Association of Neutrophil-to-Lymphocyte Ratio with Disease Severity and Clinical Outcomes in COPD: A Retrospective Study Based on GOLD 2025 Classification

Objective: Chronic obstructive pulmonary disease (COPD) is a progressive disorder characterized by systemic inflammation. The neutrophil-to-lymphocyte ratio (NLR) has emerged as an easily accessible biomarker reflecting inflammatory burden. This study aimed to investigate the association between NLR and objective and clinical indicators of COPD severity.Methods: In this retrospective observational study, 127 patients with COPD were included. Clinical and laboratory data were collected between January 2017 and July 2017 using a structured patient evaluation form developed for the study and were retrospectively analyzed. mMRC dyspnea scores and exacerbation histories were recorded at the time of assessment, and exacerbation frequency was determined based on the number of exacerbations requiring hospitalization within the previous year. Patients were subsequently reclassified according to the GOLD 2025 A–B–E grouping system based on the available clinical data. Correlation and group comparison analyses were performed to evaluate the associations between NLR and clinical indicators of COPD severity.Results: NLR was significantly higher in patients with severe disease characteristics, including frequent exacerbations, long-term oxygen therapy (LTOT) requirement, and classification in GOLD Group E (p = 0.001). A significant negative correlation was observed between NLR and %FEV₁ (r = -0.215, p = 0.015). Although NLR showed a statistically significant association with mMRC dyspnea scores, this association was weak. No significant associations were found between NLR and age, sex, body mass index, or smoking status.Conclusion: NLR is significantly associated with objective indicators of COPD severity, particularly airflow limitation, exacerbation burden, and GOLD 2025 classification. Its weak association with subjective symptom scores suggests that NLR may better reflect systemic inflammatory burden than symptom-based assessments. Given its low cost and widespread availability, NLR may serve as a practical complementary biomarker in the clinical evaluation of COPD.