Lipid alterations in relation to inflammation and outcome in patients with community-acquired bacterial acute lower respiratory tract infections: A case-control study

Abstract Background Acute infection is associated with alterations in lipid metabolism. We investigated admission lipid profiles in patients hospitalized with acute bacterial lower respiratory tract infections (LRTIs) and their associations with inflammatory biomarkers and outcome. Methods A single-center prospective observational case-control study was conducted at the University Hospital of Patras, Greece, between December 2025 and July 2026, including 233 patients with acute bacterial LRTIs and 100 hospitalized controls frequency-matched for age, sex, and major comorbidities. Total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) were measured within the first 24 hours of admission. Associations with inflammatory biomarkers and survival status were assessed. Multivariable logistic regression analysis included SOFA, neutrophil-to-lymphocyte ratio (NLR), HDL-C, LDL-C, CRP, and TG. Results Patients with LRTIs had higher TG concentrations than controls (126.4 ± 105.3 vs. 98.8 ± 64.2 mg/dL, p = 0.032). HDL-C concentrations were lower, with a borderline between-group difference (34.7 ± 22.5 vs. 41.0 ± 16.3 mg/dL, p = 0.050), whereas TC and LDL-C did not differ significantly. In-hospital mortality in the LRTI group was 24.4% (57/233). Non-survivors had lower HDL-C concentrations than survivors (26.4 ± 17.1 vs. 39.0 ± 22.5 mg/dL, p = 0.001). TC, LDL-C, and TG did not differ significantly by survival status. HDL-C was inversely correlated with C-reactive protein (r = − 0.343, p < 0.001) and lactate (r = − 0.207, p = 0.042). In the multivariable model, only SOFA was significantly associated with in-hospital mortality whereas HDL-C and TG showed inverse associations with mortality, but neither reached statistical significance. Conclusions Acute bacterial LRTIs were associated with higher TG concentrations and a borderline reduction in HDL-C compared to hospitalized controls. Lower admission HDL-C levels were associated with mortality in unadjusted comparisons.