Results of a multicenter randomized clinical trial of exercise and long-term survival in myocardial infarction patients: the National Exercise and Heart Disease Project (NEHDP)

Abstract

Background: This study examined whether a supervised exercise program improved 19-year survival in 30- to 64-year-old male myocardial infarction patients.

Methods and results: The men (n=651) were participants in the National Exercise and Heart Disease Project, a 3-year multicenter randomized clinical trial conducted in the United States (1976-1979). The treatment group (n=315) exercised for 8 weeks in a laboratory. Thereafter, they jogged, cycled, or swam in a gymnasium/pool setting guided by an individualized target heart rate. Participants in the control group (n=319) were to maintain normal routines but not participate in any regular exercise program. Participants were followed up until their death or December 31, 1995. Cox proportional hazards analysis revealed the all-cause mortality risk estimates (95% CIs) in the exercise group compared with controls to be 0.69 (0.39 to 1.25) after an average follow-up of 3 years, 0.84 (0.55 to 1.28) after 5 years, 0.95 (0.71 to 1.29) after 10 years, 1.02 (0.79 to 1.32) after 15 years, and 1.09 (0.87 to 1. 36) after 19 years. Cardiovascular disease (CVD) mortality risk estimates (95% CI) for the same follow-up periods were 0.73 (0.37 to 1.43), 0.98 (0.60 to 1.61), 1.21 (0.79 to 1.60), 1.14 (0.84 to 1.54), and 1.16 (0.88 to 1.52). However, each 1-MET increase in work capacity from baseline to the end of the original trial resulted in consistent reductions in all-cause and CVD mortality risk at each follow-up period, regardless of initial work-capacity level.

Conclusions: These findings indicate exercise-program participation resulted in nonsignificantly reduced mortality risks early in the follow-up period. Benefits diminished as time since participation increased, which suggests that the protective mechanisms associated with the program may be short term. Contamination between groups over time could also explain the diminished effects, because increased work capacity provided survival benefits up to 19 years.