[Dementia and Sleep: A Bidirectional Relationship]

Sleep-waking is regulated by numerous sleep- and wake-promoting nuclei in the brain and biological clocks (suprachiasmatic nucleus). In dementia, organic damage occurs in the brainstem, hypothalamus, and thalamus, where these nuclei and their neural projections are concentrated, resulting in severe insomnia, hypersomnia, and irregular sleep-wake patterns. Numerous cohort studies have strongly suggested that sleep disturbances, such as impaired sleep quality and hypersomnia, may serve as early indicators or risk factors for the onset of dementia. Until recently, the neuropathological mechanisms underlying the association between sleep disturbance and the risk of dementia remained unclear. However, recent advances in research on the glymphatic system and its association with amyloid-beta peptide clearance have begun to elucidate this missing link.