Exploring the Link Between Sleep and Brain Clearance

Inclusion Criteria: * Participation in previous longitudinal cohort studies at the study site * Ability to provide written and verbal informed consent * Fluency in the German language * Stable home situation that allows for reliable application of the intervention for the duration of the study * Ability to apply the intervention for the duration of the study, either alone or with support from a co-habitant * For women: Hormonal contraception, if menstrual cycle is still present or has been present within a year * Good general health status, normal cognitive function Exclusion Criteria: * Failure or inability to give informed consent * Inability to follow the procedures of the investigation * For women: pregnancy or breastfeeding * Presence of sleep disorders (e.g. sleep apnoea, narcolepsy, restless leg syndrome, insomnia, rapid eye movement (REM) sleep disorder) * Shift-work or a home situation that requires several awakenings during the night (e.g. newborn) * History of serious illness likely to interfere with study outcomes * Presence or history of a diagnosed neuropsychiatric illness * Current diagnosis of uncontrolled or poorly controlled diabetes * Current cancer of the brain or unstable cancer undergoing treatment * Evidence of serious atherosclerotic cardiovascular disease