Sleep Loss and Alzheimer’s Disease: Mechanisms, Risk Factors, and Cognitive Consequences—A Narrative Review

Sleep loss is increasingly recognized as a potentially modifiable factor in cognitive aging and Alzheimer’s disease (AD). Evidence supports a bidirectional relationship in which sleep disruption may both reflect early AD-related neurodegenerative changes and contribute to disease progression. This narrative review thematically synthesizes peer-reviewed evidence on the biological mechanisms, sleep-related risk factors, and cognitive consequences linking sleep and AD. Particular attention is given to glymphatic dysfunction, amyloid-β and tau pathology, circadian dysregulation, neuroinflammation, oxidative stress, impaired proteostasis, and synaptic dysfunction. The review also considers clinically relevant sleep phenotypes, including insomnia, obstructive sleep apnea, excessive daytime sleepiness, circadian rhythm disturbance, and reduced slow-wave sleep, as well as their potential effects on memory, attention, executive function, and learning. Although current evidence does not establish that sleep interventions alone can prevent AD, sleep health should be regarded as an important component of brain health, early risk assessment, and dementia risk reduction.