Association of body mass index with long-term outcomes in older adults hospitalized for COVID-19: an observational study

Abstract

Both underweight and obesity have been associated with poor prognosis in COVID-19. In an older populations of patients hospitalized for SARS-CoV-2 infection, we aimed to evaluate the association between body mass index (BMI) and short and long-term prognosis. Among 434 consecutive patients aged ≥ 70 years and hospitalized for suspected COVID-19 at a university hospital, 219 patients (median age of 83 years, 53% male) testing positive for COVID-19 and for whom BMI was recorded at admission, agreed to participate. Among them, 39 had a BMI < 20 kg/m², 73 had a BMI between 20 and 24.9 kg/m² and 107 had a BMI ≥ 25 kg/m². After adjustment for confounders, BMI < 20 kg/m² was associated with a higher risk of one-year mortality (hazard ratio (HR) [95% confidence interval]: 1.75 [1.00-3.05], p = 0.048), while BMI ≥ 25 kg/m² was not (HR: 1.04 [0.64-1.69], p = 0.9). However, BMI was linearly correlated with both in-hospital acute respiratory failure (p = 0.02) and cardiovascular events (p = 0.07). In this cohort of older patients hospitalized for COVID-19, low BMI, rather than high BMI, appears as an independent risk factor for death after COVID-19. The pathophysiological patterns underlying this excess mortality remain to be elucidated.

Figure 1

Flow chart.

Figure 2

Kaplan–Meier curves for 30-day (left) and one-year (right) mortality after hospitalization for COVID-19 according to the body mass index.

Figure 3

Adjusted hazard ratio (aHR) for 30-day (left) and one-year (right) mortality according to the body mass index (BMI, reference group: BMI 20–24.9 kg/m²).