Association of inflammatory proteins with cognitive aging, brain MRI markers, and incident dementia

Abstract Background Inflammatory cytokines and chemokines related to the innate and adaptive immune system have been linked to neuroinflammation in Alzheimer’s Disease (AD) dementia. We hypothesized that individual blood‐based inflammatory biomarkers would associate with cognitive function, brain magnetic resonance imaging (MRI) volumes, and risk for dementia in Framingham Heart Study (FHS) participants. Method Protein biomarkers related to immune cells or associated with inflammatory responses including CD14, CD163, CD5L, CD56, CD40L, CXCL16, SDF1, DPP4, SGP130, sRAGE, and MPO were measured at FHS Offspring exam 7. We identified FHS Offspring participants who underwent neuropsychological (NP) testing (n = 2394) or brain MRI (n = 2135) within five years of the examination; and who were followed up 10 years after age 60 for incident all‐cause dementia (n = 1650). We used linear mixed effect models accounting for family relationships to investigate the associations between the protein biomarkers and NP test performance and brain MRI volumes and Cox proportional hazards models to examine the association with incident dementia. A false discovery rate (FDR) within each outcome set was computed to adjust for multiple testing and FDR ≤ 0.1 indicated significance. Result Participants from the NP and MRI samples were on average 61 years old and 54% female. Participants from the incident dementia sample (mean age 68 years) included 126 incident dementia cases within 10 years. In addition to CD14 which has an established association, we observed significant associations between higher CD40L and MPO with poorer NP performance from the executive function domain. Higher CD5L levels were significantly associated with smaller total brain volumes (TCBV), whereas higher sRAGE was associated with larger TCBV. Associations persisted after further adjusting for APOE ϵ4 carrier status and cardiovascular risk factors. None of the protein biomarkers included were significantly associated with risk of incident dementia, with trend towards an association for CD5L. Conclusion Since the proinflammatory factors CD5L, CD40L, sRAGE and MPO are associated with immune cells and are involved in vascular pathology, our study suggests the immune‐vascular axis is associated with cognitive and brain aging. If confirmed in other samples, our findings may provide informative biomarkers of abnormal brain aging.