BACKGROUND: Prehypertension is associated with increased risk for mortality, a fact that generated a debate regarding the use of antihypertensive therapy in prehypertensives. Increased exercise capacity is associated with lower mortality risk, but little is known about its effects in prehypertensives. Thus, we evaluated the association between exercise capacity and all-cause mortality in prehypertensives.METHODS: A graded exercise test was performed in 4,478 prehypertensive men at the Veterans Affairs Medical Centers in Washington, DC and Palo Alto, CA. Four fitness categories (quartiles) were defined based on peak metabolic equivalents (METs) achieved. All-cause mortality was assessed for both younger (RESULTS: Exercise capacity was a strong predictor of all-cause mortality, independent of traditional risk factors. The adjusted risk for all-cause mortality was reduced by 15% for every 1-MET increase in exercise capacity in the entire cohort, 18% for younger and 12% for older individuals. Compared to the Very-Low-Fit individuals (10 METs). The trends were similar but more pronounced among younger than older individuals.CONCLUSIONS: A strong, inverse and graded association between exercise capacity and all-cause mortality was observed in prehypertensive individuals. The protective effects of increased fitness were more pronounced in younger than older individuals, suggesting that age should be more closely considered when assessing fitness and mortality relationships.