Abstract 18564: The Interaction of Age and Exercise Capacity in the Prediction of All-Cause Mortality: Data From the FIT Project

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Background: Cardiorespiratory fitness, measured clinically as exercise capacity, is a strong predictor of survival. We investigated whether this favorable prognosis is consistent across age groups, particularly in the young and the elderly. Methods: This retrospective cohort study included 56,592 patients without known CAD or CHF (median age 53 years old, 51% men, 64% Caucasian) who underwent clinical treadmill stress testing at Henry Ford Hospital between 1991 and 2009. Patients were followed 11.1 ± 4.6 years for the occurrence of all-cause mortality assessed via search of the Death Master File. We first calculated median METS attained on the treadmill by age decile. Then in multivariable models within each age decile, we assessed the prognostic value of: 1) METS above/below median for age; 2) METS by category; and 3) METS as a continuous variable. Models were adjusted for age (continuous), sex, race, SBP/DBP, hypertension, hyperlipidemia, smoking, diabetes, family history of CAD, obesity, COPD and cardiovascular medication use, and indication for stress test. Results: Median METS decreased with age, from 13 for patients 80 (p<0.001). Older patients were less likely to achieve target heart rate (p<0.001). There were 6,105 deaths during follow-up. By any measure, increasing exercise capacity was a powerful predictor of survival across all age deciles, although there was an interaction with age (Figure). The relative reduction with increasing fitness was greatest in younger patients and decreased with age. The absolute risk reduction was greatest in older patients. Conclusion: Improved cardiorespiratory fitness - as assess clinically by improved exercise capacity - is a powerful predictor of survival across all age groups, although an interaction exists with age. Younger patients have a greater relative reduction in mortality with increasing fitness, while older patients have a greater absolute reduction in mortality.