Medical Treatments – Potential for Benefit and Harm

This email isn’t directly related to caregiving or any neurological disorder, but the thought-provoking articles about being a good healthcare consumer are worth sharing.  I found that reading these articles required attention; they probably aren’t meant to be read by stressed-out caregivers.

“The Upshot” is a New York Times blog that covers public policy issues.


Last Monday, there was a blog post about whether a given medical treatment can help someone.  The basic point is that “many fewer people benefit from medical therapies than we tend to think.” See:

There is a metric known as the NNT or number needed to treat. “An N.N.T. of one would mean every person treated improves and every person not treated fails to, which is how we tend to think most therapies work.  What may surprise you is that N.N.T.s are often much higher than one. Double- and even triple-digit N.N.T.s are common.”  I don’t think most of us are aware of this.

The article reviews several examples.

Example #1 – daily aspirin for heart attack prevention.  The NNT is 2,000.  “According to clinical trials, if about 2,000 people [take a daily aspirin] over a two-year period, one additional first heart attack will be prevented. … Of course, nobody knows if they’re the lucky one for whom aspirin is helpful. So, if aspirin is cheap and doesn’t cause much harm, it might be worth taking, even if the chances of benefit are small. But this already reflects a trade-off we rarely consider rationally.”  The authors note that “N.N.T.s as calculated from clinical trial data are probably lower than those based on real-world medical care, not higher.”

Example #2 – Mediterranean diet for heart attack prevention.  The NNT is either 61 or 30, depending on which group you are considering.  “In people who have never had a heart attack, but who are at risk, the N.N.T. is 61 to avoid a heart attack, stroke or death. And that is for people who adhere to the diet for about five years. For those at higher risk, who have already had a heart attack, to avoid one additional death, the N.N.T. is about 30. That’s the number of people who would have to adhere to the diet for four years…”

The authors point out that an NNT of 30 is “pretty good.”  But they go on to say:  “When you hear that the diet prevents heart attacks, then it might sound worth it. But does it still sound worth it when you consider that 29 out of 30 people who stick to the diet for several years see no benefit at all? Will you stick to it for years and be the lucky one for whom that matters?”


Two clinical researchers have put together a website of NNT data from clinical trials.  You can take a short tour of the reviews here:

Or see a list of the reviews, organized by specialty, here:

Each treatment is rated as to whether the benefits outweigh the harms, or vice versa.


Tomorrow’s blog post is about a complementary number – the NNH or number needed to harm.  See:

Back to our aspirin for heart attack prevention example:

Example #3“[The] N.N.T. for aspirin to prevent one additional heart attack over two years is 2,000. Even though this means that you have less than a 0.1 percent chance of seeing a benefit, you might think it’s worth it. After all, it’s just an aspirin. What harm could it do?  But aspirin can cause a number of problems, including increasing the chance of bleeding in the head or gastrointestinal tract. Not everyone who takes aspirin will bleed. Moreover, some people will bleed whether or not they take aspirin.  Aspirin’s N.N.H. for such major bleeding events is 3,333. … Granted, one out of 3,333 is a pretty tiny risk. But remember that the chance of benefit is pretty small, too.”

The authors encourage us to consider the NNT and NNH when making decisions about medical treatment for ourselves or others.