from having a 1st heart attack or other acute coronary syndrome event) - but please, please let me stress that if you have had a prior MI that statins are a drug you need because statins are reasonably good for secondary prevention (stopping you from having a second MI after you've had one)

  3. I wrote my own little Essay on "Number Needed to Treat" here:


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