Association between Cerebrospinal Fluid Biomarkers for Alzheimer's Disease, APOE Genotypes and Auditory Verbal Learning Task in Subjective Cognitive Decline, Mild Cognitive Impairment, and Alzheimer's Disease

In the course of Alzheimer's disease (AD), early pathological changes in the brain start decades before any clinical manifestation. The concentration levels of AD cerebrospinal fluid (CSF) biomarkers, such as amyloid-beta(1-42) (A beta(1-42)), total tau (T-tau), and phosphorylated tau (P-tau), may reflect a cerebral pathology facilitating an early diagnosis of the disease and predicting a cognitive deterioration. The aim of this study was to estimate the prevalence of AD CSF biomarkers in those individuals with a subjective cognitive decline (SCD), a mild cognitive impairment (MCI), and Alzheimer's dementia (AD-D), together with the relationships between the biomarkers, an APOE epsilon(4) presence, and a verbal episodic memory performance. We included 252 patients from the memory clinic with a diagnosis of SCD (n = 85), MCI (n = 87), and AD-D (n = 80). A verbal episodic memory performance level was assessed and was based on a delayed recall trial from the 10-word list of an auditory verbal learning task (AVLT). We found that the patients with more severe cognitive impairments had significantly lower levels of A beta(1-42) and higher levels of T-tau and P-tau. This pattern was also typical for the APOE epsilon(4) carriers, who had lower levels of A beta(1-42) than the noncarriers in the AD-D and MCI groups. The levels of T-tau and P-tau were significantly higher in the APOE epsilon(4) carriers than in the noncarriers, but only in the MCI patients. The AVLT performance in the whole study samples was predicted by age, A beta(1-42), and the T-tau CSF biomarkers, but not by the APOE genotyping.