The Relationship Between the Abnormal Electrophysiological Features and the Degeneration in Cognition, Behavior, Daily Functioning, and Global Presentation Manifested by Individuals with Alzheimer's Disease

Abstract

Alzheimer's disease (AD) is an increasingly prevalent neurologic disorder characterized by progressive degeneration in cognition, behavior, and daily functioning. Identification of methods designed to enhance the accuracy and efficiency of early diagnosis would allow for proactive care including timely implementation of treatment modalities. Toward this goal, this secondary analysis was designed to examine the relationship between clinical symptoms (cognitive, behavioral, and daily functioning) and abnormal electrophysiological features in individuals with AD. The sample included 100 community-residing adults, aged 50–89 years, and ranged from normal-functioning elderly to those diagnosed with severe AD. The baseline (BL) and follow-up (FU) diagnostic data were extracted for analysis from two full databases. Neuropsychological data included the Global Deterioration Scale (GDS), the Mini Mental Status Examination (MMSE), the Behavioral Pathology in Alzheimer's disease Rating Scale (BEHAVE-AD), and the Functional Assessment Staging of Alzheimer's disease (FAST). Electrophysiological data included neurometric quantitative electroencephalogram (qEEG) using the 10/20 International System. A moderately strong relationship (|r| = .38–.66, p ≤ .001) existed between abnormal electrophysiological features and clinical symptoms in community-residing adults with AD. A multivariate set of BL abnormal electrophysiological features explained 86% of the variance in a multivariate set of FU clinical symptoms with canonical correlations. A backward deletion multiple regressional model demonstrated that a predictor of multivariate BL abnormal electrophysiological features explained a minimum of 50% of the variance in individual FU clinical symptoms. The earliest preclinical symptoms observed were degeneration in daily functioning skills, absolute/relative delta deficit, and absolute/relative/mean frequency theta excess in frontal regions of normal-functioning elderly. Theta excess in absolute power, relative power, and mean frequency was prominent and diffusely progressed from the frontal regions to the posterior, from mild cognitive impairment (MCI) to severe AD. Behavioral degeneration, as indicated by a mean of 0.5±1.4 at stage FU GDS 2, was manifested before cognitive degeneration. The findings suggest that inclusion of electrophysiological evaluation enhances early, accurate diagnosis of AD. Longitudinal outcome studies of the relationship between abnormal electrophysiological features and clinical symptoms are suggested to inform interventions designed to delay and prevent the progression of AD.