Neutrophil-to-lymphocyte ratio in aging: Trends and clinical implications

The neutrophil-to-lymphocyte ratio (NLR) has emerged as a widely accessible and cost-effective marker of systemic inflammation, derived from routine peripheral blood counts. It has demonstrated clinical relevance across a broad spectrum of conditions, including infections, cardiovascular disease, malignancies, trauma, postoperative complications, and cancer. Aging is associated with a gradual rise in NLR, driven by increasing neutrophil counts and declining lymphocyte numbers, reflecting underlying immunosenescence and systemic inflammation. Elevated NLR in older adults has been linked to greater morbidity and mortality, with higher levels correlating with increased risk, disease severity, and poorer clinical outcomes in age-related conditions. Interestingly, centenarians exhibit a slower age-related increase in NLR compared with non-centenarians, suggesting a more resilient immune system. This narrative review synthesizes current evidence on the trajectory of NLR across the human lifespan and its clinical relevance in the diagnosis, prognosis, and management of selected age-related diseases. Additionally, it explores emerging strategies to mitigate age-related NLR increases, including regular physical activity, targeted dietary interventions, and pharmacological approaches. A deeper understanding of NLR dynamics may inform preventive and therapeutic strategies to enhance health outcomes in aging populations.