Abstract 56: Change in Midlife Fitness is an Independent Predictor of Heart Failure in Older Age

Background: Low mid-life fitness is associated with increased risk for heart failure (HF) events decades later. However, the association between changes in mid-life fitness and heart failure risk has not been studied. Methods: We included 9050 subjects (15% Females, mean age 48 years) with no prior cardiovascular disease who underwent two cardiorespiratory fitness measurements approximately 8 years apart. Fitness was estimated in metabolic equivalents (METs) according to Balke treadmill time, with low fitness defined as the lowest quintile of fitness and high fitness defined as quintiles 2-5. Change in fitness was defined categorically according to fitness quintiles (see figure legend) and continuously as the change in METs between the two examinations. Baseline data from the CCLS were matched with Medicare administrative claims data from the Center for Medicare and Medicaid Services. Hospitalization for HF was determined from Medicare claims files. The association between change in fitness and HF hospitalization was assessed by applying a proportional hazard recurrent events model to the failure time data and adjusted for traditional risk factors. Results: After 60,635 person years of Medicare follow up, we observed 242 hospitalizations for HF. Compared to individuals with persistently low fitness levels in middle-age, individuals who increased their fitness levels had a lower rate of HF hospitalization (0.88 vs. 0.64%/year). After multivariable adjustment for baseline fitness level and other risk factors, each 1 MET increase in middle age fitness was associated with 5% less risk for HF hospitalization in later life [HR 0.95 (0.93-0.97) per MET]. Conclusion: Change in mid-life fitness is associated with HF risk in older age. These findings suggest that the heart failure risk related to low fitness may be modifiable with exercise training.