Neutrophil-to-Lymphocyte Ratio as a Prognostic Biomarker for Long-Term Survival in Older Adults at a Mental Health Care Center: A Historical Cohort Analysis

<b>Background/Objectives</b>: Identifying reliable biomarkers for healthy aging and longevity is a fundamental challenge in aging research and medical sciences. The neutrophil-to-lymphocyte ratio (NLR) is a readily measurable indicator of immune balance that reflects the interplay between innate immune activation and adaptive immune suppression. <b>Methods</b>: This study examined NLR values in 204 physically healthy residents (98 men and 106 women) stratified into four lifespan categories based on death certificates. Page's test and ordinal regression (Cumulative Link Model) were used to assess trends with longevity. <b>Results</b>: In men, a downward trend in NLR values was observed. In women, a significant age-related decline in NLR was identified, with longer-lived individuals showing notably lower NLR values compared to their shorter-lived counterparts. The findings suggest that lower NLR is associated with longer survival, particularly in older women, reflecting superior immune regulation and reduced systemic inflammation. Conversely, elevated NLR may indicate immune dysfunction and heightened inflammatory burden. <b>Conclusions</b>: The results of this study complement existing findings, reinforcing the critical importance of immune balance in supporting healthy aging and longevity. These findings also underscore the potential of NLR as a robust biomarker for evaluating immune function and anticipating resilience to age-related decline, offering a practical tool for assessing immune health in the aging population.