Cerebral amyloid angiopathy interacts with parenchymal beta‐amyloid to promote tau and cognitive decline

Abstract

AbstractBackgroundPrior work has shown that cerebrovascular disease contributes to Alzheimer’s disease (AD) pathophysiology and progression toward AD dementia. Cerebral amyloid angiopathy (CAA) is a form of cerebrovascular pathology that results from the buildup of β‐amyloid (Aβ) in the vessel walls. CAA commonly co‐occurs with AD pathology and increases the risk of AD dementia. Here, we examined whether CAA influences tau deposition and cognitive decline, independently or synergistically with parenchymal Aβ burden. Secondarily, we examined whether tau burden mediates the association between CAA and cognitive decline.MethodWe included data from autopsied subjects recruited from one of three longitudinal clinical‐pathological cohort studies at Rush University. Participants completed annual cognitive evaluations and underwent brain autopsy. CAA pathology was rated as none, mild, moderate, or severe. We used linear regression and linear mixed models to test independent versus interactive effects of CAA and neuritic plaques on tau burden and cognitive decline. We used causal mediation models to examine whether tau mediates the association between CAA and cognitive decline at low and high neuritic plaque burden.ResultWe included 1722 autopsied subjects (mean age at baseline = 80.2+7.1; mean age at death = 8.9+6.7; 68% women). CAA interacted with neuritic plaques to promote tau burden and cognitive decline, such that those with more severe CAA and higher neuritic plaque burden exhibited greater tau and faster cognitive decline (Figures 1 and 2). Tau mediated the effect of CAA on cognitive decline among participants with high neuritic plaque burden. Specifically, increased tau pathology due to the presence of severe CAA led to a 5‐year decline in cognition that was 0.10 (95% CI: 0.03 ‐ 0.19) SD units greater than those with no CAA. A direct effect of CAA on cognitive decline (i.e., an effect not mediated by tau) was not significant in the low or high neuritic plaque groups (Figure 3).ConclusionThese results highlight the dynamic interplay between cerebrovascular and AD pathways in the progression of AD. The present findings have implications for AD clinical trials and therapeutic development, and further support the idea that improving and/or preserving the brain’s vasculature might be an effective target for AD prevention