Multiple Risk Factor Intervention Trial

Multiple Risk Factor Intervention Trial
Name	Multiple Risk Factor Intervention Trial
Acronym	MRFIT
Start	1973
End	1982
Country	United States
Sponsor	National Heart, Lung, and Blood Institute
Design	Multicenter randomized trial
Participants	~12,866 men
Primary	Coronary heart disease mortality

Multiple Risk Factor Intervention Trial

The Multiple Risk Factor Intervention Trial was a large-scale prevention trial initiated in the 1970s to evaluate multifactorial strategies for reducing coronary heart disease mortality among high-risk men. Conceived and funded by the National Heart, Lung, and Blood Institute, the trial involved collaboration with prominent institutions including the Centers for Disease Control and Prevention, several academic medical centers, and community health organizations. The study's scale and findings influenced guidelines promulgated by organizations such as the American Heart Association and the World Health Organization.

Background and Objectives

MRFIT was undertaken amid rising attention to cardiovascular disease after influential reports like the Framingham Heart Study highlighted risk factors such as smoking and hypercholesterolemia. Principal objectives included testing whether simultaneous modification of multiple risk factors—cigarette smoking, serum cholesterol, and blood pressure—could reduce mortality from coronary heart disease compared with usual care. Investigators sought to inform policy discussions in venues such as the U.S. Congress, the National Institutes of Health, and advisory committees chaired by figures associated with institutions like the Johns Hopkins Hospital and the Mayo Clinic.

Study Design and Methods

The trial used a randomized, controlled, multicenter design coordinated through field centers including academic affiliates like University of Minnesota, Emory University, and University of Pittsburgh. Eligible men aged 35–57 with elevated risk profiles were identified through screening programs administered in collaboration with entities such as the American Medical Association and labor unions. Randomization allocated participants to an intensive risk factor intervention arm versus usual care, with standardized protocols for measurement developed by committees drawing expertise from investigators who had worked on projects at the Harvard School of Public Health and Stanford University School of Medicine. Endpoints and statistical plans were reviewed by oversight bodies resembling panels convened by the Institute of Medicine.

Participant Characteristics and Recruitment

Approximately 12,866 men were enrolled after screening many thousands via outreach channels that included workplace health programs, local clinics, and partnerships with organizations like the United Auto Workers, Teamsters, and municipal health departments in cities such as Detroit, Chicago, and Los Angeles. Baseline characteristics documented elevated systolic and diastolic blood pressure, high serum total cholesterol, and heavy cigarette use; these profiles were comparable to risk populations studied earlier in cohorts from Framingham, Massachusetts and surveillance activities led by the Public Health Service. Demographic and occupational descriptors echoed populations represented in contemporaneous studies at institutions including Columbia University and Yale University.

Interventions and Implementation

The intensive intervention combined behavioral counseling, pharmacologic treatment, and community-level strategies. Smoking cessation support drew upon approaches promoted by programs at the American Cancer Society and clinics affiliated with Massachusetts General Hospital. Lipid-lowering strategies emphasized dietary modification informed by research from University of California, San Francisco investigators and early pharmacotherapy consistent with emerging work from pharmaceutical collaborators associated with Merck and Pfizer. Hypertension management followed protocols aligned with clinical trials conducted at centers such as Vanderbilt University Medical Center and University of Texas Southwestern Medical Center. Implementation required coordination among primary care networks, occupational health services, and local health departments comparable to those in Cleveland, St. Louis, and Baltimore.

Outcomes and Results

Primary outcome analyses revealed that, despite favorable changes in risk factor levels in the intervention arm, there was no statistically significant reduction in coronary heart disease mortality at the planned follow-up compared with usual care. Secondary findings documented substantial reductions in serum cholesterol and smoking prevalence and improvements in blood pressure control, echoing mechanistic insights from biochemical studies at Massachusetts Institute of Technology and clinical observations at Brigham and Women's Hospital. The trial's data and subsequent reanalyses prompted debate in scientific circles including symposia at Johns Hopkins University and policy discussions involving the Office of Management and Budget and advisory boards to the Surgeon General.

Interpretation and Impact on Clinical Practice

MRFIT influenced interpretation of prevention strategies by demonstrating that risk factor modification at the individual and community levels yields measurable intermediate benefits even when mortality effects are difficult to demonstrate within trial constraints. The trial shaped recommendations from the American College of Cardiology, the British Heart Foundation, and the European Society of Cardiology regarding multifactorial risk management and informed subsequent trials such as the Intervention Project on Coronary Risk Factors and large-scale statin outcome trials at institutions like Oxford University and Imperial College London. The legacy of the trial is visible in guidelines promulgated by bodies including the U.S. Preventive Services Task Force and in prevention programs run by organizations such as Centers for Disease Control and Prevention chronic disease divisions, influencing research agendas at universities like University of California, Los Angeles and public health schools like the Bloomberg School of Public Health.

Category:Clinical trials