You wouldn’t think medical professionals would confuse these things, but according to Dalrymple, this is an easier mistake to make than you might think:
The result of the trial was important for itself, for many patients have been treated with niacin on the grounds that it made “sense” to do so; but it was also important because it points to a general lesson, namely that treating statistical markers of disease is not the same as treating disease itself. This should be obvious, but in practice it isn’t. Doctors increasingly treat risk factors as if they were disease, with the result that they could sometimes be doing more harm than good. Of course, there is a long medical tradition of this.