Measurement of blood cholesterol concentration is another screening test that has been widely employed without good evidence for its utility. There is no doubt that patients with coronary artery disease (CAD) benefit from the lowering of their blood cholesterol with statin (Lipitor and similar drugs) therapy – so called secondary prevention. But most primary care physicians are treating patients with high blood cholesterol irrespective of whether they have CAD, or for that matter, any other risk factor for the subsequent development of overt vascular disease. Such treatment is called primary prevention, ie the treating of a patient without vascular disease in the expectation that such therapy will prevent or delay the onset of symptomatic disease. Just to be clear – primary prevention aims to prevent something from happening before it happens. Secondary prevention tries to prevent a recurrence of something that has already happened.
Primary prevention of CAD with statin therapy has always been a dubious proposition. First, because there has never been convincing evidence that it works. It’s obvious why such treatment has proved irresistible to most general physicians. We can measure cholesterol. We can give a drug which lowers it. The combination satisfies the need to intervene that is in the DNA of most doctors. The patient is equally satisfied. His cholesterol was high, it goes down, and his insurance pays the cost of the intervention. But there’s another reason that, in the absence of definitive evidence, suggests that such treatment is ineffective. Veins do not get atherosclerosis – only arteries do. Both vessels are exposed to virtually the same metabolic milieu. The only major difference between the two is pressure. Arterialize a vein – graft it into the arterial side of the circulation – and it will develop atherosclerosis. This phenomenon explains why hypertension is such a major risk factor for vascular disease.
Two papers published in the June 28th, 2010 edition of the Archives of Internal Medicine conclude that primary prevention is not beneficial. Cholesterol Lowering, Cardiovascular Diseases, and the Rosuvastatin-JUPITER Controversy and Statins and All-Cause Mortality in High-Risk Primary Prevention. The former says, “The results of the trial (the JUPITER Trial) do not support the use of statin treatment for primary prevention of cardiovascular diseases…” The latter concludes, “This literature-based meta-analysis did not find evidence for the benefit of statin therapy on all-cause mortality in a high-risk primary prevention set-up.”
What should a physician and a patient make of all this? The main lesson is that a high cholesterol by itself is insufficient reason to treat with a statin. If you already have vascular disease statin therapy is definitely indicated. But what if you have at least one additional risk factor for CAD and its like? These include hypertension, family history of early cardiovascular disease, and diabetes. The combination of, say, hypertension and hypercholesterolemia is a bad one. Should such a patient with these two who doesn’t have detectable vascular disease be treated with a statin? The answer suggested by the second of the two papers cited above is no; a physician only has two choices – treat or don’t treat. Right now the best answer is the least satisfying – we’re not sure. Most doctors will likely get out their prescription pad. But if all you have is an isolated lab value take a walk rather than a drug.
The obvious question is why are we routinely measuring cholesterol in patients without vascular disease? The answer like so much else in medicine is that there isn’t a good reason.