The relationship among Aβ‐42 and p‐Tau biomarkers, functionality and cognition in patients without cognitive impairment and patients with Alzheimer’s dementia

Abstract

Background Comparison between functionality and cognition in elderly patients with Alzheimer’s dementia (AD) and without cognitive impairment with positive and negative Aβ‐42 and p‐Tau biomarkers evaluated using the Luminex technique. Method Patients with Alzheimer’s dementia and normal cognition (control) were recruited. They were divided in two groups according to their clinical diagnosis: AD group (n=30) and control group (CTRL) (n=10). The AD group was then divided in patients with positive (n=21) and negative (n=9) Aβ‐42 and p‐Tau biomarkers. The participants were submitted to sociodemographic. The general cognition was evaluated through the following instruments: the Mini‐Mental State Examination (MMSE), semantic verbal fluency (SVF), animal fluency, short term memory, and recognition of CERAD battery, and functionality was evaluated by the Pfeffer scale. Samples from the cerebrospinal fluid (CSF) of patients were collected, processed, and stored at ‐80°C until use. The Luminex technique was then used for the Aβ‐42, t‐Tau, p‐Tau, t‐Tau/Aβ‐42 ratio, and p‐Tau/Aβ‐42 ratio biomarker analysis. Obtained data was processed and analyzed through the software SPSS 22.0. Result Comparison between control patients and patients with AD, as defined by clinical diagnosis, did not show significant differences regarding to Aβ‐42 expression in CSF (U=91,000; p=0,067), (AD=1119,0360, SD=708,98952 vs CTRL=775,2623 SD=341,67835). However, there was a significant difference between groups concerning t‐Tau protein, (U=198,500; p=0,028), p‐Tau (U=250,00, p=0,001) and p‐Tau/Aβ‐42 ratio (U=238,00; p=0,005). In terms of cognitive variables, all showed significant differences between groups: MMSE (U=46,500, p=0,001), SVF (U=39,000; p<0,001), short term memory (U=27,000, p<0,001), recognition (U=72,500,p=0,014), as well as functionality (U=258,500, p<0,001). There was no difference regarding the age (U= 201,500; p=0,109) and formal education (U=201,500, p=0,109). As for the AD groups with positive and negative biomarkers, there was no significant difference in cognitive variables, age, formal education, and functionality. Conclusion AD group with negative biomarkers non differ in terms of cognition. Comparing the control and AD groups, there were differences in functionality, cognition, and biomarkers. However, comparing AD groups in terms of biomarkers, there was no difference in functionality performance, short‐term memory, fluency and general cognition. Therefore, the biomarkers do not indicate significant cognitive differences in the group of patients with dementia.