Nocturnal Hypoxia and Sleep Fragmentation May Drive Neurodegenerative Processes: The Compared Effects of Obstructive Sleep Apnea Syndrome and Periodic Limb Movement Disorder on Alzheimer’s Disease Biomarkers

Analysis of sleep apnea research with a special focus on the use of positron emission tomography as a study tool

The quality of sleep plays a significant role in determining human well-being, and studying sleep and sleep disorders using various methods can aid in the prevention and treatment of diseases. Positron emission tomography (PET) is a noninvasive and highly sensitive medical imaging technique that has been widely adopted in the clinic. This review article provides data on research activity related to sleep and sleep apnea and discusses the use of PET in investigating sleep apnea and other sleep disorders. We conducted a statistical analysis of the number of original research articles published on sleep and sleep apnea between 1965 and 2021 and found that there has been a dramatic increase in publications since 1990. The distribution of contributing countries and regions has also undergone significant changes. Although there is an extensive body of literature on sleep research (256,399 original research articles during 1965-2021), PET has only been used in 54 of these published studies, indicating a largely untapped area of research. Nonetheless, PET is a useful tool for identifying connections between sleep disorders and pathological changes in various diseases, including neurological, metabolic, and cardiovascular disorders, as well as cancer. To facilitate the broader use of PET in sleep apnea research, further studies are needed in both clinical and preclinical settings.

Clinical correlates of obstructive sleep apnoea in idiopathic normal pressure hydrocephalus

BACKGROUND AND PURPOSE

The pathogenesis of idiopathic normal pressure hydrocephalus (iNPH) remains controversial. Limited studies have indicated a high prevalence of obstructive sleep apnoea (OSA) amongst iNPH patients. The aim was to investigate the clinical correlates of OSA in iNPH patients.

METHODS

In this cross-sectional observational study, consecutive iNPH patients were prospectively enrolled. Evaluations included the iNPH Rating Scale, the Movement Disorder Society Unified Parkinson's Disease Rating Scale part III, the time and number of steps to walk 10 m, the Epworth Sleepiness Scale, the Pittsburgh Sleep Quality Index, a complete neuropsychological evaluation, 3-T brain MRI, full-night video-polysomnography, tap test and cerebrospinal fluid (CSF) neurodegeneration biomarkers.

RESULTS

Fifty-one patients were screened, of whom 38 met the inclusion criteria. Amongst the recruited patients, 19/38 (50%) exhibited OSA, with 12/19 (63.2%) presenting moderate to severe disorder. OSA+ iNPH patients required more time (p = 0.02) and more steps (p = 0.04) to complete the 10-m walking test, had lower scores on the gait subitem of the iNPH Rating Scale (p = 0.04) and demonstrated poorer performance on specific neuropsychological tests (Rey Auditory Verbal Learning Test immediate recall, p = 0.03, and Rey-Osterrieth Complex Figure, p = 0.01). Additionally, OSA+ iNPH patients had higher levels of total tau (p = 0.02) and phospho-tau (p = 0.03) in their CSF but no statistically significant differences in beta-amyloid (1-42) levels compared to OSA- iNPH patients.

CONCLUSION

Obstructive sleep apnoea is highly prevalent in iNPH patients, particularly at moderate to severe levels. OSA is associated with worse motor and cognitive performance in iNPH. The CSF neurodegeneration biomarker profile observed in OSA+ iNPH patients may reflect OSA-induced impairment of cerebral fluid dynamics.

Association between sleep disorders and health care utilization in children with chronic medical conditions: a Medicaid claims data analysis

STUDY OBJECTIVES

To examine the risk of increased health care utilization (HU) linked to individual sleep disorders in children with chronic medical conditions.

