Amyloid-β₄₂ is associated with cognitive impairment in healthy elderly and subjective cognitive impairment.

The aim of this study was to predict cognitive performance on the basis of the cerebrospinal fluid (CSF) biomarkers total tau (T-tau) and amyloid-β₄₂ (Aβ₄₂) in controls and patients at various impairment levels. Previous studies have found an association of CSF T-tau levels with cognitive symptoms, but it has been difficult to relate Aβ to cognition, and it has thus been hypothesized that Aβ reaches a plateau level prior to cognitive symptoms. A comprehensive battery of neuropsychological tests was subjected to factor analysis to yield aggregated cognitive domains. Linear regression models were performed for the total sample of the Gothenburg MCI study (n = 435) and for each level of impairment. Aβ₄₂ and T-tau accounted for a significant proportion of performance in all cognitive domains in the total sample. In controls (n = 60) and patients with subjective cognitive impairment (n = 105), Aβ₄₂ predicted a significant proportion of semantic and working memory performance. For patients with mild cognitive impairment (n = 170), T-tau had the most pronounced impact across cognitive domains, and more specifically on episodic memory, visuospatial, and speed/executive performance. For patients with dementia (n = 100), the most pronounced impacts of Aβ₄₂ were found in episodic memory and visuospatial functioning, while T-tau was substantially associated with episodic memory. Our results suggest that cognition is related to CSF biomarkers regardless of impairment level. Aβ₄₂ is associated with cognitive functions from a potentially early to a later disease phase, and T-tau is more indicative of performance in a later disease phase.