William G. Rothstein Public Health and the Risk Factor, A History of an Uneven Medical Revolution (2003)

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.In 1988, the American Heart Association and the American Col-lege of Cardiology recommended angioplasty for treating angina pectorisin men younger than age 65 without high blood pressure or diabetes, whohad blockage in a small uncalcified single coronary artery.A 1991 commit-tee of the British Cardiac Society recommended angioplasty when the block-ages were discrete, short, proximal enough to be reached by the ballooncatheter, and preferably not in the immediate vicinity of acute bends orlarge side branches. A 1990 study of patients with angina pectoris foundthat coronary artery bypass surgery was superior to drugs where the heart spumping action was weakened by previous myocardial infarctions.21Many specialists disregarded the recommendations and continued topress for the broadest possible use of their own procedures.In 1995 theNew York Times reported that a rancorous debate over the benefits ofangioplasty and thrombolytic drugs divided cardiologists at the annualmeeting of the American College of Cardiology.A 1994 recommendationconcerning emergency room treatment of myocardial infarction was de-signed partly to eliminate jurisdictional battles and disputes among emer-gency doctors, cardiologists, internists, family doctors, and other medicalspecialists who compete to care for heart attack patients, according to anarticle in the New York Times.The economic stakes were enormous: in themid-1990s coronary artery bypass surgery was the most frequently per-formed major operation in the country and cardiologists who performedangioplasties earned considerably more than other cardiologists.22Surgeons and cardiologists also extended the use of coronary arterybypass surgery and angioplasty to the very old, who had previously beenconsidered unsuitable for such aggressive interventions.The new policywas justified by improvements in the procedures and the risks of no treat-ment, but another factor was the availability of fewer younger patients as294 Risk Factors and Coronary Heart Diseasecoronary heart disease rates declined.A 1994 study concluded that bothprocedures were often performed on elderly persons who could have beentreated as effectively and much more safely with drugs.23Thus the atherosclerosis theory emerged as the primary basis for thetreatment of serious coronary heart disease.It had equally significant con-sequences for the prevention of all forms of coronary heart disease.17THE DIET-HEART HYPOTHESISThis is a time when great pressure is being put on physicians to dosomething about the reported increased death rate from heart attacksin relatively young people.People want to know whether they are eat-ing themselves into premature heart disease.(Nutrition Committee, American Heart Association, 1957)1The diet-heart or lipid hypothesis, based on the atherosclerosis theory of coro-nary heart disease, consists of a sequence of events involving dietary cholesteroland fats, blood cholesterol, atherosclerosis, and ultimately coronary heart dis-ease.The most rigorous statistical studies have shown very weak or nonexistentrelationships between diet or blood cholesterol and coronary heart disease.Blood Cholesterol Levels andCoronary Heart Disease RatesThe underlying factor in the atherosclerosis theory of coronary heart dis-ease is cholesterol in the human body.Cholesterol is found in all cell mem-branes and is especially prevalent in organs like the brain, liver, and kid-neys; it plays a key role in the production of some hormones, steroids, andvitamin D; and it is converted to bile that is essential for digestion.Choles-295296 Risk Factors and Coronary Heart Diseaseterol tends to accumulate in atheromas because it is a lipid, a fatty or greasycompound that does not dissolve in water or blood and so cannot be re-moved by circulating blood.Cholesterol was identified and labeled in the earlynineteenth century and its presence in atheromas was noted a century later.Cholesterol in the human body is obtained from both external andinternal sources.About one-third of the cholesterol found in the intestinecomes from the consumption of animal foods, primarily meat, eggs, anddairy products.Two-thirds comes from internal synthesis in the intestinesand liver.The human body regulates the total amount of its blood choles-terol by balancing internal synthesis and dietary intake.2Cholesterol is transported from its sources in the intestine and liverto cells by flowing through the blood as lipoproteins, a soluble chemicalcombination of cholesterol and certain proteins.About 1950 John Gofmanand his coworkers differentiated several types of lipoproteins according totheir densities.The low density lipoproteins (LDL) transport 60% 70%of the cholesterol through the blood, the high density lipoproteins (HDL)transport 20% 30%, and the very low density lipoproteins (VLDL) trans-port 10% 15%.LDL contain 40% 45% cholesterol, VLDL contain 10%20%, and HDL contain 18%.Each type of lipoprotein also contains vary-ing amounts of protein and two other lipids, triglycerides and phospholipids.HDL is believed to remove excess cholesterol from the blood, but the evi-dence has been inconclusive.3The atherosclerosis theory of coronary heart disease consists of a threestep process: high levels of cholesterol in the blood lead to its accumulation inthe arteries as atherosclerosis, which in turn increases the risk of coronary heartdisease.The theory is therefore based on three statistical correlations.One isthe correlation between the level of blood cholesterol and the amount of ath-erosclerosis in the arteries.which has been supported by autopsy studies.Thesecond is the correlation between the amount of atherosclerosis in the arteriesand coronary heart disease, which has also been supported by autopsy studies.4The third correlation, between blood cholesterol levels and coronaryheart disease rates, is an indirect relationship.According to statistical theory,indirect relationship always have weaker correlations than direct relation-ships.In this case, it is because atherosclerosis is produced by many factorsbesides blood cholesterol levels and coronary heart disease is produced bymany factors besides atherosclerosis.The relationship between blood cholesterol and coronary heart dis-ease was examined in a number of prospective epidemiological studies thatmeasured the blood cholesterol levels in a sample, followed the sample fora period of time, and compared the coronary heart disease rates of personsThe Diet-Heart Hypothesis 297with different blood cholesterol levels.The pathbreaking and most rigor-ous study was the Framingham heart study [ Pobierz całość w formacie PDF ]

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