METHODS

Medicaid claims data from a cohort of 16,325 children enrolled in the Coordinated Healthcare for Complex Kids (CHECK) project were used. Sleep disorders and chronic medical conditions were identified using International Classification of Diseases, Ninth, and 10th Revision, codes. Three HU groups were identified based on participants' prior hospitalizations and emergency department (ED) visits in the 12 months prior to enrollment: low (no hospitalization or ED visit), medium (1-2 hospitalizations or 1-3 ED visits), and high (≥ 3 hospitalizations or ≥ 4 ED visits). The odds of being in an increased HU group associated with specific sleep disorders after controlling for confounding factors were examined.

RESULTS

Children with chronic medical conditions and any sleep disorder had nearly twice the odds (odds ratio = 1.83; 95% confidence interval: 1.67-2.01) of being in an increased HU group compared with those without a sleep disorder. The odds of being in the increased HU group varied among sleep disorders. Only sleep-disordered breathing (odds ratio = 1.51; 95% confidence interval : 1.17-1.95), insomnia (odds ratio = 1.46; 95% confidence interval : 1.06-2.02), and circadian rhythm sleep disorder (odds ratio = 2.45; 95% confidence interval : 1.07-5.64) increased those odds. Younger age and being White were also linked to increased HU.

CONCLUSIONS

Sleep disorders are associated with increased risk of heightened HU (ED visits and/or hospitalizations) in children with chronic medical conditions. This risk varies by specific sleep disorders. These findings indicate the need for careful evaluation and management of sleep disorders in this high-risk cohort.

CITATION

Adavadkar PA, Brooks L, Pappalardo AA, Schwartz A, Rasinski K, Martin MA. Association between sleep disorders and health care utilization in children with chronic medical conditions: a Medicaid claims data analysis. J Clin Sleep Med. 2024;20(4):595-601.

Sleep disorders and Alzheimer's disease pathophysiology: The role of the Glymphatic System. A scoping review

BACKGROUND

Alzheimer's disease (AD) is highly intertwined with sleep disturbances throughout its whole natural history. Sleep consists of a major compound of the functionality of the glymphatic system, as the synchronized slow-wave activity during NREM facilitates cerebrospinal and interstitial long-distance mixing.

OBJECTIVE

The present study undertakes a scoping review of research on the involvement of the glymphatic system in AD-related sleep disturbances.

DESIGN

we searched Medline, Embase, PsychInfo and HEAL-link databases, without limitations on date and language, along with reference lists of relevant reviews and all included studies. We included in vivo, in vitro and post-mortem studies examining glymphatic implications of sleep disturbances in human populations with AD spectrum pathology. A thematic synthesis of evidence based on the extracted content was applied and presented in a narrative way.

RESULTS

In total, 70 original research articles were included and were grouped as following: a) Protein aggregation and toxicity, after sleep deprivation, along with its effects on sleep architecture, b) Glymphatic Sequalae in SDB, yielding potential glymphatic markers c) Circadian Dysregulation, d) Possible Interventions.

CONCLUSIONS

this review sought to provide insight into the role of sleep disturbances in AD pathogenesis, in the context of the glymphatic disruption.

Sleep Biomarkers for Predicting Cognitive Decline and Alzheimer's Disease: A Systematic Review of Longitudinal Studies

BACKGROUND

Sleep disturbances are considered a hallmark of dementia, and strong evidence supports the association between alterations in sleep parameters and cognitive decline in patients with mild cognitive impairment and Alzheimer's disease (AD).

OBJECTIVE

This systematic review aims to summarize the existing evidence on the longitudinal association between sleep parameters and cognitive decline, with the goal of identifying potential sleep biomarkers of AD-related neurodegeneration.

METHODS

Literature search was conducted in PubMed, Web of Science, and Scopus databases from inception to 28 March 2023. Longitudinal studies investigating the association between baseline objectively-measured sleep parameters and cognitive decline were assessed for eligibility.

