Estimated respiratory arousal threshold in patients with rapid eye movement obstructive sleep apnea

Sex differences in sleep and sleep-disordered breathing

PURPOSE OF REVIEW

There is increasing evidence for relevant sex differences in pathophysiology, symptom presentation and outcomes in obstructive sleep apnoea (OSA). However, research on sex differences and sex-specific phenotypes in sleep-disordered breathing (SDB) is still in its infancy and data on sex differences in other SDB is still very scarce.

RECENT FINDINGS

While OSA is more common in men than in premenopausal women, the prevalence of OSA doubles postmenopausally and becomes comparable to that of men. Women have a lower collapsibility of the upper airway and a lower arousal threshold. In addition, the rapid eye movement (REM)-apnoea-hypopnoea index (AHI) is typically higher in women than in men, but the non-REM-AHI and thus the total AHI is often lower. Women are often symptomatic at lower AHI and present more frequently with symptoms of sleep fragmentation and poor sleep quality. Both certain forms of OSA (e.g. REM-OSA) and certain phenotypes (e.g. COMISA) are more common in women. Men have a higher risk of high loop gain central sleep apnoea.

SUMMARY

For a better understanding of sex-typical phenotypes with the aim of a more targeted treatment approach of SDB, adequately powered studies on sex differences in SDB should be conducted.

Low arousal threshold is associated with altered functional connectivity of the ascending reticular activating system in patients with obstructive sleep apnea

A low arousal threshold (LAT) is a pathophysiological trait of obstructive sleep apnea (OSA) that may be associated with brainstem ascending reticular activating system-cortical functional connectivity changes. We evaluated resting-state connectivity between the brainstem nuclei and 105 cortical/subcortical regions in OSA patients with or without a LAT and healthy controls. Twenty-five patients with moderate to severe OSA with an apnea-hypopnea index between 20 and 40/hr (15 with and 10 without a LAT) and 15 age- and sex-matched controls were evaluated. Participants underwent functional magnetic resonance imaging after overnight polysomnography. Three brainstem nuclei-the locus coeruleus (LC), laterodorsal tegmental nucleus (LDTg), and ventral tegmental area (VTA)-associated with OSA in our previous study were used as seeds. Functional connectivity values of the two brainstem nuclei (LC and LDTg) significantly differed among the three groups. The connectivity of the LC with the precuneus was stronger in OSA patients than in controls regardless of the concomitant LAT. The connectivity between the LDTg and the posterior cingulate cortex was also stronger in OSA patients regardless of the LAT. Moreover, OSA patients without a LAT showed stronger LDTg-posterior cingulate cortex connectivity than those with a LAT (post hoc p = 0.013), and this connectivity strength was negatively correlated with the minimum oxygen saturation in OSA patients (r = - 0.463, p = 0.023). The LAT in OSA patients was associated with altered LDTg-posterior cingulate cortex connectivity. This result may suggested that cholinergic activity may play a role in the LAT in OSA patients.

Rapid eye movement dependency is associated with increased inflammatory activity in obstructive sleep apnea syndrome

OBJECTIVE

Rapid eye movement (REM)-dependent obstructive sleep apnea syndrome (OSAS) is a specific subtype of OSAS having some phenotypic characteristics like a preference for a younger age, female gender, and milder severity. Such favorable features could make it possible to consider an overall benign course for this phenotype. However, accumulating data introduced its association with several cardiometabolic and vascular disorders recently. The primary objective of this study was to address the disease from the inflammation perspective and evaluate the potential inflammatory status in this variant via two accessible blood parameters: platelet distribution width (PDW) and systemic immune-inflammation index (SII). The secondary aim was to investigate whether this status, together with other disease characteristics, demonstrates consistency under different definitions of REM-dependent OSAS published previously.

PATIENTS AND METHODS

The medical records of 35 patients with mild-to-moderate REM-dependent OSAS, 35 age- and sex-matched patients with REM-independent OSAS, and 25 non-OSA controls were retrospectively analyzed. Baseline features, polysomnographic characteristics, PDW, and SII were compared between the groups. Secondly, the analyses were repeated using different definitions of REM-dependent OSAS. Bivariate analyses were performed, and a multiple stepwise regression model was applied to adjust for body mass index (BMI) and cardiovascular risk (CVR) factors.  RESULTS: Mean PDW and SII were increased in patients with REM-dependent OSAS as compared to non-OSA controls (p = .022 and .029). The significance remained stable after adjustment for BMI and CVRs and was consistent according to different definitions. The Comparison of patients with REM-independent OSAS and non-OSA controls, as well as the two different subtypes of OSAS, did not yield significance.

CONCLUSION

Based on the current findings, patients with REM-dependent OSAS appear to be susceptible to inflammation and should be carefully monitored for the negative consequences of that issue. To our knowledge, this study is the first to evaluate SII and PDW in REM-dependent OSAS.

