A little backgound is called for. My family history suggests that I am at risk for heart attack or stroke. My father's father [the socialist] died of a stroke, my mother's father suffered a debilitating stroke, and my mother died of a heart attack. All of this is compounded by the fact that a good many years ago, I suffered a transient ischemic attack [or TIA, as it is called in the trade], a short-lived mini-stroke. [Readers are free to invoke this fact as explanation for my bizarre beliefs, although I was assured that I recovered competely.] Accordingly, I watch my diet, eat very little salt, exercise, and take various medications designed to lower my blood pressure and cholesterol level. In addition, like millions of other Americans, I take daily what I still refer to as a "baby aspirin," which is to say an 81 mg. tablet.
This morning, I checked in on the UPSHOT, a NYTIMES column for the statistically obsessed. There, I found a fascinating column about medical statistics, which introduced me to the concept of Number Needed to Treat, or NNT. This is the minimum number of persons taking some medication required statistically to account for one cure or disease prevention. Apparently, doctors now know stuff like this, as a result of keeping elaborate records.
The NNT for a baby aspirin is 2000! Here is what the UPSHOT reports:
"According to clinical trials, if about 2,000 people follow these guidelines over a two-year period, one additional first heart attack will be prevented. That doesn’t mean the 1,999 other people have heart attacks. The fact is, on average about 3.6 of them would have a first heart attack regardless of whether they took the aspirin. Even more important, 1,995.4 people would never have a heart attack whether or not they took aspirin. Only one person is actually affected by aspirin. If he takes it, the number of people who remain heart attack-free rises to 1996.4. If he doesn’t, the number remains 1995.4. But for 1,999 of the 2,000 people, aspirin doesn’t make any difference at all."
Needless to say, there is no way of knowing who that single individual is.
I have to say, this gives me pause, although I will continue to take the aspirin, of course. I mean, with my luck, I might just be that one person.
Not sure how they do those stats. It might be that some of those 1,995.4 who wouldn't get a heart attack wouldn't because they got hit by a bus first.
ReplyDeleteThis type of evidence based decision making is really helpful. One of the positive aspects of the Affordable Care Act was the attempt to add more evidence to medicine.
ReplyDeleteThere are countless regular procedures and medicines that have no more effect than leeches on average. Some times that is the effect of "averages" (many orthopedic surgeries have no average effect but everyone goes to Lake Woebegone Surgical Associates), some of these are placebo effects (cough syrup), and many have all the benefits
I am afraid that the prophylactic use of low-dose aspirin is pretty to close to the last scenario. You mention that it has a NNT of 2000 for heart attack (that is actually better for any heart problem--1 in 1667) but failed to mention the risks of major bleeding issues (1 in 3333).
When you let doctor's decide they choose a lot more care than people would if given the information in an understandable way. People, even people who define themselves as "risk-loving", generally avoid ANY treatment/drug/procedure with a possible benefit so low as 1 in 2000 particularly when they see the risk is (admittedly low) 1 in 3333.
I was involved with a project where many people avoided 3 in 10 benefits when there was 1 in 50 harm. Not everyone, of course, but this was for a decision where the doctor would routinely go ahead after saying there are "some" not numerated risks.
That is why those dot diagrams are so important (not everyone thinks in numbers) and helpful.
It is just that they are not so widely used. In general, getting patients more involved goes under the rubric of "patient-centered decision making" but there is a wide difference to actual quality of the material helping patients make decisions.
P.S. I know David Auerbach was joking but yes some people get hit by busses but generally that would be randomized across those taking the aspirin and those not. I would argue that those taking aspirin are marginally more likely to get hit by said bus because they could decide to cross roads while taking said aspirin.
Arghh!!!
ReplyDeleteParagraph 3 should end with\
"and many have all the benefits washed out with all the costs (antibiotic treatment for minor infections, beta-blockers for heart attacks, etc.)"
There are countless regular procedures and medicines that have no more effect than leeches on average.
ReplyDeleteMany years ago, I worked in a hospital in-patient pharmacy as a tech. We actually had leaches that we used from time to time, and they worked quite well for the purposes we used them for - sucking blood. If, say, you have your ear cut off, it's important to keep blood flowing to the ear after it's sown back on. But, that's not super easy on its own. If, however, you stick a few leaches on the ear, they will keep blood flowing to it (and them), because of their sucking and their anti-coagulation saliva (or whatever comes out of a leach mouth.) They are also good for more cosmetic uses, such as making a fresh bruise go away. I expect they are not good for most other things. But for these things, they seemed to be quite useful.