RESULTS

Seventeen studies were included in the qualitative synthesis. Sleep fragmentation, reduced sleep efficiency, reduced REM sleep, increased light sleep, and sleep-disordered breathing were identified as predictors of cognitive decline. Sleep duration exhibited a U-shaped relation with subsequent neurodegeneration. Additionally, several sleep microstructural parameters were associated with cognitive decline, although inconsistencies were observed across studies.

CONCLUSIONS

These findings suggest that sleep alterations hold promise as early biomarker of cognitive decline, but the current evidence is limited due to substantial methodological heterogeneity among studies. Further research is necessary to identify the most reliable sleep parameters for predicting cognitive impairment and AD, and to investigate interventions targeting sleep that can assist clinicians in the early recognition and treatment of cognitive decline. Standardized procedures for longitudinal studies evaluating sleep and cognition should be developed and the use of continuous sleep monitoring techniques, such as actigraphy or EEG headband, might be encouraged.

Shedding light on neurofilament involvement in cognitive decline in obstructive sleep apnea and its possible role as a biomarker

Obstructive sleep apnea is one of the most common sleep disorders with a high estimated global prevalence and a large number of associated comorbidities in general as well as specific neuropsychiatric complications such as cognitive impairment. The complex pathogenesis and effects of the disorder including chronic intermittent hypoxia and sleep fragmentation may lead to enhanced neuronal damage, thereby contributing to neuropsychiatric pathologies. Obstructive sleep apnea has been described as an independent risk factor for several neurodegenerative diseases, including Alzheimer's disease and all-cause dementia. The influence of obstructive sleep apnea on cognitive deficits is still a topic of recent debate, and several mechanisms, including neurodegeneration and depression-related cognitive dysfunction, underlying this correlation are taken into consideration. The differentiation between both pathomechanisms of cognitive impairment in obstructive sleep apnea is a complex clinical issue, requiring the use of multiple and costly diagnostic methods. The studies conducted on neuroprotection biomarkers, such as brain-derived neurotrophic factors and neurofilaments, are recently gaining ground in the topic of cognition assessment in obstructive sleep apnea patients. Neurofilaments as neuron-specific cytoskeletal proteins could be useful non-invasive indicators of brain conditions and neurodegeneration, which already are observed in many neurological diseases leading to cognitive deficits. Additionally, neurofilaments play an important role as a biomarker in other sleep disorders such as insomnia. Thus, this review summarizes the current knowledge on the involvement of neurofilaments in cognitive decline and neurodegeneration in obstructive sleep apnea patients as well as discusses its possible role as a biomarker of these changes.

Obstructive sleep apnea and dementia: A role to play?

A growing number of studies, in animal models and humans, have highlighted the link between sleep and Alzheimer's disease (AD) pathophysiology. Among sleep disorders, obstructive sleep apnea (OSA) appears to be a potentially interesting comorbidity, as it is highly prevalent in the middle-aged and elderly population, often associated with some cognitive impairment, associated with an increased risk of developing cognitive decline and dementia including AD, and indeed treatable. The association between OSA and cognition varies according to the studies, but OSA is more frequent in older people with AD than those who are cognitively normal. People with OSA suffer from daytime sleepiness, impaired cognitive function and an increased risk of developing mild cognitive impairment, dementia and AD than those without OSA. Finally, the literature suggests a link between OSA and AD biomarkers. Whether screening and treating OSA could have positive impact on the levels of AD biomarkers and slow or even prevent incident dementia remain to be investigated. It therefore seems essential to understand the role of OSA in the pathophysiology of AD, as there is still no effective treatment to slow or halt its progression. At present, treating the risk factors that can promote the development and/or worsening of AD represents a promising strategy for delaying or even thwarting the onset of symptoms.

