Multiple Risk Factor Intervention Trial for the Prevention of Coronary Heart Disease (MRFIT)
Multiple Risk Factor Intervention Trial for the Prevention of Coronary Heart Disease (MRFIT)
To determine for a group of men at high risk of death from coronary heart disease whether a
 special intervention program to lower serum cholesterol, reduce blood pressure, and eliminate
 cigarette smoking would result in a significant reduction in mortality from coronary heart
 disease.
BACKGROUND:

 Research findings from prospective epidemiological studies in a number of populations in the
 United States over the past 40 years have convincingly established that elevated blood
 cholesterol, elevated blood pressure, and cigarette smoking are risk factors associated with
 accelerated development of myocardial infarction, sudden death, and death from coronary heart
 disease. These are not the only risk factors associated with premature development of CHD,
 but these factors are modifiable and provide a strong expectation that a reduction of these
 factors should have a beneficial result of reducing the rate of development of premature
 heart attacks.

 A multifactor approach to risk factor reduction closely resembles the type of intervention
 that would be carried out by a physician in his treatment of a patient. The general concept
 for such a trial was endorsed by the Arteriosclerosis Task Force in its 1970 report to the
 Institute.

 Volunteers were selected for the trial through a series of three screening visits, which
 began in November 1973 and were completed by February 28, 1976. From among 361,662 men seen
 at first screening, 12,866 were found to be eligible and were randomized into the trial. Half
 of the participants were assigned to the special intervention group and half to the usual
 care 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. A medical history was taken and a
 physical examination performed. An electrocardiogram was also obtained for centralized
 reading to identify non-fatal myocardial infarction as an additional endpoint.

 Participating in the study were 22 clinical centers across the United States, a coordinating
 center, central laboratory, two ECG reading centers, and lipid standardization laboratory, as
 well as a drug distribution center. The trial has concluded, with the main mortality results
 published in September l982. Active follow-up was terminated on schedule on February 28,
 l982, with final determination of vital status as of that date accomplished for 99.6 percent
 of the study population.

 DESIGN NARRATIVE:

 A randomized, non-blind design with two groups and fixed sample size. The experimental group
 underwent a modified-fat diet, antihypertensive therapy, and education related to lifestyle
 and smoking. Those in the control group were referred to their own physicians for treatment.

 Post-trial mortality surveillance of the 12,300 participants still living at the end of
 active intervention in February 1982 continued through June 1998 under grant support
 (R01HL43232). Use of the National Death Index for mortality surveillance of the 361,662 men
 screened for the MRFIT continued thorough July 1998 under grant support (R01HL28715). Recent
 analyses focus on the relationship of dietary factors, such as sodium, during the trial with
 post-trial mortality. Papers are in progress on further predictors of diabetes mellitus;
 indicators of cardiovascular disease morbidity and risk of death; and prognostic importance
 of changes in indices of left ventricular hypertrophy and ischemia.
Men, ages 35-57. One or more of three risk factors--hypertension, hypercholesterolemia, and
 cigarette smoking.

 Free from coronary heart disease.