Saturday, November 4, 2017

Statins and Statistics

Guidelines for doctors recommend prescribing cholesterol medication for patients who show a ten percent (or even lower) chance of developing heart disease over the next ten years by the most recent approved measure. When I first heard about this it struck me as odd, even absurd: another case of a hammer seeing everything as a nail. For doctors, all of us are only varying degrees of sick, and hence in need of treatment, since we are never perfectly healthy, right? But how could 10 percent be something to worry about? Isn’t it intuitive that something is probable only if it's >50 percent? And 10 percent is so far below that that it seems downright improbable.

    But then I thought about it in a different way: Suppose someone handed you a revolver with ten chambers in the cylinder and a bullet in one of them. Would you be willing to play Russian roulette?

    Or suppose you were one of ten people in a room, one of whom was to be chosen at random to be killed (or be given a stroke, the way experimenters induce them in lab animals). Would you feel comfortable?

    I think those ways of thinking about it make ten percent appear to be far from negligible.

    Another way to enhance the impression is to imagine a room with 100 people in it. To be told that 10 of them would soon die seems significant indeed, doesn’t it?

    Or that of a crowd of 1000 people, 100 would be killed or severely injured. Begins to sound a lot like what just happened in Las Vegas, eh? (speaking of odds, aptly enough).

    Part of what is going on here with these Gestalt shifts of risk is that risk consists in not just probability but probability times magnitude of the outcome. In this case the outcome is heart attack, stroke, or death. If we were just talking about a ten percent chance of losing 5 cents, we would say the risk is negligible. But if the risk is losing your life (or lifestyle), then the same probability yields a much higher risk.

    So my initial impression of risk was based on a fallacious conflating of risk with just probability, discounting the magnitude of the outcome. In other words, I was considering only a number, a statistic, in the abstract, and not its concrete application, in this case, to heart disease.

    Of course, none of this predicts in the individual case. Also, there must be countless variables not taken into consideration. Consider also that any medication taken to ameliorate the condition brings its own bevy of risks. Finally, the drugs are hardly likely to guarantee their intended results, and may in fact be efficacious in only a small percentage of cases. (Thank you, Mitchell Silver, for that last point ... who also adds a further point: The severity of the heart disease in question needs to be specified, since in theory it could cover a range from severe to negligible.)

    This is why, in the end, treatment (if any) is what is commonly called a matter of judgment ... and also preferences. So presented with the facts as stated -- let's say, 10-percent of folks like you (in some but of course not all respects) will (untreated, I presume....?) likely develop heart disease of such-and-such range of severity in the next ten years, and Medication X has been shown to avert or at least ameliorate heart disease in n percent of such cases, but also poses such-and-such risk of so-and-so side effects -- should your doctor prescribe or should you take the med? I think there's no "should" about it. The only question is: What will you do once you have reflected on the relevant facts?

Addendum 1
Here's another way to think about the recommendation to take a statin if there is a ten percent chance you will develop heart disease in the next ten years. It is telling doctors to, in effect, shove pills down the throats of ninety percent of people fitting the profile even though they don't need it, and even though the pills will bring risks of their own, as well as various inconvenient and unpleasant side effects for many who take it (and not to mention that the pills will not be effective even for all of the ten percent who will develop heart disease if they take nothing). 

     The pro-pill folk can reply that there are many situations like this, for example, insurance, where the many subsidize the few since all are at risk but only an unknown few will actually be struck (by disease, fire, theft, accident, lawsuit, etc.). The anti-pill folk can reply that the "premium" in the case of statins may be too high for the individual (or even the society) to afford or be comfortable with (given its risks, possible incommodiousness, or cost), not to mention that the “insurance company” will “cover your loss” in only a percentage of the cases (since the drug is not 100 percent effective). The pro-pill folk can reply that the relatively high likelihood (ten percent for heart disease, as opposed to something minuscule for, say, your house burning down) justifies the (possibly) significant “premium.”

Addendum 2
A more expansive objection to taking a statin is that the drug is an arbitrary intervention. Given that life itself is fraught with every kind of risk, from choking on your food to being incinerated by an asteroid, and it just so happens (no, not “just so happens”; somebody saw the potential for financial profit in this) that people have found a way to ameliorate this particular one (risk of heart disease), we are now expected to avail ourselves of statins. But carried to the extreme, every aspect of our lives could become circumscribed by preventative measures. Indeed, this is already the case -- hence playgrounds with umpteen safety features and ringed by barbed wire with armed guards surrounding them. Thus, the quality of life suffers the more we orient to the avoidance of risk, to the point of absurdity.

            But the pro-statin contingent has an answer to this too. The above argument smacks of an archaic conservatism: “If man were meant to fly ….” Human beings have not lived in their “natural” state since forever. Today we live, on average, longer than ever. It is only natural, in an extended sense, therefore, that we may rely on artificial supplements to maintain our “unnatural” lifespan and good health. Granted, this can be taken to extremes; but so can anything. So here as everywhere, “All things in moderation.” It seems reasonable not to smoke, to wear a seatbelt, to make sure you get exercise regularly, to come inside if there is lightning, to get a flu shot, and so forth. Similarly for taking statins. It doesn’t mean you have to hide under the covers all the time (which would surely bring its own risks!). Judge each case on its merits.

Addendum 3.
Your move.