Preserved wake-dependent cortical excitability dynamics predict cognitive fitness beyond age-related brain alterations
Age-related cognitive decline is rooted in alterations in brain integrity as well as in sleep-wake regulation. Here, we investigated whether preserved sleep-wake regulation of cortical function during wakefulness could represent a positive factor for cognitive fitness in aging, independently of early age-related alterations in brain structure associated with Alzheimer's disease neuropathology. We quantified slow waves generation during sleep and cortical excitability dynamics during prolonged
... during prolonged wakefulness as sensitive markers of age-related alteration in sleep-wake regulation in 60 healthy late middle-aged individuals (50-69y; 42 women). We evaluated brain integrity with amyloid-beta-PET and tau-PET, and with MRI. Participants' cognition was extensively assessed. We first confirm that sleep slow waves generation is associated with amyloid-beta burden. Although cortical excitability dynamics during wakefulness is related to sleep slow waves, it is not associated with amyloid-beta nor with tau burden. We further show that individuals with preserved cortical excitability dynamics showed better cognitive performance, particularly in the executive domain, which is crucial for successful cognitive aging. Critically, this association remained significant after accounting for brain integrity measures. Preserved dynamics of basic brain function during wakefulness could be essential to cognitive fitness in aging, independently from age-related brain structural deteriorations that can ultimately lead to dementia.