Abstract MP25: Obesity, Heart Failure Risk & Cardiorespiratory Fitness

Introduction: Obesity, defined as body mass index (BMI) ≥30 kg/m 2 , is associated with increased incidence of heart failure (HF). Increased cardiorespiratory fitness (CRF), as indicated by increased exercise capacity, is associated with lower risk of cardiovascular disease and HF. However, the CRF-BMI-HF interaction has not been fully explored. Hypothesis: We assessed the hypothesis that the risk of HF associated with increased BMI is moderated by increased CRF. Methods: We identified 19,881 Veterans (mean age: 58.0±11.3 years) who completed an exercise tolerance test (ETT) to assess either CRF status or suspected ischemia at two VA Medical Centers (Washington DC and Palo Alto, CA). None had documented HF at baseline or evidence of ischemia during the ETT. We established four BMI categories: <25 kg/m 2 ; 25-29.9 kg/m 2 ; 30-34.9 kg/m 2 ; and ≥35 kg/m 2 . In addition, we established four CRF categories based on age-stratified quartiles of peak metabolic equivalents (METs) achieved (mean ± SD): Least-Fit (4.5±1.2 METs; n=4,743); Low-Fit (6.6±1.3; n=5,103); Moderate-Fit (8.0±1.3 METs; n=5,084); and High-Fit (11.1±2.4 METs; n=4,951). Multivariable Cox models were used to estimate hazard ratios (HR) and 95% confidence intervals [CI] for incidence of HF across BMI categories for the entire cohort, using BMI 25-29.9 kg/m 2 (lowest HF rate) as the reference group. We then stratified the cohort by the four BMI categories and assessed HF risk across CRF categories within each stratum, using the Least-fit category as the reference group. The models were adjusted for age, race, gender, cardiac risk factors, sleep apnea, alcohol dependence, medications. Results: During follow-up (median=11.8 years), 2,193 developed HF (10.5 per 1,000 person-years of follow-up). The HF risk for normal weight individuals (18.5-24.9 kg/m2) was 10% higher (p=0.93). For obese individuals, the HF risk was 22% higher in those with BMI 30-34.9 kg/m 2 (HR=1.22; 95% CI: 1.09-1.35) and 50% higher (HR=1.50, 95% CI: 1.32-1.72) for those with BMI ≥35 kg/m 2 . When CRF (peak METs achieved) was introduced in the model, the risk for those with BMI 30-34.9 was reduced from 22% to 16% (HR=1.16; 95% CI: 1.04-1.29) and from 50% to 29% (HR=1.29; 95% CI: 1.13-1.48) among those with ≥35 kg/m 2 . For every 1-MET increase in exercise capacity, HF risk was 15% lower (HR=0.85; 95% CI: 0.83-0.87). We then assessed the impact of CRF on the risk of HF within each of the four BMI categories. The HF risk declined progressively (range: 25% to 69%; p<0.01) with increasing fitness within all BMI categories. Conclusions: The obesity-associated increased risk of HF was attenuated by increased CRF. The HF risk was progressively decreased with increased CRF within all BMI categories.