Abstract
The neutrophil-to-lymphocyte ratio (NLR) has emerged as a readily accessible, cost-effective biomarker reflecting systemic inflammation. Chronic low-grade inflammation plays a pivotal role in the pathogenesis and progression of metabolic and cardiovascular disorders including chronic kidney disease (CKD), hypertension, diabetes mellitus, and cardiovascular disease (CVD). This review critically evaluates the current evidence on NLR as a prognostic marker across these interconnected conditions. A comprehensive literature search was conducted focusing on clinical and epidemiological studies investigating the association between NLR and CKD, hypertension, diabetes, and cardiovascular outcomes. Mechanistic insights into inflammation-driven pathophysiology and the predictive utility of NLR in disease progression and adverse events were synthesized. Elevated NLR is consistently associated with increased risk and severity of CKD, correlating with glomerular filtration decline, proteinuria, and mortality. In hypertension, higher NLR levels are linked to non-dipper blood pressure patterns, arterial stiffness, and increased cardiovascular risk. Among diabetic patients, NLR correlates with poor glycemic control and vascular complications. In cardiovascular disease, elevated NLR predicts major adverse cardiovascular events (MACE) and all-cause mortality, reflecting underlying immune dysregulation and endothelial dysfunction. Despite promising findings, direct comparisons with established inflammatory biomarkers remain limited, and heterogeneity exists across populations. NLR represents a simple yet powerful inflammatory biomarker with significant prognostic value in CKD, hypertension, diabetes, and cardiovascular disease. Its integration into clinical risk stratification models could enhance personalized medicine approaches. Future research should focus on longitudinal studies, validation in diverse cohorts, and comparative analyses with other inflammatory markers to fully delineate NLR's clinical utility.