Top Things to Know: Impact of Sleep Disorders and Disturbed Sleep on Brain Health
Published: January 18, 2024
Prepared by Philip Gorelick MD, Division of Stroke and Neurocritical Care, Davee Department of Neurology Northwestern University Feinberg School of Medicine
- There is accumulating evidence to support a link between sleep disorders, disturbed sleep, and compromised brain health including the occurrence of heightened stroke risk, subclinical cerebrovascular disease, and compromised cognitive outcomes stemming from vascular and neurodegenerative mechanisms.
- A wide range of sleep disorders such as sleep-disordered breathing (e.g., obstructive sleep apnea [OSA]) and other sleep-related disturbances (e.g., insomnia, sleep fragmentation, circadian rhythm disorders, and increased sleep duration) may be associated with compromised brain health.
- The structure (i.e., architecture) of sleep varies across the lifespan and reduced sleep quality such as greater fragmentation and light sleep, substantial reductions in the NREM N3 stage of sleep (i.e., deep sleep) and REM sleep, and sleep quantity are more prevalent at older ages and among those with certain co-morbidities (e.g., obesity).
- NREM sleep features including slow oscillations and sleep spindles and REM sleep play complementary and overlapping roles in the process of ‘memory consolidation’ whereby unstable memories are relocated from the hippocampus to the neocortex where they become durable.
- At the cellular and molecular levels, there is experimental evidence to support that memory consolidation occurs through a process called ‘synaptic homeostasis’ during the N3 phase of sleep.
- The brain houses a deep perivascular waste removal system, the glymphatic system, which may be driven by vascular pulsatility and vasomotion, and aided by aquaporin-4 water channels on glial end-feet that facilitate perivascular cerebrospinal fluid exchange for waste removal.
- Glymphatic system activity is dependent on the sleep state and is enhanced during NREM N3 sleep. Disruption of sleep (especially N3 sleep) could result in accumulation of brain waste such as beta amyloid.
- Both short and long sleep duration have been associated with greater risk of stroke. OSA is associated with greater risk of certain forms of cerebral small vessel disease (e.g., white matter hyperintensities, lacunar infarcts) and diminished cerebral blood flow, especially in the temporal regions, which may be reversed by administration of continuous positive airway pressure (CPAP).
- Insomnia may be associated with microstructural changes of white matter tracts connecting subcortical nuclei to the prefrontal cortex, and less NREM N3 stage sleep is associated with higher white matter hyperintensity and lower cortical gray matter volumes.
- There is an increased risk of dementia, mild cognitive impairment, and Alzheimer’s disease with OSA which may be mediated by hypoxemia and beta amyloid and tau accumulation, neuroinflammation, and hippocampal volume loss. Greater NREM N3 stage activity and sleep efficiency may protect against accumulation of beta amyloid, whereas less NREM N3 sleep may be linked to smaller brain volumes.
- The importance of sleep and related disturbances as foundational risks for compromised cardiovascular and brain health is highlighted by the addition of sleep to the original AHA Life’s Simple 7 formula for cardiovascular health, now referred to as Life’s Essential 8.
- Treatment of OSA with CPAP is promising for preservation of brain health as CPAP may improve neurological function, quality of life, depression, language after stroke, and cognition. Currently, however, the quality of evidence is suboptimal, the results mixed, and the duration of follow-up has been relatively limited.
- Underrepresented groups have a high risk for poor sleep quality, quantity, and sleep disorder diagnoses, and there remain substantial health inequities in relation to diagnosis and access to sleep care among these groups. Individuals of underrepresented races and ethnicities are more likely to have sleep-related chronic illness, and disproportionate sleep loss in Black versus White adult’s accounts for some observed disparities in cardiometabolic health. Women, Black and Hispanic/Latino adults are often underdiagnosed and are untreated for OSC and other sleep disorders. Multilevel social determinants of health may play a role in equitable treatment and treatment adherence.
Citation
Gottesman RF, Lutsey PL, Benveniste H, Brown DL, Full KM, Lee J-M, Osorio RS, Pase MP, Redeker NS, Redline S, Spira AP; on behalf of the American Heart Association Stroke Council; Council on Cardiovascular and Stroke Nursing; and Council on Hypertension. Impact of sleep disorders and disturbed sleep on brain health: a scientific statement from the American Heart Association. Stroke. Published online January 18, 2024. doi: 10.1161/STR.0000000000000453