The Effects of Body Mass Index on In-Hospital Mortality and Outcomes in Patients With Heart Failure: A Nationwide Analysis

Background: Heart failure (HF) remains one of the leading causes of death in the United States. While many large-scale studies show a positive relationship between cardiovascular mortality and body mass index (BMI), several studies have also observed lower mortality rates among obese HF patients. Therefore, we sought to assess the impact of BMI on in-hospital outcomes in patients admitted with HF. Methods: Patients hospitalized with congestive heart failure (CHF) diagnosis between 2005 and 2014 were identified from the US National Inpatient Sample database using the International Classification of Diseases, Ninth Revision, Clinical Modification diagnostic and procedural codes. The sample was divided into three groups based on their BMI. In-hospital outcomes were assessed in different groups and sub-groups. Results: We identified 8,674,190 patients admitted with a primary diagnosis of HF, out of which 1.8% had BMI between 30 and 39.9 kg/m(2) and 3.7% had BMI >40 kg/m(2). In-hospital mortality was reported in 5.6% of patients with BMI <30 kg/m(2), compared to 2.3% in those with BMI 30-39.9 kg/m(2) and 3.1% in the group with BMI >40 kg/m(2). After adjusting for various confounders, in-hospital mortality was lower in those with BMI 30-39.9 kg/m(2) than those with BMI <30 kg/m(2) (OR 0.56; CI 0.51-0.62). Similarly, in-hospital mortality was lower in those with BMI >40 kg/m(2) than those with BMI <30 (OR 0.87; CI 0.81-0.92). Conclusion: Even though this study supports the findings of previous smaller studies illustrating the existence of the "obesity paradox" in HF hospitalizations, the pathogenesis behind this paradoxical effect is still unclear.