The MRC/BHF Heart Protection Study was much the largest trial in the world of cholesterol-lowering therapy and of antioxidant vitamin supplementation in people at increased risk of heart disease.
Substantial uncertainty had existed about the long-term benefits of cholesterol-lowering drug therapy for particular types of patient, and the extent of its use is limited. Uncertainty as to the possible benefits, or risks, of antioxidant vitamin supplementation was even greater.
To help resolve these uncertainties, the MRC/BHF Heart Protection Study was designed to be really large, to involve a substantial reduction in blood LDL cholesterol levels and a substantial increase in antioxidant vitamin levels, and to include a wide range of patients at substantial risk of death from heart disease and other causes.
Between July 1994 and May 1997, 20,536 individuals were recruited in 69 hospitals from within various prior disease categories (coronary disease, other occlusive arterial disease, diabetes, hypertension) and other categories (women, the elderly, those with average or below average cholesterol levels) where there was uncertainty as to how worthwhile, and safe, are these treatments.
Half of the participants were randomly allocated to receive 40 mg daily simvastatin to lower blood cholesterol levels, and half to receive dummy "placebo" tablets. In addition, within each of these two groups (using a "factorial" design), half were allocated to receive antioxidant vitamins (600 mg E, 250 mg C and 20 mg beta-carotene daily), and half to receive placebo capsules.
Compliance with the study treatments was good, resulting in large average reductions in blood levels of total cholesterol (1.2 mmol/l) and LDL cholesterol (1.0 mmol/l), and large increases in antioxidant vitamin levels. During the scheduled treatment period, there were approximately 4500 major vascular events (which included 2000 coronary events and 1000 strokes) and 3000 deaths (1500 from vascular causes and 1500 from other causes).
Consequently, the MRC/BHF Heart Protection Study provided reliable evidence about the effects of these cholesterol-lowering treatments and antioxidant vitamin supplements on mortality and major morbidity in a wide range of circumstances.
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