Impaired declarative memory consolidation in children with REM sleep-related obstructive sleep apnea

STUDY OBJECTIVES

We explored whether declarative memory consolidation is impaired in children with rapid eye movement sleep-related obstructive sleep apnea (REM-OSA) and investigated the correlation between memory consolidation and sleep-related respiratory parameters.

METHODS

Participants were children with habitual snoring aged 6-14 years and control children. Participants underwent polysomnography and declarative memory testing. Participants with snoring were categorized as primary snoring (PS), non-rapid eye movement sleep-related obstructive sleep apnea (NREM-OSA), stage-independent (SI)-OSA, and REM-OSA according to obstructive apnea-hypopnea index (OAHI), OAHI in REM sleep (OAHIREM), and OAHI in NREM sleep (OAHINREM). Declarative memory consolidation level was assessed by recall and recognition rates.

RESULTS

There were 34 controls and 228 children with sleep-disordered breathing: 73 PS, 48 NREM-OSA, 59 SI-OSA, and 48 REM-OSA. Total arousal index was lower in the REM-OSA group than in the NREM-OSA group. In all groups, retest scores were higher than immediate test scores. Recall consolidation in PS, SI-OSA, and REM-OSA groups was lower than for controls and lower in REM-OSA than in NREM-OSA. There were no correlations between recall consolidation or recognition consolidation and OAHI, OAHINREM, oxygen desaturation index in REM sleep, total arousal index, or REM sleep percent. Recognition consolidation was negatively correlated with OAHIREM.

CONCLUSIONS

Memory consolidation is impaired in children with REM-OSA compared with NREM-OSA and controls. There was no significant correlation between memory consolidation and OAHI, and recognition consolidation was negatively correlated with OAHIREM. It is important to pay attention to the OSA subtype in children.

CITATION

Tang Y, Yang C, Wang C, Wu Y, Xu Z, Ni X. Impaired declarative memory consolidation in children with REM sleep-related obstructive sleep apnea. J Clin Sleep Med. 2024;20(3):417-425.

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.

Neurocognitive, mood changes, and sleepiness in patients with REM-predominant obstructive sleep apnea

PURPOSE

This article focuses on recent evidence linking rapid eye movement (REM) obstructive sleep apnea (OSA) (REM-OSA) to neurocognitive dysfunction and mood changes; the proposed mechanisms for increased risk of neurocognitive dysfunction in REM-OSA, and future research prospects.

METHODS

PubMed and Google Scholar records were examined for articles utilizing pre-defined keywords. In this work, we mainly included studies published after 2017; nevertheless, critical studies published prior to 2017 were considered.

RESULTS

REM-OSA is an under-recognized stage-related sleep-disordered breathing in which obstructive respiratory events happen chiefly in stage REM. The disorder is commonly seen amongst younger patients and females and has recently been linked to cardiometabolic complications. Although less symptomatic than non-REM-OSA and non-stage-specific OSA, current findings indicate that REM-OSA may have neurocognitive repercussions and mood changes and could be linked to insomnia, increased dreams, and nightmares.

CONCLUSION

Currently available evidence indicates that REM-OSA may present with insomnia and nightmares and could affect cognitive function and mood.

Long-term outcomes regarding arterial stiffness and carotid artery atherosclerosis in female patients with rapid eye movement obstructive sleep apnea

Objective

Rapid eye movement (REM) obstructive sleep apnea (OSA) is associated with the risk of cardiovascular events. Arterial stiffness and carotid artery intima-media thickness (IMT) predict these events, but few relevant studies have been conducted. We compared long-term changes in arterial stiffness and IMT between patients with REM OSA and non-REM (NREM) OSA receiving continuous positive airway pressure (CPAP) or oral appliance (OA) therapy.

Methods

Newly diagnosed female patients with OSA received CPAP (n = 6) or OA (n = 7). Pulse wave velocity (PWV) and carotid artery ultrasound were performed before and 60 months after treatment.

Results

There were no differences in baseline characteristics (mean age: 56.0 vs. 61.3 years; mean body mass index: 22.6 vs. 21.7 kg/m²) between the REM OSA and non-REM OSA groups. The median apnea-hypopnea index was lower in the REM OSA group than in the non-REM OSA group. Increased PWV (12.92 ± 1.64 to 14.56 ± 2.73 m/s) and deteriorated glucose metabolism were observed in the REM OSA group after treatment. PWV, IMT, and cardiovascular risk factors were unaffected in the non-REM OSA group.

Conclusion

Arterial stiffness and glucose metabolism are deteriorated in patients with REM OSA compared with these parameters in patients with non-REM OSA after CPAP or OA treatment.

Association of traffic air pollution with severity of obstructive sleep apnea in urban areas of Northern Taiwan: A cross-sectional study

BACKGROUND

Although recent studies have indicated an association between obstructive sleep apnea (OSA) and air pollution, they have reported inconsistent results. Moreover, few studies investigated the effects of short-term air pollution exposure.

