Relationship between insomnia and cognitive function in elderly Chinese cerebral small vessel disease patients: mediating effect of neutrophil-to-lymphocyte ratio.

BACKGROUND: This exploratory study investigated the relationship between insomnia, neutrophil-to-lymphocyte ratio (NLR), and cognitive function in elderly Chinese cerebral small vessel disease (CSVD) patients by integrating subjective and objective sleep assessments, and to analyze the mediating effect of NLR. METHODS: A total of 86 CSVD patients aged ≥ 60 years were enrolled. Sleep was evaluated by polysomnography (PSG) and Pittsburgh Sleep Quality Index (PSQI). Cognitive function was evaluated by Montreal Cognitive Assessment (MoCA). Partial correlation analysis was used to investigate correlations between variables. Regression analysis and the bootstrap method were performed to investigate the mediating effect of NLR between sleep parameters and cognitive function. All models were adjusted for age, gender, years of education, and total CSVD burden. RESULTS: Of the 86 patients, 50 (58.1%) had insomnia and 56 (65.1%) had CSVD-related cognitive impairment (CSVD-CI). Partial correlation analysis revealed that PSQI scores, wake after sleep onset (WASO), and arousal index (ArI) were positively correlated with NLR and negatively correlated with MoCA scores, whereas N3 proportion and sleep efficiency (SE) showed the opposite correlations; NLR was negatively correlated with MoCA scores (P < 0.05 for all). Mediation analysis further revealed that NLR partially mediated associations between the five sleep parameters (PSQI scores, N3, SE, WASO, ArI) and MoCA scores. All indirect effects were statistically significant, as the 95% bootstrap CIs did not include zero. The mediation proportions ranging from 27.50% to 33.72%. CONCLUSION: Insomnia is associated with cognitive impairment in elderly Chinese CSVD patients, a relationship that is partially mediated by elevated NLR.