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Accumulating evidence supports a link between sleep disorders, disturbed sleep, and adverse brain health, ranging from stroke to subclinical cerebrovascular disease to cognitive outcomes, including the development of Alzheimer disease and Alzheimer disease-related dementias. Sleep disorders such as sleep-disordered breathing (eg, obstructive sleep apnea), and other sleep disturbances, as well, some of which are also considered sleep disorders (eg, insomnia, sleep fragmentation, circadian rhythm disorders, and extreme sleep duration), have been associated with adverse brain health. Understanding the causal role of sleep disorders and disturbances in the development of adverse brain health is complicated by the common development of sleep disorders among individuals with neurodegenerative disease. In addition to the role of sleep disorders in stroke and cerebrovascular injury, mechanistic hypotheses linking sleep with brain health and biomarker data (blood-based, cerebrospinal fluid-based, and imaging) suggest direct links to Alzheimer disease-specific pathology. These potential mechanisms and the increasing understanding of the "glymphatic system," and the recognition of the importance of sleep in poststroke recovery, as well, support a biological basis for the indirect (through the worsening of vascular disease) and direct (through specific effects on neuropathology) connections between sleep disorders and brain health. Given promising evidence for the benefits of treatment and prevention, sleep disorders and disturbances represent potential targets for early treatment that may improve brain health more broadly. In this scientific statement, we discuss the evidence supporting an association between sleep disorders and disturbances and poor brain health ranging from stroke to dementia and opportunities for prevention and early treatment.

