Association of Serum IL-6, TNF-α, and HIF-1α Levels With Respiratory Tract Infection in Patients With Ischemic Stroke

Patients with ischemic stroke are prone to developing respiratory tract infections, which can seriously affect prognosis. The objective of this study was to assess the association of the serum levels of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), and hypoxia-inducible factor-1 alpha (HIF-1α) with the occurrence of respiratory tract infection, and to determine whether these biomarkers are independently associated with infection risk.

A total of 140 patients with ischemic stroke admitted to The Fifth People's Hospital of Jinan between January 2024 and September 2025 were enrolled. Based on the presence or absence of respiratory tract infection, patients were divided into an infection group (n = 41) and a non-infection group (n = 99). Blood samples were collected within 24 hours after admission. Serum IL-6, TNF-α, and HIF-1α levels were measured using enzyme-linked immunosorbent assay (ELISA). Baseline characteristics were compared between the two groups. Point-biserial correlation and univariate logistic regression were used to assess the relationships between inflammatory markers (IL-6, TNF-α, HIF-1α) and respiratory tract infection, followed by multivariate logistic regression to identify independent influencing factors.

There were no significant differences between the two groups in terms of age, gender, body mass index, smoking and drinking history, hypertension, diabetes, coronary heart disease, hyperlipidemia, infarction site, National Institutes of Health Stroke Scale (NIHSS) score, Glasgow Coma Scale (GCS) score, mean respiratory rate, or mean oxygen saturation (p > 0.05). Serum levels of IL-6, TNF-α, and HIF-1α were significantly higher in the infection group than in the non-infection group (p < 0.001). Point-biserial correlation analysis revealed that IL-6, TNF-α, and HIF-1α were positively correlated with respiratory tract infection (r = 0.695, 0.738, and 0.655, respectively; p < 0.001). Univariate logistic regression indicated that all three biomarkers were influencing factors of respiratory tract infection (p < 0.001), and multivariate logistic regression confirmed them as independent influencing factors (p < 0.05).

Elevated serum levels of IL-6, TNF-α, and HIF-1α are significantly associated with respiratory tract infection in patients with ischemic stroke. However, this association does not imply a causal relationship, and the observed increases in these inflammatory markers may reflect a consequence of infection rather than independent risk factors. Early monitoring of these biomarkers may help identify patients with increased risk of developing infection and facilitate timely clinical assessment and intervention to improve outcomes.