Purpose of review Trouble falling or staying asleep, poor sleep quality, and short or long sleep duration are gaining attention as potential risk factors for cognitive decline and dementia, including Alzheimer's disease. Sleep-disordered breathing has also been linked to these outcomes. Here, we review recent observational and experimental studies investigating the effect of poor sleep on cognitive outcomes and Alzheimer's disease, and discuss possible mechanisms. Recent findings Observational studies with self-report and objective sleep measures (e. g. wrist actigraphy, polysomnography) support links between disturbed sleep and cognitive decline. Several recently published studies demonstrate associations between sleep variables and measures of Alzheimer's disease pathology, including cerebrospinal fluid measures of A beta and PET measures of A beta deposition. In addition, experimental studies suggest that sleep loss alters cerebrospinal fluid A beta dynamics, decrements in slow-wave sleep may decrease the clearance of A beta from the brain, and hypoxemia characteristic of sleep-disordered breathing increases A beta production. Summary Findings indicate that poor sleep is a risk factor for cognitive decline and Alzheimer's disease. Although mechanisms underlying these associations are not yet clear, healthy sleep appears to play an important role in maintaining brain health with age, and may play a key role in Alzheimer's disease prevention.