Objective: Studies of modifiable dementia risk factors (MDRFs) generally consider MDRFs individually, despite strong evidence that they co-occur in adult populations. In a large sample of middle-aged adults, this study aimed to determine the frequency and co-occurrence of MDRFs, spanning five domains (mood symptomatology, risky lifestyle behaviors, cardiovascular conditions, cognitive/social engagement, sleep disorders/symptomatology). The relationship between number of domains in which MDRFs were reported with cognitive performance and subjective cognitive concerns was then determined., Method: Middle-aged adults ( n = 1,610) enrolled in the Healthy Brain Project and completed self-report surveys about their health and lifestyle. Participants also completed the Cogstate Brief Battery and the Cognitive Function Instrument, a measure of subjective ratings of cognition. Participants were classified according to number of domains (mood symptomatology, risky lifestyle behaviors, cardiovascular conditions, cognitive/social engagement, sleep disorders/symptomatology) in which they reported at least one MDRF (0-5). Age, sex, education, and ethnicity were adjusted for in analyses., Results: Most individuals (66.5%) reported MDRFs in two or more domains. Compared with individuals displaying no MDRFs, individuals with MDRFs in 3-5 domains showed worse learning/working memory performance and greater subjective cognitive concerns, with the magnitude of these differences moderate-to-large ( d = 0.30-0.93). Individuals displaying MDRFs in five domains also showed worse attention/psychomotor function ( d = 0.58) compared to those displaying no MDRFs., Conclusions: These findings may suggest that multidomain MDRFs are highly frequent in middle-aged adults and are related to poorer cognition. This supports that modifiable dementia risk is multidimensional and raises the possibility that multidomain behavioral intervention trials in middle-aged adults may be useful to delay or prevent cognitive impairment or decline. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Study Objectives: To examine if sleep symptomatology was associated with subjective cognitive concerns or objective cognitive performance in a dementia-free community-based sample., Methods: A total of 1,421 middle-aged participants (mean ± standard deviation = 57 ± 7; 77% female) from the Healthy Brain Project completed the Pittsburgh Sleep Quality Index, Insomnia Severity Index, and Epworth Sleepiness Scale to measure sleep quality, insomnia symptom severity, and daytime sleepiness, respectively. Participants were classified as having no sleep symptomatology (normal scores on each sleep measure), moderate sleep symptomatology (abnormal scores on one sleep measure), or high sleep symptomatology (abnormal scores on at least two sleep measures), using established cutoff values. Analysis of covariance was used to compare objective cognitive function (Cogstate Brief Battery) and subjective cognitive concerns (Modified Cognitive Function Instrument) across groups., Results: Following adjustments for age, sex, education, mood, and vascular risk factors, persons classified as having high sleep symptomatology, versus none, displayed more subjective cognitive concerns (d = 0.24) but no differences in objective cognitive performance (d = 0.00-0.18). Subjective cognitive concerns modified the association between sleep symptomatology and psychomotor function. The strength of the relationship between high sleep symptomatology (versus none) and psychomotor function was significantly greater in persons with high as compared with low cognitive concerns (β ± SE = -0.37 ± 0.16; p = 0.02)., Conclusions: More severe sleep symptomatology was associated with greater subjective cognitive concerns. Persons reporting high levels of sleep symptomatology may be more likely to display poorer objective cognitive function in the presence of subjective cognitive concerns., (© Sleep Research Society 2021. Published by Oxford University Press on behalf of the Sleep Research Society. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Objective: To test the hypothesis that reduced slow-wave sleep, or N3 sleep, which is thought to underlie the restorative functions of sleep, is associated with MRI markers of brain aging, we evaluated this relationship in the community-based Framingham Heart Study Offspring cohort using polysomnography and brain MRI., Methods: We studied 492 participants (age 58.8 ± 8.8 years, 49.4% male) free of neurological diseases who completed a brain MRI scan and in-home overnight polysomnography to assess slow-wave sleep (absolute duration and percentage of total sleep). Volumes of total brain, total cortical, frontal cortical, subcortical gray matter, hippocampus, and white matter hyperintensities were investigated as a percentage of intracranial volume, and the presence of covert brain infarcts was evaluated. Linear and logistic regression models were adjusted for age, age squared, sex, time interval between polysomnography and MRI (3.3 ± 1.0 years), APOE ε4 carrier status, stroke risk factors, sleeping pill use, body mass index, and depression., Results: Less slow-wave sleep was associated with lower cortical brain volume (absolute duration, β [standard error] = 0.20 [0.08], p = 0.015; percentage, 0.16 [0.08], p = 0.044), lower subcortical brain volume (percentage, 0.03 [0.02], p = 0.034), and higher white matter hyperintensities volume (absolute duration, -0.12 [0.05], p = 0.010; percentage, -0.10 [0.04], p = 0.033). Slow-wave sleep duration was not associated with hippocampal volume or the presence of covert brain infarcts., Conclusion: Loss of slow-wave sleep might facilitate accelerated brain aging, as evidence by its association with MRI markers suggestive of brain atrophy and injury. Alternatively, subtle injuries and accelerated aging might reduce the ability of the brain to produce slow-wave sleep., (© 2020 American Academy of Neurology.)

Study Objectives: To determine whether C-reactive protein (CRP), a marker of systemic inflammation, moderates the association between sleep and incident dementia., Methods: We studied Framingham Heart Study participants who completed at baseline a serum CRP assessment and in-home polysomnography to measure sleep duration, sleep efficiency, sleep latency, wake after sleep onset (WASO), number of awakenings, arousal index, and apnea-hypopnea index. Participants were divided into groups according to their CRP level: low (<1 mg/L), average (1-3 mg/L), and high inflammation (>3 mg/L). Surveillance for outcomes (incident all-cause and Alzheimer's disease [AD] dementia) commenced at baseline and continued up to 22.5 years., Results: In 291 participants (mean age 67.5 ± 4.9 years, 51.6% men) followed for 13.4 ± 5.4 years, we observed 43 cases of all-cause dementia, 33 of which were clinically consistent with AD. Whereas no direct association between CRP or sleep exposures was observed with incident dementia, CRP levels interacted with nighttime wakefulness when predicting both incident all-cause and AD dementia. In the high CRP group, longer WASO (hazard ratio [HR], 2.89; 95% CI, 1.31-6.34) and more nighttime awakenings (HR, 4.55; 95% CI, 1.19-17.38) were associated with higher risk of incident dementia. In the low CRP group, fewer nighttime awakenings were associated with a higher risk of incident dementia (HR, 0.07; 95% CI, 0.01-0.68)., Conclusions: Our findings suggest that inflammation moderates the association between sleep, particularly nighttime wakefulness, and dementia risk. The presence of inflammation may be an important determinant in evaluating how sleep disturbances relate to neurodegeneration., (© Sleep Research Society 2020. Published by Oxford University Press on behalf of the Sleep Research Society. All rights reserved. For permissions, please e-mail journals.permissions@oup.com.)

