The effect of BMI on COVID-19 outcomes among older patients in South Korea: a nationwide retrospective cohort study*

Background: The coronavirus disease 2019 (COVID-19) pandemic has caused deaths and shortages in medical resources worldwide, making the prediction of patient prognosis and the identification of risk factors very important. Increasing age is already known as one of the main risk factors for poor outcomes, but the effect of body mass index (BMI) on COVID-19 outcomes in older patients has not yet been investigated. Aim: We aimed to determine the effect of BMI on the severity and mortality of COVID-19 among older patients in South Korea. Methods: Data from 1272 COVID-19 patients (≥60 years old) were collected by the Korea Centers for Disease Control and Prevention. The odds ratios (ORs) of severe infection and death in the BMI groups were analyzed by logistic regression adjusted for covariates. Results: The underweight group (BMI<18.5 kg/m(2)) had a higher OR for death (adjusted OR = 2.23, 95% confidence interval [95% CI] = 1.06–4.52) than the normal weight group (BMI, 18.5–22.9 kg/m(2)). Overweight (BMI, 23.0–24.9 kg/m(2)) was associated with lower risks of both severe infection (adjusted OR = 0.55, 95% CI = 0.31–0.94) and death (adjusted OR = 0.50, 95% CI = 0.27–0.91). Conclusions: Underweight was associated with an increased risk of death, and overweight was related to lower risks of severe infection and death in older COVID-19 patients in Korea. However, this study was limited by the lack of availability of some information, including smoking status. KEY MESSAGES: Underweight is an independent risk factor of death in older COVID-19 patients. Overweight patients have a lower risk of death and severe infection than normal-weight patients.