Clinical neurophysiology of apnea

The dynamics of cyclic-periodic phenomena during non-rapid and rapid eye movement sleep

Sleep is a complex physiological state characterized by distinct stages, each exhibiting unique electroencephalographic patterns and physiological phenomena. Sleep research has unveiled the presence of intricate cyclic-periodic phenomena during both non-rapid eye movement and rapid eye movement sleep stages. These phenomena encompass a spectrum of rhythmic oscillations and periodic events, including cyclic alternating pattern, periodic leg movements during sleep, respiratory-related events such as apneas, and heart rate variability. This narrative review synthesizes empirical findings and theoretical frameworks to elucidate the dynamics, interplay and implications of cyclic-periodic phenomena within the context of sleep physiology. Furthermore, it invokes the clinical relevance of these phenomena in the diagnosis and management of sleep disorders.

A systematic review with meta-analysis to assess Alzheimer's disease biomarkers in adults with or without obstructive sleep apnoea

INTRODUCTION

The aim was to design a meta-analysis evaluating the positron emission tomography (PET) uptake and cerebrospinal fluid (CSF), circulating levels of amyloid-β (Aβ), and tau proteins OSA group versus control group, as well as the association of these biomarkers with the severity of OSA.

MATERIAL AND METHODS

Four databases were searched until April 17, 2023, without any restrictions. The effect sizes were the standardized mean difference (SMD) along with a 95% confidence interval (CI).

RESULTS

A total of 21 articles were entered into the meta-analysis. The pooled SMDs of the CSF levels in OSA adults compared to controls were: -0.82 (P=0.004) for Aβ42, -1.13 (P<0.001) for Aβ40, 0.17 (P=0.23) for p-tau, 0.04 (P=0.65) for t-tau, 0.08 (P=0.89) for Aβ42/Aβ40 ratio, and 0.81 (P=0.001) for t-tau/Aβ42 ratio. The pooled SMD for the PET uptake of Aβ burden in OSA adults compared to controls was 0.30 (P=0.03). The pooled SMDs of the circulating levels in OSA adults compared to controls were: 0.67 (P=0.002) for Aβ42, 0.11 (P=0.82) for Aβ40, 0.35 (P=0.06) for p-tau, and 1.41(P=0.005) for t-tau. The pooled SMDs for levels of Aβ42, Aβ40, total Aβ, p-tau, t-tau, and Aβ42/Aβ40 ratio in severe OSA adults compared to mild/moderate OSA adults were -0.15 (P=0.33), 0.25 (P=35), 0.04 (P=87), -2.53 (P=0.24), -0.24 (P=0.52), and -0.28 (P=0.30), respectively.

CONCLUSIONS

The results indicated that CSF levels of Aβ42 and Aβ40 in OSA adults were significantly lower, but the CSF level of t-tau/Aβ42 ratio and PET Aβ burden uptake in OSA adults significantly were higher than in controls.

Pathophysiological mechanisms and therapeutic approaches in obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is a common breathing disorder in sleep in which the airways narrow or collapse during sleep, causing obstructive sleep apnea. The prevalence of OSAS continues to rise worldwide, particularly in middle-aged and elderly individuals. The mechanism of upper airway collapse is incompletely understood but is associated with several factors, including obesity, craniofacial changes, altered muscle function in the upper airway, pharyngeal neuropathy, and fluid shifts to the neck. The main characteristics of OSAS are recurrent pauses in respiration, which lead to intermittent hypoxia (IH) and hypercapnia, accompanied by blood oxygen desaturation and arousal during sleep, which sharply increases the risk of several diseases. This paper first briefly describes the epidemiology, incidence, and pathophysiological mechanisms of OSAS. Next, the alterations in relevant signaling pathways induced by IH are systematically reviewed and discussed. For example, IH can induce gut microbiota (GM) dysbiosis, impair the intestinal barrier, and alter intestinal metabolites. These mechanisms ultimately lead to secondary oxidative stress, systemic inflammation, and sympathetic activation. We then summarize the effects of IH on disease pathogenesis, including cardiocerebrovascular disorders, neurological disorders, metabolic diseases, cancer, reproductive disorders, and COVID-19. Finally, different therapeutic strategies for OSAS caused by different causes are proposed. Multidisciplinary approaches and shared decision-making are necessary for the successful treatment of OSAS in the future, but more randomized controlled trials are needed for further evaluation to define what treatments are best for specific OSAS patients.

Obstructive Apnea and Hypopnea Length in Normal Children and Adolescents

(1) Background: Breathing is an essential function that requires both metabolic (or au-tomatic) and voluntary (behavioral) control during wakefulness but during sleep depends on metabolic control via peripheral and central chemoreceptors. Breathing during sleep disordered breathing also depends on the maturity of the neural centers and the strength of the respiratory muscles. We do not know if the response to apnea varies with age. (2) Methods: We measured the obstructive apneas and hypopneas during REM and NREM in polysomnography studies from children referred for snoring. Exclusion criteria: younger than 1 year of age, neuromuscular or syndrome comorbidity, oxygen or positive airway pressure, central apnea, and studies with loss of airflow sensors. (3) Results: Two-hundred-and-sixty-eight sleep studies were included. Mean age was 8.7 years (4.68 SD), range 1–18 years, 160 were male, and 108 were female. The 5th centile of apnea duration during NREM is above 8 s at all ages, with a tendency to increase in the oldest groups up to 10 s. During REM sleep, it shows a gradual increase from 6 s in the youngest children to 10 s in the oldest. (4) Conclusions: Apnea/hypopnea length increases with age in children and adolescents independently from sex or severity of OSA. Using adult criteria in teens seems to be accurate.

Sleep-Disordered Breathing and Pregnancy-Related Cardiovascular Disease

Sleep-disordered breathing (SDB) is a serious medical condition characterized by intermittent episodes of airflow limitation, intermittent hypoxia, and sleep disturbance triggering a pattern of autonomic dysfunction associated with hypertension, diabetes, and other adverse health conditions. SDB incidence is two to three times higher during pregnancy and is associated with an increased risk of cardiometabolic complications, including pre-eclampsia and gestational diabetes. Treatments to protect breathing during sleep are available, pointing to SDB as a potential therapeutic target to reduce maternal cardiometabolic morbidity. However, in clinical practice, the majority of SDB cases in pregnancy are undiagnosed, indicating a need to improve screening for SDB risk factors and referral for diagnostic testing. Furthermore, definitive clinical trials are needed to determine the extent to which SDB intervention reduces the risk of adverse cardiovascular and neonatal outcomes in pregnancy. This review article discusses an accumulation of research pointing to SDB as a prevalent risk factor for gestational cardiometabolic disease, as well as a potential therapeutic target to reduce cardiometabolic morbidity.