The burden of dementia is increasing globally. In the absence of curative treatment, preventive strategies to delay or reduce progression of dementia are crucial. This relies on the identification of modifiable risk factors. The effects of dementia on sleep are well recognized; however, there is now growing evidence suggesting a bidirectional relationship between sleep pathologies and dementia. SDB, poor quality sleep and extremes of sleep duration are commonly experienced by both middle-aged and older populations. All have been associated with increased risk of dementia and cognitive decline in a number of observational studies, albeit inconsistently. The mechanisms by which these sleep disorders may contribute to neurodegeneration are manifold, and include impacts of fragmented sleep on the clearance of neurotoxins, and in SDB by the additive effects of intermittent hypoxia on beta-amyloid production, hypoxic cell death, neuroinflammation and damage to cerebral vasculature. Untangling the mechanisms by which sleep pathologies may impact risk of dementia is a challenge. Many insights into the pathophysiology of these relationships have been derived from animal- and population-based studies. Neuroimaging modalities offer important opportunities to further understand the link between sleep pathologies and dementia risk in vivo, especially in the critical preclinical phase of AD. In this review, we canvas updates in dementia pathophysiology, the evidence linking sleep pathologies with dementia and outline the advances in determining this potential pathophysiological link that have eventuated from the application of neuroimaging., (© 2019 Asian Pacific Society of Respirology.)

Purpose of Review: Recent research has provided extensive characterization as to the frequency and nature of sleep disturbances following traumatic brain injury (TBI). This review summarizes the current state of knowledge and proposes future directions for research., Recent Findings: Complaints of sleep disturbance are common following TBI, and objective assessments of sleep largely corroborate these complaints. Sleep is often disturbed in the acute phase postinjury and can persist for decades, with the prevalence of sleep disorders higher in patients with TBI as compared with the general population. The factors causing sleep disturbance appear to involve numerous interrelated primary and secondary factors, including direct damage to vital sleep-regulating regions of the brain, alterations in the circadian system, lowered mood as well as increased anxiety and pain. The complex web of contributing factors implies that combination therapies targeting a number of putative causal mechanisms may yield the greatest success in terms of improving sleep postinjury., Summary: Sleep disturbance is a common consequence of TBI. Research is needed to ascertain the primary drivers of sleep disturbance postinjury to guide the development of targeted interventions. In the absence of a single mechanism, combination therapies may prove most fruitful.

Objective: Sleep disturbance is common in dementia, although it is unclear whether differences in sleep architecture precede dementia onset. We examined the associations between sleep architecture and the prospective risk of incident dementia in the community-based Framingham Heart Study (FHS)., Methods: Our sample comprised a subset of 321 FHS Offspring participants who participated in the Sleep Heart Health Study between 1995 and 1998 and who were aged over 60 years at the time of sleep assessment (mean age 67 ± 5 years, 50% male). Stages of sleep were quantified using home-based polysomnography. Participants were followed for a maximum of 19 years for incident dementia (mean follow-up 12 ± 5 years)., Results: We observed 32 cases of incident dementia; 24 were consistent with Alzheimer disease dementia. After adjustments for age and sex, lower REM sleep percentage and longer REM sleep latency were both associated with a higher risk of incident dementia. Each percentage reduction in REM sleep was associated with approximately a 9% increase in the risk of incident dementia (hazard ratio 0.91; 95% confidence interval 0.86, 0.97). The magnitude of association between REM sleep percentage and dementia was similar following adjustments for multiple covariates including vascular risk factors, depressive symptoms, and medication use, following exclusions for persons with mild cognitive impairment at baseline and following exclusions for early converters to dementia. Stages of non-REM sleep were not associated with dementia risk., Conclusions: Despite contemporary interest in slow-wave sleep and dementia pathology, our findings implicate REM sleep mechanisms as predictors of clinical dementia., (© 2017 American Academy of Neurology.)

