Amyloid burden correlates with cognitive decline in Alzheimer's disease presenting with aphasia

Background and purpose: A subset of patients with Alzheimer's disease (AD) present with early and prominent language deficits. It is unclear whether the burden of underlying β-amyloid pathology is associated with language or general cognitive impairment in these subjects. Methods: The relationship between cortical β-amyloid burden on [¹¹C]Pittsburgh compound B (PiB) positron emission tomography (PET) and performance on the Montreal Cognitive Assessment (MoCA), the Wechsler Memory Scale - Third Edition (WMS-III), the Boston Naming Test (BNT) and the Western Aphasia Battery (WAB) was assessed using regression and correlation analyses in subjects presenting with aphasia who showed β-amyloid deposition on PiB PET. Results: The global PiB ratio was inversely correlated with MoCA (P = 0.02) and the WMS-III Visual Reproduction (VR) subtest (VR I, P = 0.02; VR II, P = 0.04). However, the correlations between PiB ratio, BNT (P = 0.13), WAB aphasia quotient (P = 0.11) and WAB repetition scores (P = 0.34) were not significant. Conclusion: This study demonstrates that an increased cortical β-amyloid burden is associated with cognitive impairment, but not language deficits, in AD subjects presenting with aphasia. The results suggest that β-amyloid deposition could be partly contributing to impaired cognition in such patients whilst language dysfunction may be more influenced by other pathological mechanisms, perhaps downstream pathways of β-amyloid deposition.