Sleep Alterations in a Mouse Model of Spinocerebellar Ataxia Type 3

Spinocerebellar ataxia type 3 (SCA3) is a neurodegenerative disorder showing progressive neuronal loss in several brain areas and a broad spectrum of motor and non-motor symptoms, including ataxia and altered sleep. While sleep disturbances are known to play pathophysiologic roles in other neurodegenerative disorders, their impact on SCA3 is unknown. Using spectrographic measurements, we sought to quantitatively characterize sleep electroencephalography (EEG) in SCA3 transgenic mice with confirmed disease phenotype. We first measured motor phenotypes in 18-31-week-old homozygous SCA3 YACMJD84.2 mice and non-transgenic wild-type littermate mice during lights-on and lights-off periods. We next implanted electrodes to obtain 12-h (zeitgeber time 0-12) EEG recordings for three consecutive days when the mice were 26-36 weeks old. EEG-based spectroscopy showed that compared to wild-type littermates, SCA3 homozygous mice display: (i) increased duration of rapid-eye movement sleep (REM) and fragmentation in all sleep and wake states; (ii) higher beta power oscillations during REM and non-REM (NREM); and (iii) additional spectral power band alterations during REM and wake. Our data show that sleep architecture and EEG spectral power are dysregulated in homozygous SCA3 mice, indicating that common sleep-related etiologic factors may underlie mouse and human SCA3 phenotypes.

The Association Between Erectile Dysfunction and Sleep Parameters: Data from a Prospective, Controlled Cohort

BACKGROUND

Many studies have reported a possible strong relationship between poor sleep quality, sleep disruption, sleep disorders, and erectile dysfunction (ED).

AIM

This study aimed to investigate the relationship between sleep quality and ED.

METHODS

Patients diagnosed with ED by the International Index of Erectile Function-5 (IIEF-5) questionnaire and 72 healthy adult men were included. Participants completed the questionnaire, underwent a detailed physical examination, and provided blood samples. All enrolled subjects then wore the Fitbit Charge 2 that monitored sleep throughout the night.

OUTCOMES

Primary outcome measures included scores on the IIEF-5, General Anxiety Disorder-7 (GAD-7) scale, Patient Health Questionnaire-9 (PHQ-9), Pittsburgh Sleep Quality Index (PSQI), and sleep monitoring parameters obtained from Fitbit Charge 2.

RESULTS

Finally, a total of 107 ED patients and 72 healthy adult men were enrolled in this study. Univariate analysis indicated that the GAD-7 (P < .001), PHQ-9 (P < .001), and PSQI scores (P < .001) significantly differed according to the presence/absence of ED. Further multiple logistic regression analysis showed that the PHQ-9 (odds ratio [OR]: 1.227, 95% confidence interval [CI]: 1.070-1.407; P = .003) and PSQI scores (OR: 1.220, 95%CI: 1.116-1.334; P < .001) were independent risk factors for ED. Analysis of objective sleep monitoring parameters showed that total sleep time (TST) (P = .001), sleep onset latency (SOL) (P = .026), deep sleep (N3) duration (P = .011) and rapid eye movement (REM) sleep duration (P < .001) were significantly differed between the 2 groups, with durations in the ED group significantly lower than those in the non-ED group. In addition, receiver operating characteristic (ROC) curve analysis indicated that the REM sleep duration had the highest area under the curve (AUC: 0.728) of all sleep parameters, with a P value < .001, a sensitivity of 72.2% and a specificity of 73.8%.

CLINICAL IMPLICATIONS

Urologists and andrologists should be aware of impacted sleep quality and depression in ED patients.

STRENGTHS & LIMITATIONS

The strength of this study is that the relationship between sleep quality and ED was assessed with both a subjective scale and an objective sleep monitoring tool. However, our study only described an association between sleep quality and ED and did not establish a causal relationship.

CONCLUSION

Sleep parameters are strongly associated with ED, indicating that poor sleep quality may increase the likelihood of ED. Wu X, Zhang Y, Zhang W, et al. The Association Between Erectile Dysfunction and Sleep Parameters: Data from a Prospective, Controlled Cohort. J Sex Med 2022;XX:XXX-XXX.