Association between body mass index and prognosis of patients hospitalized with heart failure

The prognostic implications of very low body mass index (BMI) values remain unclear in patients with acute decompensated heart failure (ADHF). This study aimed to investigate the prognostic impact of BMI classification based on the World Health Organization criteria in patients with ADHF. Among 3509 patients with ADHF and available BMI data at discharge in 19 participating hospitals in Japan between October 2014 and March 2016, the study population was divided into five groups; (1) Severely underweight: BMI < 16 kg/m², (2) Underweight: BMI ≥ 16 kg/m² and < 18.5 kg/m², (3) Normal weight: BMI ≥ 18.5 kg/m² and < 25 kg/m², (4) Overweight: BMI ≥ 25 kg/m² and < 30 kg/m² (5) Obese: BMI ≥ 30 kg/m². The primary outcome measure was all-cause death. The median follow-up duration was 471 days, with 96.4% follow up at 1-year. The cumulative 1-year incidence of all-cause death was higher in underweight groups, and lower in overweight groups (Severely underweight: 36.3%, Underweight: 23.9%, Normal weight: 14.4%, Overweight: 7.9%, and Obese: 9.0%, P < 0.001). After adjusting confounders, the excess mortality risk remained significant in the severely underweight group (HR, 2.32; 95%CI, 1.83-2.94; P < 0.001), and in the underweight group (HR, 1.31; 95%CI, 1.08-1.59; P = 0.005) relative to the normal weight group, while the lower mortality risk was no longer significant in the overweight group (HR, 0.82; 95%CI, 0.62-1.10; P = 0.18) and in the obese group (HR, 1.09; 95%CI, 0.65-1.85; P = 0.74). Very low BMI was associated with a higher risk for one-year mortality after discharge in patients with ADHF.