Associations of Blood Absolute Neutrophil Count and Cytokines With Cognitive Function in Dementia-Free Participants: A Population-Based Cohort Study

Background The relationships of neutrophils and cytokines with cognitive dysfunction are poorly defined. We aimed to investigate the association of peripheral blood absolute neutrophil count (ANC) with cognitive function in older adults and to further explore the mediating role of serum cytokines in this association.Methods This population-based cohort study included 1 666 dementia-free participants (age >= 60 years) derived from baseline examinations (March-September 2018) of the Multimodal Intervention to Delay Dementia and Disability in Rural China (MIND-China); of these, 1 087 participants completed follow-up examinations in October-December 2019. We used a neuropsychological test battery to assess episodic memory, verbal fluency, attention, and executive function at the baseline and follow-up examinations. We used Mindray BC-6800 automated hematology analyzer to measure ANC and Meso Scale Discovery to measure serum interleukin-6 (IL-6) and eotaxin-3.Results The linear regression analysis of cross-sectional data at baseline (n = 1 666) suggested that increased ANC was significantly associated with a lower episodic memory z score (beta coefficient: -0.149, 95% CI: -0.274 to -0.023) and lower long-delayed free recall z score (-0.216, -0.361 to -0.070). Serum IL-6 and eotaxin-3 could mediate 16.16% to 20.21% and 7.55% to 9.35%, respectively, of these associations. The analysis of longitudinal data (n = 1 087) showed a J-shaped relationship of ANC with decline in episodic memory z score (p for nonlinear = .049), and a U-shaped relationship between ANC and decline in long-delayed free recall z score (p for nonlinear = .043).Conclusions Increased neutrophils are associated with poor cognitive performance and accelerated decline in episodic memory, and the cross-sectional association is partly mediated by serum cytokines.