Evaluation of the relationship between insomnia and inflammatory markers in geriatric individuals: a cross-sectional study

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This study aimed to investigate the association between insomnia severity and systemic inflammatory indices, specifically neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and systemic immune-inflammation index (SII), in geriatric individuals aged 80 years and older, a subgroup for whom evidence on this relationship remains scarce. This cross-sectional study included 384 patients aged ≥ 80 years attending a geriatric outpatient clinic. Insomnia severity was assessed using the Insomnia Severity Index (ISI). Inflammatory markers, namely the NLR, PLR, and SII were derived from routine hematological parameters and analyzed via correlation analyses and multivariable linear regression. Insomnia was identified in 38.5% of participants. ISI scores showed significant positive correlations with NLR, PLR, SII, chronic disease burden, and medication count (all p < 0.001). Inflammatory marker levels were significantly elevated in those with insomnia ( p < 0.001). After full covariate adjustment, SII (β = 0.07, p < 0.001) and NLR (β = 0.666, p = 0.004) remained independent predictors of insomnia severity, whereas PLR lost significance. Insomnia is highly prevalent in the oldest-old and independently associated with systemic inflammatory burden. SII and NLR, as accessible and non-invasive parameters, may serve as pragmatic biomarkers for stratifying insomnia severity in geriatric practice. Longitudinal studies are warranted to establish causality and evaluate anti-inflammatory interventions.