The impact of APOE status on relationship of biomarkers of vascular risk and systemic inflammation to neuropsychiatric symptoms in Alzheimer's disease

Research on the link between APOEε4 and neuropsychiatric symptoms (NPS) in Alzheimer's disease (AD) has been inconsistent. Previous work has shown a relationship between serum biomarkers of vascular risk and inflammation and NPS in AD. The current study investigated the impact of APOEε4 status on the relationship between biomarkers of cardiovascular risk, systemic inflammation, and NPS. The sample was drawn from the TARCC Longitudinal Research Cohort; the final sample of 190 consisted of 124 females and 66 males meeting the diagnostic criteria for mild to moderate AD. 115 individuals were APOEε4 carriers and 75 were non-carriers. Serum-based clinical biomarkers of vascular risk and biomarkers of inflammation related to AD were analyzed. NPS data was gathered from caretakers/family members using the Neuropsychiatric Inventory. The significant biomarkers differed for carriers and non-carriers with IL15 being a negative biomarker of total NPS accounting for 12% of the variance for carriers and IL18 and TNFα negative predictors for non-carriers (18% of variance). Patterns related to specific symptoms were similar. Stratification by gender revealed significant biomarkers of total NPS for female carriers were negative IL15 and IL1ra (18% of variance) and for female non-carriers were negative IL18 and positive homocysteine. Total cholesterol was a positive biomarker of total NPS for both male carriers (36% of variance) and non-carriers (negative TNFα and total cholesterol, 32% of variance). These findings suggest that dysregulation of inflammatory activity is related to NPS, that cholesterol is a significant factor in the occurrence of NPS, and that gender and APOE status need to be considered.