The Multiple Risk Factor Intervention Trial (MRFIT)

Objectives:

The Multiple Risk Factor Intervention Trial (MRFIT) sought to evaluate the effect of multiple risk factor intervention on mortality from coronary heart disease in high risk men.

Background:

Prospective cohort studies, such as the Framingham Heart Study, had established hypertension, cholesterol, and cigarette smoking as potentially modifiable risk factors for the development of coronary heart disease. A Task Force convened in 1970 determined that a multifactor intervention trial, similar to the approach a physician would utilize, was needed to ascertain whether behavior modification targeting multiple risk factors could potentially reduce mortality from coronary heart disease. A series of screening visits beginning in November of 1973 was used to establish eligibility for the trial. At the first screening visit, blood pressure, cigarette smoking history and cholesterol measurements were obtained to establish risk for CHD. Men were excluded from additional screens if their risk for CHD was low, had diabetes mellitus requiring medication, history of heart attack, serum cholesterol of 350 mg/dL or more, or diastolic pressure of 115 mmHg or more. Measurements taken at the second screen included a resting ECG, medical history, fasting blood draw, and glucose tolerance test. Men were excluded at the second screen based on an ECG determined prior MI, body weight greater than 150% of desirable, angina by Rose questionnaire, untreated symptomatic diabetes, a diet incompatible with the MRFIT food pattern, or lipid lowering treatment. Additional measurements were taken at the third screen and men agreeing to the trial were randomized into either a special intervention group or usual care.

Subjects:

A total of 12,866 men were randomized, roughly half into each group. The special intervention group was advised to follow an eating pattern designed to result in a nutrient intake of 30 percent to 35 percent of calories from fat, with 10 (later 8) percent from saturated and 10 percent from polyunsaturated fat; approximately 300 (later 250) mg of cholesterol; and modification of carbohydrates as needed for individual requirements. This group was also encouraged to cease cigarette smoking by a combination of techniques, including counseling and audio-visual aids. Hypertension management was based on a stepped-care program of weight reduction and drugs similar to that used in the Hypertension Detection and Follow-up Program. Those in the usual care group were referred to their personal physician or other source of care for such management of their risk factors as considered appropriate by these providers. The primary endpoint was death due to coronary heart disease. Men in both the special intervention and usual care groups returned for assessment of changes in risk factor levels annually. The primary endpoint was mortality from coronary heart disease.

Conclusions:

After 6-8 years of followup, risk factor levels declined in both groups but slightly more in the special intervention group. Mortality from coronary heart disease and from all causes was not significantly different among the two groups. (JAMA, 1982; 248:1465-77)