Obesity is an Independent Risk Factor for In-Hospital Mortality among Patients Admitted for Heart Failure: A National Study

BackgroundObesity is a major risk factor for developing chronic conditions such as cardiovascular disease and diabetes. However, the phenomenon of "obesity paradox" has been reported over the past two decades which makes the relationship between BMI and inpatient mortality unclear. MethodsThis study identified adult patients (aged 18 years or older) who were admitted to hospitals for the primary cause of heart failure during 2017-2019 from the Healthcare Cost and Utilization Project (HCUP) National Inpatient Sample (NIS) database. Baseline characteristics (i.e., weight status, age, gender, race, Elixhauser score) at the time of admission and the comorbidities were collected. Associations between weight status and in-hospital mortality were examined using logistic regression models that adjusted for individual comorbidities and global risk measures. The likelihood of patients developing each disease comorbidity under different obesity states was examined using logistic regression and the odds were compared across all the disease comorbidities. ResultsThe study identified 204,970 hospital admissions with 4,290 (2.1%) deaths during the hospitalization and 200,680 (97.9%) live discharges. Analysis that did not adjust for individual comorbidities demonstrated the paradox. However, when adjusting for individual comorbidities and global risk measures and compared to the normal-weight patients, those who had higher BMI had an increased risk for in-hospital mortality. BMI of 35-39.9 group had a 26.5% higher likelihood of in-hospital mortality (OR=1.265, 95% CI: 1.066 - 1.503); BMI of 40-69.9 groups was 61.0% to 83.8% higher odds to die in hospital (OR ranged from 1.610 to 1.838, 95% CI varied); patients with a BMI of 70 and above had higher odds of in-hospital mortality (OR=3.144, 95%CI: 2.351 - 4.203). ConclusionObesity is an independent risk factor for in-hospital mortality among patients who were admitted for heart failure. Adjustment for individual comorbidities resolves the obesity paradox. Patients with obesity have a different spectrum of diseases compared to non-obese patients, which may lead to the obesity paradox and bias in the inpatient outcome evaluation. Clinical PerspectiveO_ST_ABSWhat is new?C_ST_ABSO_LIObesity is an independent risk factor for in-hospital mortality. C_LIO_LIIn-hospital mortality increases with the increase in BMI among patients with obesity. C_LIO_LIThe obesity-paradox in in-hospital mortality may be due to the fact that obese patients carry a different spectrum of diseases compared to normal-weight patients, which may bias the health outcomes. C_LI What are the clinical implications?O_LIMaintaining a healthy weight is important in the disease management of patients with congestive heart failure. C_LI Data Availability StatementThe data that support the findings of this study are available from Health Care Cost and Utilization Project (H-CUP) at AHRQ. Restrictions apply to the availability of these data, which were used under approval for this study. Data are available https://hcup-us.ahrq.gov/db/nation/nis/nisdbdocumentation.jsp with the permission of AHRQ.