Statins and the number needed to treat

“Do Cholesterol Drugs Do Any Good?” by John Carey. Business Week, 17 January 2008.

I stumbled across this article earlier this week and was intrigued. My bus driver, who I found out last month studies and gives seminars on nutrition, spoke disparagingly about statins, and then I talked at length with a relative over spring break about the medications he takes. I also carry a torch for LDL cholesterol levels insofar as I think it bears too much of the blame for heart disease.

This article focuses on a statistic I’d never heard of before: number needed to treat, or NNT. NNT is the number of people that need to be treated in order for one person to benefit, compared to a control. The lower the NNT, the more effective the treatment. Lipitor’s newspaper ad says in large print "Lipitor reduces the risk of heart attack by 36%...in patients with multiple risk factors for heart disease" and in small print, "3% of patients taking a sugar pill or placebo had a heart attack compared to 2% of patients taking Lipitor." That yields a NNT of 100 as calculated below:

1/(experimental event rate – control event rate) = 1/(0.03-0.02) = 100

This means that you need to treat 100 people with statins in order for one person to benefit. Corey cites the example of the standard antibiotic treatment for H. pylori stomach bacteria, which cause ulcers. Its NNT is 1.1 – treat 11 people and 10 will be cured.

Statins’ high NNT means different things for an individual and a population, according to Dr. Peter Trewby, consultant physician at Darlington Memorial Hospital in Britain.

"It's all about whether we think the population is what matters, in which case we should all be on statins, or the individual, in which case we should not be…What is of great value to the population can be of little benefit to the individual."

The drug companies sure would enjoy having everyone with elevated cholesterol taking a statin. But statins are not cheap or free from side effects. And they only target one parameter, unlike diet and exercise, which can have a positive effect on a number of health indicators.

Cholesterol is handy because it’s relatively easy to measure and track. But it’s just one number. We are assessing our iron status in Experimental Nutrition and are measuring five different parameters in order to get a complete picture. And that’s just for iron. Coronary disease is much more complex and has other risk factors besides elevated LDL-cholesterol levels. So focusing on one number is not a very effective mode of treatment.

That’s not to say that we should ignore LDL cholesterol entirely.

Dr. Ronald M. Krauss, director of atherosclerosis research at the Oakland Research Institute, explains that higher LDL levels do help set the stage for heart disease by contributing to the buildup of plaque in arteries. But something else has to happen before people get heart disease. "When you look at patients with heart disease, their cholesterol levels are not that [much] higher than those without heart disease," he says. Compare countries, for example. Spaniards have LDL levels similar to Americans', but less than half the rate of heart disease. The Swiss have even higher cholesterol levels, but their rates of heart disease are also lower. Australian aborigines have low cholesterol but high rates of heart disease.

The article goes on to explain some biochemistry details that I found interesting. I think need to read more about what statins do. Corey’s layman explanation is that they “work by bollixing up the production of a substance that gets turned into cholesterol.” I can do better than that.

Photo and article found here.