The HELP-LDL-apheresis multicentre study, an angiographically assessed trial on the role of LDL-apheresis in the secondary prevention of coronary heart disease. II. Final evaluation of the effect of regular treatment on LDL-cholesterol plasma concentrations and the course of coronary heart disease

The 356,222 men aged 35 to 57 years, who were free of a history of hospitalization for myocardial infarction, screened by the Multiple Risk Factor Intervention Trial (MRFIT) in its recruitment effort, constitute the largest cohort with standardized serum cholesterol measurements and long-term mortality follow-up. For each five-year age group, the relationship between serum cholesterol and coronary heart disease (CHD) death rate was continuous, graded, and strong. For the entire group aged 35 to 57 years at entry, the age-adjusted risks of CHD death in cholesterol quintiles 2 through 5 (182 to 202, 203 to 220, 221 to 244, and greater than or equal to 245 mg/dL [4.71 to 5.22, 5.25 to 5.69, 5.72 to 6.31, and greater than or equal to 6.34 mmol/L]) relative to the lowest quintile were 1.29, 1.73, 2.21, and 3.42. Of all CHD deaths, 46% were estimated to be excess deaths attributable to serum cholesterol levels 180 mg/dL or greater (greater than or equal to 4.65 mmol/L), with almost half the excess deaths in serum cholesterol quintiles 2 through 4. The pattern of a continuous, graded, strong relationship between serum cholesterol and six-year age-adjusted CHD death rate prevailed for nonhypertensive nonsmokers, nonhypertensive smokers, hypertensive nonsmokers, and hypertensive smokers. These data of high precision show that the relationship between serum cholesterol and CHD is not a threshold one, with increased risk confined to the two highest quintiles, but rather is a continuously graded one that powerfully affects risk for the great majority of middle-aged American men.

In the Lipid Research Clinics Coronary Primary Prevention Trial (LRC-CPPT), a 19% lower incidence of coronary heart disease (CHD) in cholestyramine-treated men was accompanied by mean falls of 8% and 12% in plasma total (TOTAL-C) and low-density lipoprotein (LDL-C) cholesterol levels relative to levels in placebo-treated men. When the cholestyramine treatment group was analyzed separately, a 19% reduction in CHD risk was also associated with each decrement of 8% in TOTAL-C or 11% in LDL-C levels (P less than .001). Moreover, CHD incidence in men sustaining a fall of 25% in TOTAL-C or 35% in LDL-C levels, typical responses to the prescribed dosage (24 g/day) of cholestyramine resin, was half that of men who remained at pretreatment levels. Adherence to medication was associated with reduced incidence of CHD only when accompanied by falls in TOTAL-C and LDL-C levels. Small increases in high-density lipoprotein cholesterol levels, which accompanied cholestyramine treatment, independently accounted for a 2% reduction in CHD risk. Thus, the reduction of CHD incidence in the cholestyramine group seems to have been mediated chiefly by reduction of TOTAL-C and LDL-C levels.

The Cholesterol-Lowering Atherosclerosis Study (CLAS) was a randomized, placebo-controlled, angiographic trial testing combined colestipol hydrochloride and niacin therapy in 162 nonsmoking men aged 40 to 59 years with previous coronary bypass surgery. During two years of treatment there was a 26% reduction in total plasma cholesterol, a 43% reduction in low-density lipoprotein cholesterol, plus a simultaneous 37% elevation of high-density lipoprotein cholesterol. This resulted in a significant reduction in the average number of lesions per subject that progressed (P less than .03) and the percentage of subjects with new atheroma formation (P less than .03) in native coronary arteries. Also, the percentage of subjects with new lesions (P less than .04) or any adverse change in bypass grafts (P less than .03) was significantly reduced. Deterioration in overall coronary status was significantly less in drug-treated subjects than placebo-treated subjects (P less than .001). Atherosclerosis regression, as indicated by perceptible improvement in overall coronary status, occurred in 16.2% of colestipol-niacin treated vs 2.4% placebo treated (P = .002).