The multiple risk factor intervention trial (MRFIT).

The MRFIT protocol is designed to test the hypothesis that lowering serum cholesterol by diet, reducing high blood pressure by diet and drugs, and cessation of cigarette smoking will result in a reduced risk of death among men aged 35–57 without initial evidence of CHD.

Abstract

The detailed development of the MRFIT protocol is discussed, beginning with the general plan outlined by the National Heart and Lung Institute in the initial solicitation of contract proposals. The protocol is designed to test the hypothesis that lowering serum cholesterol by diet, reducing high blood pressure by diet and drugs, and cessation of cigarette smoking will result in a reduced risk of (a) death from coronary heart disease (CHD), (b) combined fatal CHD and nonfatal myocardial infarction, (c) deaths from all cardiovascular disease, and (d) death from all causes, over a period of 6 years among men aged 35–57 without initial evidence of CHD. After screening 361,662 men, from 1974 to early 1976, 12,866 from the upper end of the risk spectrum of CHD on the basis of serum cholesterol, blood pressure, and smoking habits, were randomly assigned either to a program of Special Intervention (SI) directed toward altering these risk factors or to their usual source of medical care (UC). Men in the UC group have been evaluated once each year in the clinic without direct intervention on the risk factors. Men in the SI group participated in an initial intensive series of group sessions designed to assist in modification of behavior relating to the three risk factors. The SI men have since been invited to the clinic at least three times each year to maintain and increase risk factor change. Changes in the intervention protocol have resulted mainly from difficulty in achieving the expected response in serum cholesterol. These changes have included greater emphasis on control of body weight, the recommendation of more rigorous dietary specifications for those with persistently elevated levels of serum cholesterol, and advice to increase physical activity.