Heart Rate at Rest, Exercise Capacity, and Mortality Risk in Veterans

Abstract

Heart rate (HR) at rest has been associated inversely with mortality risk. However, fitness is inversely associated with mortality risk and both increased fitness and β-blockade therapy affect HR at rest. Thus, both fitness and β-blockade therapy should be considered when HR at rest-mortality risk association is assessed. From 1986 to 2011, we assessed HR at rest, fitness, and mortality in 18,462 veterans (mean age = 58 ± 11 years) undergoing a stress test. During a median follow-up period of 10 years (211,398 person-years), 5,100 died, at an average annual mortality of 24.1 events/1,000 person-years. After adjusting for age, body mass index, cardiac risk factors, medication, and exercise capacity, we noted approximately 11% increase in risk for each 10 heart beats. To assess the risk in a wide and clinically relevant spectrum, we established 6 HR at rest categories per 10 heart beat intervals ranging from <60 to ≥100 beats. Mortality risk was significantly elevated at a HR at rest of ≥70 beats/min (hazard ratio 1.14, confidence interval 1.04 to 1.25; p <0.006) and increased progressively to 49% (hazard ratio 1.49, confidence interval 1.29 to 1.73; p <0.001) for those with a HR at rest of ≥100 beats/min. Similar trends were noted when for subjects aged <60 and ≥60 years and those treated with β blockers. In all assessments, mortality risk was consistently overestimated when fitness was not considered. In conclusion, HR at rest-mortality risk association was direct and independent. A progressive increase in risk was noted >70 beats/min for the entire cohort, those treated with β blockers, and those aged <60 and ≥60 years. Mortality risk was overestimated slightly when fitness status was not considered.