High percent body fat mass predicts lower risk of cardiac events in patients with heart failure: an explanation of the obesity paradox

BackgroundAlthough high body mass index (BMI) is a risk factor of heart failure (HF), HF patients with a higher BMI had a lower mortality rate than that in HF patients with normal or lower BMI, a phenomenon that has been termed the "obesity paradox". However, the relationship between body composition, i.e., fat or muscle mass, and clinical outcome in HF remains unclear.MethodsWe retrospectively analyzed data for 198 consecutive HF patients (76years of age; males, 49%). Patients who were admitted to our institute for diagnosis and management of HF and received a dual-energy X-ray absorptiometry scan were included regardless of left ventricular ejection fraction (LVEF) categories. Muscle wasting was defined as appendicular skeletal muscle mass index <7.0kg/m(2) in males and<5.4kg/m(2) in females. Increased percent body fat mass (increased FM) was defined as percent body fat >25% in males and>30% in females.ResultsThe median age of the patients was 76years (interquartile range [IQR], 67-82years) and 49% of them were male. The median LVEF was 47% (IQR, 33-63%) and 33% of the patients had heart failure with reduced ejection fraction. Increased FM and muscle wasting were observed in 58 and 67% of the enrolled patients, respectively. During a 180-day follow-up period, 32 patients (16%) had cardiac events defined as cardiac death or readmission by worsening HF or arrhythmia. Kaplan-Meier survival curves showed that patients with increased FM had a lower cardiac event rate than did patients without increased FM (11.4% vs. 22.6%, p=0.03). Kaplan-Meier curves of cardiac event rates did not differ between patients with and those without muscle wasting (16.5% vs. 15.4%, p=0.93). In multivariate Cox regression analyses, increased FM was independently associated with lower cardiac event rates (hazard ratio: 0.45, 95% confidence interval: 0.22-0.93) after adjustment for age, sex, diabetes, muscle wasting, and renal function.ConclusionsHigh percent body fat mass is associated with lower risk of short-term cardiac events in HF patients.