Relationship between cortical thickness and EEG alterations during sleep in the Alzheimer’s Disease

Recent evidence showed that EEG activity alterations that occur during sleep are associatedwith structural, age-related, changes in healthy aging brains, and predict age-related decline inmemory performance. Alzheimer’s disease (AD) patients show specific EEG alterations during sleepassociated with cognitive decline, including reduced sleep spindles during NREM sleep and EEGslowing during REM sleep. We investigated the relationship between these EEG sleep alterations andbrain structure changes in a study of 23 AD patients who underwent polysomnographic recordingof their undisturbed sleep and 1.5T MRI scans. Cortical thickness measures were correlated withEEG power in the sigma band during NREM sleep and with delta- and beta-power during REMsleep. Thinning in the right precuneus correlated with all the EEG indexes considered in this study.Frontal–central NREM sigma power showed an inverse correlation with thinning of the left entorhinalcortex. Increased delta activity at the frontopolar and temporal regions was significantly associatedwith atrophy in some temporal, parietal, and frontal cortices, and with mean thickness of the righthemisphere. Our findings revealed an association between sleep EEG alterations and the changes toAD patients’ brain structures. Findings also highlight possible compensatory processes involving thesources of frontal–central sleep spindles.