Utility of peripheral blood neutrophil–monocyte to lymphocyte ratio to predict one-year all-cause mortality in patients with chronic obstructive pulmonary disease

Abstract Background Chronic obstructive pulmonary disease is a leading cause of morbidity and mortality worldwide, and reliable, inexpensive biomarkers are needed for improved prognostication. Systemic inflammation contributes significantly to disease progression and adverse outcomes. The neutrophil–monocyte to lymphocyte ratio, derived from routine blood counts, may serve as a practical inflammatory marker. This study aimed to evaluate the association between this ratio and one-year all-cause mortality in hospitalized patients with chronic obstructive pulmonary disease and to examine its relationship with clinical and physiological indicators of disease severity. Methods A retrospective observational cohort study was conducted in the Department of Pulmonary Medicine of a tertiary care center in India. Medical records of 200 adults admitted with spirometry-confirmed chronic obstructive pulmonary disease exacerbation between January 2022 and December 2023 were reviewed. The neutrophil–monocyte to lymphocyte ratio was calculated from admission complete blood counts. Demographic, clinical, spirometric, echocardiographic, and arterial blood gas data were collected. One-year survival status was determined through telephonic follow-up. The primary outcome was one-year all-cause mortality. Associations with body mass index, lung function, pulmonary hypertension, right heart dysfunction, respiratory failure, and exacerbation frequency were also assessed. Statistical analyses included group comparisons, correlation testing, receiver operating characteristic curve analysis to evaluate predictive performance, Kaplan–Meier survival analysis, and Cox proportional hazards regression to identify independent predictors of mortality. Sample size was based on available eligible cases during the study period. Results The neutrophil–monocyte to lymphocyte ratio demonstrated moderate discrimination for predicting one-year mortality, with significantly lower survival observed in patients with higher values. Each unit increase in the ratio was independently associated with higher mortality risk after adjustment for clinical and physiological variables. Higher values were also associated with lower body mass index, poorer lung function, pulmonary hypertension, right heart dysfunction, respiratory failure, and increased exacerbation frequency. The NMLR ratio showed slightly higher AUC values than the neutrophil-to-lymphocyte ratio. Conclusions An elevated neutrophil–monocyte to lymphocyte ratio is independently associated with increased one-year mortality and markers of disease severity in hospitalized chronic obstructive pulmonary disease patients. As an inexpensive and readily available biomarker, it may aid clinical risk stratification, although prospective multicenter validation is required before routine implementation.