Para-Aortic Adipose Tissue and Severe COVID-19: A Retrospective Cross-Sectional Study

Background/Objectives: Obesity is a well-established risk factor for severe COVID-19, largely mediated by chronic inflammation originating from adipose tissue. The role of para-aortic adipose tissue (PAT)—a component of perivascular adipose tissue in COVID-19 severity remains poorly understood. This study aimed to investigate the association between PAT area and the severity of acute SARS-CoV-2 infection, and whether it provides information beyond established clinical and laboratory factors. Methods: This retrospective single-center cohort study included 279 hospitalized patients with confirmed COVID-19 pneumonia. Based on disease severity, patients were divided into moderate and severe groups. PAT area was measured semi-automatically on a single chest CT slice. Sequential multivariable logistic regression models were fitted: Model 1 (PAT alone), Model 2 (PAT + age + sex), Model 3 (primary; PAT + age + sex + BMI), Model 4 (Model 3 + smoking + diabetes + hypertension), and Model 5 (Model 4 + CRP + NLR). Collinearity was assessed using the variance inflation factor (VIF). Effect estimates for PAT were expressed per 0.1 cm2 increase. Results: In the unadjusted model (n = 279), PAT area was associated with severe COVID-19 (OR 1.19 per 0.1 cm2; 95% CI 1.01–1.40; p = 0.038). After adjustment for age and sex, the association was no longer significant (OR 1.10; 95% CI 0.91–1.33; p = 0.325). In the primary model adjusted for age, sex, and BMI (n = 279, with multiple imputation for missing BMI, CRP, and NLR), PAT was not independently associated with severe disease (OR 0.95; 95% CI 0.77–1.17; p = 0.644), while BMI (OR 1.10 per 1 kg/m2; 95% CI 1.04–1.16; p = 0.001), age (OR 1.03; 95% CI 1.01–1.05; p = 0.003), and male sex (OR 1.81; 95% CI 1.00–3.28; p = 0.057) remained associated. The association between PAT and severity was non-linear (p for non-linearity = 0.042). Firth-corrected estimates were virtually identical (OR 0.96; 95% CI 0.79–1.18; p = 0.705), and no influential observations were identified. Conclusions: In this cohort, PAT area measured on a single chest CT slice was not independently associated with severe COVID-19 after adjustment for age, sex, and BMI. The association was non-linear, and the linear estimate was unstable across models due to varying effective sample sizes. BMI, age, and male sex remained the strongest factors. Prospective studies using volumetric or attenuation-based measures of perivascular adipose tissue are needed to clarify its role.