Multiple Risk Factor Intervention Trial (MRFIT)

The Multiple Risk Factor Intervention Trial (MRFIT) was a randomized controlled trial on primary prevention of coronary heart disease (CHD) death in men with elevated blood pressure (BP), serum cholesterol, and/or smoking habit. In all, 361,662 men were screened in 18 U.S. cities; 12,866 men were randomized to multifactor Special Intervention (SI) or Usual Care (UC). With a 7 year average follow-up, the CHD death rate was 7.1% lower for SI than UC [relative difference in proportion dead; 90% CI (−15%, 25%)]. UC men made more extensive risk factor reductions than anticipated in trial design, and the number of UC deaths was substantially smaller than expected. This result led to an underpowered comparison. Post-hoc assessments showed significantly lower rates of combined morbidity/mortality outcomes for SI than UC. Other findings from MRFIT substantially changed the treatment of hypertension, and long-term epidemiologic follow-up of all 361,662 screenees yielded important findings of great impact on major public health and medical care issues.