Association between Body Mass Index and Hospital Outcomes for COVID-19 Patients: A Nationwide Study

Coronavirus disease 2019 (COVID-19) caused significant morbidity and mortality worldwide. There is limited information describing the hospital outcomes of COVID-19 patients in regard to specific body mass index (BMI) categories.

We utilized the Healthcare Cost and Utilization Project Nationwide Inpatient Sample (NIS) 2020 database to collect information on patients hospitalized for COVID-19 in the United States. Using the International Classification of Diseases, 10th revision, Clinical Modification (ICD-10-CM) coding system, adult patients (≥18 years of age) with a primary hospitalization for COVID-19 were identified. Adjusted analyses were performed to assess for mortality, morbidity, and resource utilization, and compare the outcomes among patients categorized according to BMI.

A total of 305,284 patients were included in this study. Of them, 248,490 had underlying obesity, defined as BMI ≥ 30. The oldest patients were observed to have BMI < 19, while youngest patients were in the BMI > 50 category. BMI < 19 category had the highest crude in-hospital mortality rate. However, after adjusted regression, patients with BMI > 50 (adjusted odds ratio (aOR) 1.63, 95% CI 1.48-1.79, p-value < 0.001) had the highest increased odds, at 63%, of in-hospital mortality compared to all other patients in the study. Patients with BMI > 50 also had the highest increased odds of needing invasive mechanical ventilation (IMV) and mortality associated with IMV compared to all other patient, by 37% and 61%, respectively. Obese patients were noted to have shorter average hospital length of stay (LOS), by 1.07 days, compared to non-obese patients, but there was no significant difference in average hospitalization charges.

Among obese patients primarily hospitalized with COVID-19, those with BMI ≥ 40 had significantly increased rates of all-cause in-hospital mortality, need for IMV, mortality associated with IMV, and septic shock. Overall, obese patients had shorter average hospital LOS, however, did not have significantly higher hospitalization charges.