Lucey BP, et al. - In participants who partook in longitudinal studies of aging, cognitive performance, brain imaging, and cerebrospinal fluid (CSF) Alzheimer’s disease (AD) biomarkers were assessed. Investigators also used a single-channel electroencephalography (EEG) device worn on the forehead to monitor their sleep. They found that non–rapid eye movement (NREM) slow wave activity (SWA) had an inverse association with AD pathology, especially tauopathy, and that this relationship was most evident at the lowest NREM SWA frequencies after adjusting for multiple covariates such as age and sex. Participants were mostly cognitively normal with the rest having only very mild impairment, suggesting that decreased NREM SWA, especially at the lowest 1- to 2-Hz frequencies, could be linked with tau pathology prior to or at the earliest stages of cognitive decline.