OBJECTIVE

To estimate the health effects of short- and long-term exposure to traffic air pollution on mild OSA in Taipei.

METHODS

We collected participants' data from Taipei Sleep Center and air pollution data from Taiwan Environmental Protection Administration. A spatiotemporal model was used to estimate the individual exposure level. Generalized linear models were used to assess the percent change of overall apnea-hypopnea index (AHI), AHI in rapid eye movement period (AHI-REM), AHI in non-REM (AHI-NREM), and oxygen desaturation index (ODI) associated with an interquartile (IQR) increase in personal pollution exposure. A generalized logistic model was used to estimate the ORs of different severities of OSA compared with the reference group.

RESULTS

In the patients with AHI of <15, both short- and long-term exposure to NO₂ were significantly associated with AHI and ODI increases: an IQR increase in 2-year mean NO₂ increased 7.3% of AHI and 8.4% of ODI; these values were the highest among all exposure windows. The effects of NO₂ on AHI increase were stronger in the men and younger patients. Moreover, the association between AHI and NO₂ in the patients with AHI of <15 was mediated by the REM stage. NO₂ exposure was associated with an increased risk of mild OSA that reached up to 24.8% per IQR increase in NO₂ averaged over 2 years. PM_2.5 exerted no effects on AHI, but an IQR increase in 1-year and 2-year mean PM_2.5 was associated with 6.8% and 8.8% increases in ODI, respectively.

CONCLUSIONS

Both short- and long-term exposure to traffic air pollution were associated with the risk of mild OSA, which was modified by REM stage.

Clinical Characteristics of Rapid Eye Movement-Related Obstructive Sleep Apnea: An Experience in a Tertiary Medical Center of Taiwan

PURPOSE

Obstructive sleep apnea (OSA) is characterized by intermittent hypoxemia and sleep fragmentation. While apnea is pronounced with severe desaturation during rapid eye movement (REM) sleep, REM-related OSA is a distinct phenotype of OSA associated with respiratory disturbances predominantly during REM sleep. In this study, we investigated the clinical features of REM-related OSA in Taiwan.

PATIENTS AND METHODS

All patients diagnosed with OSA in the Taipei Veterans General Hospital from 2015 to 2017 were analyzed retrospectively and classified into REM-related OSA (REM-OSA) group, non-REM related OSA (NREM-OSA) group, and non-stage specific-OSA group. The clinical demographics, OSA-related symptoms, polysomnography results, and medical comorbidities of the three groups were analyzed.

RESULTS

Among 1331 patients with OSA, 414 (31.1%) were classified as REM-OSA, 808 (60.7%) as NREM-OSA, and 109 (8.2%) as non-stage specific-OSA. After being adjusted for OSA severity, the REM-OSA group was associated with less portion of males, longer desaturation duration, and lower nadir oxygen saturation (SpO₂) compared with the NREM-OSA group in mild and moderate OSA. In moderate OSA, the non-stage specific-OSA group featured more OSA severity and more desaturation compared with the other groups. The Epworth Sleepiness Scale scores and the prevalence of comorbidities did not vary among the REM-OSA, NREM-OSA, and non-stage specific-OSA groups. High REM-AHI/NREM-AHI ratio was associated with young age, female gender, high BMI, and low AHI.

CONCLUSION

OSA patients with high REM-AHI/NREM-AHI ratio are related to young age, female gender, high BMI, and low AHI. Patients with REM-related OSA presented with longer desaturation duration and lower nadir SpO2 after being adjusted for OSA severity.

Nocturnal Blood Pressure Fluctuations in Patients with Rapid Eye Movement-Related Obstructive Sleep Apnea

Rapid eye movement-related obstructive sleep apnea (REM-related OSA) is a polysomnographic phenotype. Nocturnal blood pressure (BP) fluctuations remain unclear in patients with REM-related OSA. We studied 27 patients with REM-related OSA, categorized as having REM-apnea-hypopnea index (REM-AHI) ≥ 5/h, REM-AHI/non-REM-AHI ≥ 2, and non-REM-AHI < 15/h. Beat-to-beat systolic BP (SBP) variability and nocturnal SBP fluctuation patterns using pulse transit time (PTT) were investigated. The maximum increase and average nocturnal SBP were significantly higher in males than in females (p = 0.003 and p = 0.008, respectively). The rate of non-dipping patterns in nocturnal SBP fluctuations was 63% in all patients (males, 70%; females, 50%). Epworth Sleepiness Scale (ESS) and Self-rating Depression Scale (SDS) scores in females were higher than those in males (8.4 ± 6.1 vs. 13.4 ± 5.4 points, p = 0.04; 43.8 ± 7.9 vs. 52 ± 11.6 points, p = 0.04, respectively). A high proportion of patients with REM-related OSA had a non-dipping pattern. Using PPT, we observed that in patients with REM-related OSA, SBP variability was greater in males. Despite clinical symptoms being slightly more severe in females, nocturnal SBP fluctuations should be considered in male patients with REM-related OSA.