Objective: To evaluate the association between sleep duration and the risk of incident dementia and brain aging., Methods: Self-reported total hours of sleep were examined in the Framingham Heart Study (n = 2,457, mean age 72 ± 6 years, 57% women) as a 3-level variable: <6 hours (short), 6-9 hours (reference), and >9 hours (long), and was related to the risk of incident dementia over 10 years, and cross-sectionally to total cerebral brain volume (TCBV) and cognitive performance., Results: We observed 234 cases of all-cause dementia over 10 years of follow-up. In multivariable analyses, prolonged sleep duration was associated with an increased risk of incident dementia (hazard ratio [HR] 2.01; 95% confidence interval [CI] 1.24-3.26). These findings were driven by persons with baseline mild cognitive impairment (HR 2.83; 95% CI 1.06-7.55) and persons without a high school degree (HR 6.05; 95% CI 3.00-12.18). Transitioning to sleeping >9 hours over a mean period of 13 years before baseline was associated with an increased risk of all-cause dementia (HR 2.43; 95% CI 1.44-4.11) and clinical Alzheimer disease (HR 2.20; 95% CI 1.17-4.13). Relative to sleeping 6-9 hours, long sleep duration was also associated cross-sectionally with smaller TCBV (β ± SE, -1.08 ± 0.41 mean units of TCBV difference) and poorer executive function (β ± SE, -0.41 ± 0.13 SD units of Trail Making Test B minus A score difference)., Conclusions: Prolonged sleep duration may be a marker of early neurodegeneration and hence a useful clinical tool to identify those at a higher risk of progressing to clinical dementia within 10 years., (© 2017 American Academy of Neurology.)

Study Objectives: Sleep disturbances are frequently reported following traumatic brain injury (TBI); however, the exact disturbances remain unclear. This meta-analysis aimed to characterize sleep disturbance in community dwelling patients with TBI as compared to controls., Methods: Two investigators independently conducted a systematic search of multiple electronic databases from inception to May 27, 2015. Studies were selected if they compared sleep in community dwelling individuals with TBI relative to a control population without head injury. Data were pooled in meta-analysis with outcomes expressed as the standard mean difference (SMD) and 95% confidence interval (CI). The primary outcomes were derived from polysomnography and secondary outcomes were derived from subjective sleep measures., Results: Sixteen studies were included, combining 637 TBI patients and 567 controls, all of whom were community dwelling. Pooled polysomnography data revealed that TBI patients had poorer sleep efficiency (SMD = -0.47, CI: -0.89, -0.06), shorter total sleep duration (SMD = -0.37, CI: -0.59, -0.16), and greater wake after sleep onset time (SMD = 0.60, CI: 0.33, 0.87). Although sleep architecture was similar between the groups, a trend suggested that TBI patients may spend less time in REM sleep (SMD = -0.22, CI: -0.45, 0.01). Consistent with polysomnographic derangement, TBI patients reported greater subjective sleepiness and poorer perceived sleep quality., Conclusions: The evidence suggests that TBI is associated with widespread objective and subjective sleep deficits. The present results highlight the need for physicians to monitor and address sleep deficits following TBI., (© 2016 American Academy of Sleep Medicine.)