Eyes-open and eyes-closed EEG of older adults with subjective cognitive impairment versus healthy controls: a frequency principal components analysis study

Subjective Cognitive Impairment (SCI) is a self-perceived worsening of cognitive decline, carrying an increased risk of developing Mild Cognitive Impairment (MCI) and Alzheimer's Disease (AD). Due to the self-report nature of SCI, an understanding of the biological mechanisms that contribute to an increased dementia risk is needed. This study aims to assess the differences in resting state electroencephalography (EEG) (eyes-open, eyes-closed; EO, EC) between older adults with SCI and healthy controls (HCs) utilising frequency principal components analysis (fPCA), a novel data driven approach. Participants (n = 14 per group: SCI, HCs) were matched on age, sex, years of education, mood, cognition, and pre-morbid function. Continuous resting EEG was recorded during 2-minute conditions (EO, EC) and were submitted to 4 separate fPCAs (each condition, group). Corresponding components were assessed between groups and conditions, correlated with demographics, mood, and cognition variables; multivariate logistic regression was also carried out. Component amplitudes were larger in HCs for delta-theta and alpha-beta, while theta-alpha was larger for SCI. DASS anxiety scores contributed to higher amplitudes for HCs in EO delta-theta and alpha-beta, while male sex and depressive symptoms contributed to higher amplitudes for the SCI group in EO and EC theta-alpha. Findings demonstrate a distinct divergent signature of neurological activity in older people with SCI, despite normal objective cognitive function. This is the first fPCA study to investigate neuronal differences between HCs and older adults with SCI at rest. Novel confounders and effect modifiers were identified that should be controlled in future studies.