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Effects of lowering average or below-average cholesterol

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It has been demonstrated that there is a continuous association between cholesterol levels and the risk of myocardial infarction or death from coronary heart disease. Studies have documented that for middle-aged persons, each 0.6 mmol per L drop in total cholesterol confers about 30 percent less risk of coronary heart disease across a wide range of cholesterol levels. Cholesterol lowering has also been shown to reduce the risk of initial and recurrent coronary heart disease in patients with elevated cholesterol levels. MacMahon and associates of the LIPID Trial Research Group conducted a randomized, double-blind trial to evaluate the effects of cholesterol lowering on carotid atherosclerosis among patients with a history of myocardial infarction or unstable angina and average or below average levels of total cholesterol (from 154 to 270 mg per dL [4 to 7 mmol per L] ).

A total of 522 patients were randomized to treatment with a low-fat diet plus pravastatin (40 mg daily) or with a low-fat diet plus placebo. The mean age of participants at the time of enrollment was 61 years. Before randomization and again after two and four years, ultrasound scans of the right common carotid artery were performed. The choice of this vessel as the primary end point in the trial was based on studies demonstrating the histologic validity of such ultrasound measurements. Total cholesterol was measured at the initial visit and at annual visits thereafter. Additional lipid studies were also performed three years after randomization. The primary study outcome was the change from baseline in carotid wall thickness after two and four years of follow-up. Follow-up data were available from 88 percent of study participants after two years and from 77 percent after four years.

Over the four-year study period, total cholesterol was reduced by an average of 38.6 mg per...