Objective: Smoking has been proven to increase systemic inflammation in previous studies using different biomarkers. The eosinophil-to-lymphocyte ratio (ELR), neutrophil-to-lymphocyte ratio (NLR), and lymphocyte-to-monocyte ratio (LMR) are new indicators of systemic inflammation that are used as predictors of systemic inflammation, morbidity, and mortality associated with many diseases. We investigated the effects of smoking on these inflammatory indicators.
Methods: In total, 616 consecutive smoking healthy subjects and 387 age-matched nonsmoking healthy subjects were enrolled. White blood cell counts (neutrophils, lymphocytes, basophils, eosinophils, and monocytes) were determined by electrical impedance with an automatic blood cell counting device. The ELR, LMR, and NLR were calculated based on these cell counts. Smoking habits of participants were calculated as pack/year.
Results: The NLR and ELR were significantly higher and the LMR was significantly lower in smokers than nonsmokers. The pack-years were positively correlated with the NLR and ELR and negatively correlated with the LMR.
Conclusion: A high NLR and ELR and low LMR are associated with cigarette smoking and may be useful indicators of systemic inflammation activity, even in healthy smokers. Smokers with a high NLR and ELR and low LMR can easily be identified during routine blood analysis and might benefit from preventive treatment.
Keywords: Cigarette smoking; biomarkers; complete blood cell count; eosinophil-to-lymphocyte ratio; lymphocyte-to-monocyte ratio; neutrophil-to-lymphocyte ratio; systemic inflammation.