Sleep respiratory disturbances and arousals at moderate altitude have overlapping electroencephalogram spectral signatures

An ascent to altitude has been shown to result in more central apneas and a shift towards lighter sleep in healthy individuals. This study employs spectral analysis to investigate the impact of respiratory disturbances (central/obstructive apnea and hypopnea or periodic breathing) at moderate altitude on the sleep electroencephalogram (EEG) and to compare EEG changes resulting from respiratory disturbances and arousals. Data were collected from 51 healthy male subjects who spent 1 night at moderate altitude (2590 m). Power density spectra of Stage 2 sleep were calculated in a subset (20) of these participants with sufficient artefact‐free data for (a) epochs with respiratory events without an accompanying arousal, (b) epochs containing an arousal and (c) epochs of undisturbed Stage 2 sleep containing neither arousal nor respiratory events. Both arousals and respiratory disturbances resulted in reduced power in the delta, theta and spindle frequency range and increased beta power compared to undisturbed sleep. The similarity of the EEG changes resulting from altitude‐induced respiratory disturbances and arousals indicates that central apneas are associated with micro‐arousals, not apparent by visual inspection of the EEG. Our findings may have implications for sleep in patients and mountain tourists with central apneas and suggest that respiratory disturbances not accompanied by an arousal may, none the less, impact sleep quality and impair recuperative processes associated with sleep more than previously believed.     

Case-control study of subjective and objective differences in sleep patterns in older adults with insomnia symptoms

Older adults have high prevalence rates of insomnia symptoms, yet it is unclear if these insomnia symptoms are associated with objective impairments in sleep. We hypothesized that insomnia complaints in older adults would be associated with objective differences in sleep compared with those without insomnia complaints. To test this hypothesis, we conducted a cross‐sectional study in which older adults with insomnia complaints (cases, n = 100) were compared with older adults without insomnia complaints (controls, n = 100) using dual‐night in‐lab nocturnal polysomnography, study questionnaires and 7 days of at‐home actigraphy and sleep diaries. Cases were noted to have reduced objective total sleep time compared with controls (25.8 ± 8.56 min, P = 0.003). This was largely due to increased wakefulness after sleep onset, and not increased sleep latency. When participants with sleep‐related breathing disorder or periodic limb movement disorder were excluded, the polysomnography total sleep time difference became even larger. Cases also had reduced slow‐wave sleep (5.10 ± 1.38 min versus 10.57 ± 2.29 min, effect size −0.29, P = 0.04). When comparing self‐reported sleep latency and sleep efficiency with objective polysomnographic findings, cases demonstrated low, but statistically significant correlations, while no such correlations were observed in controls. Cases tended to underestimate their sleep efficiency by 1.6% (±18.4%), while controls overestimated their sleep efficiency by 12.4% (±14.5%). In conclusion, we noted that older adults with insomnia complaints have significant differences in several objective sleep findings relative to controls, suggesting that insomnia complaints in older adults are associated with objective impairments in sleep.     

Lung volumes and mean apnea duration in obstructive sleep apnea

Former studies suggested that lung volumes might play a role in pathomechanisms of obstructive sleep apnea (OSA). Mean apnea duration (MAD) is a rarely investigated parameter in OSA but is possibly a surrogate of arousal threshold. The aim of this study was to evaluate the influence of lung volumes to MAD in OSA. In 69 patients with obstructive sleep apnea (51 male und 18 female, BMI 34.2 ± 6.0 kg/m², age 53.6 ± 9.7 years, AHI 43.1 ± 21.1/h) we performed a polysomnography and pulmonary function testing in daytime. There was a significant correlation between MAD and residual volume (RV) (r = 0.51; p < 0.001), which was the highest correlation we found. In linear regression analysis RV remained the only independent variable with significant influence on MAD (p < 0.001). We could show that RV seems to play a role in the mechanisms of apnea termination in terms of MAD. MAD reflects the time until a specific negative intrathoracic pressure is reached to induce an arousal. In this process dependency on RV could explain our results. Despite some limitations these results provide some new aspects in understanding pathophysiology of OSA.     

成年阻塞性睡眠呼吸暂停患者多导睡眠图及临床特征分析性差异

目的:分析成年男性阻塞性睡眠呼吸暂停(OSA)患者多导睡眠图及临床特征,明确年龄对OSA严重程度的影响。方法:回顾性研究包括836名成年男性OSA患者,按年龄分为三组:青年组312人(平均年龄37.07岁),中年组359人(平均年龄52.14岁),老年组165人(平均年龄69.43岁)。分析其多导睡眠图和临床特征,并进行相关性分析。结果:中年组和老年组呼吸暂停低通气指数(AHI)、阻塞性呼吸暂停指数(OAI)、AHI-NREM和AHI-REM均无显著统计学意义(P>0.05),但均低于青年组(P<0.01);中年组和老年组的最低血氧饱和度(SaO2)均高于青年组;中枢性呼吸暂停指数(CAI)随年龄增长而升高(P<0.05)。在睡眠结构方面,老年组总睡眠时间、非快速眼动(NREM)睡眠时间和快速眼动期(REM)睡眠时间均缩短,睡眠效率亦低于青年组(P<0.01),但睡眠潜伏期和入睡后觉醒时间(WASO)明显延长(P<0.01)。年龄与以下各项均呈现显著的相关性:AHI(P<0.01),OAI(P<0.01),CAI(P<0.01),最低SaO2(P<0.01)。多重回归分析表明年龄作为独立变量分别与AHI,OAI,CAI具有相关性。结论:在成年OSA患者中,年龄与OSA严重程度具有显著的相关性,表现为OSA随年龄增长而降低。本研究为研究年龄与OSA严重程度的关系提供了新的证据。     

Obstructive sleep apnea treatment and dementia risk in older adults

Study ObjectivesTo examine associations between positive airway pressure (PAP) therapy, adherence and incident diagnoses of Alzheimer’s disease (AD), mild cognitive impairment (MCI), and dementia not otherwise specified (DNOS) in older adults.MethodsThis retrospective study utilized Medicare 5% fee-for-service claims data of 53,321 beneficiaries, aged 65 and older, with an obstructive sleep apnea (OSA) diagnosis prior to 2011. Study participants were evaluated using ICD-9 codes for neurocognitive syndromes (AD [n = 1,057], DNOS [n = 378], and MCI [n = 443]) that were newly identified between 2011 and 2013. PAP treatment was defined as the presence of at least one durable medical equipment (Healthcare Common Procedure Coding System [HCPCS]) code for PAP supplies. PAP adherence was defined as at least two HCPCS codes for PAP equipment, separated by at least 1 month. Logistic regression models, adjusted for demographic and health characteristics, were used to estimate associations between PAP treatment or adherence and new AD, DNOS, and MCI diagnoses.ResultsIn this sample of Medicare beneficiaries with OSA, 59% were men, 90% were non-Hispanic whites and 62% were younger than 75 years. The majority (78%) of beneficiaries with OSA were prescribed PAP (treated), and 74% showed evidence of adherent PAP use. In adjusted models, PAP treatment was associated with lower odds of incident diagnoses of AD and DNOS (odds ratio [OR] = 0.78, 95% confidence interval [95% CI]: 0.69 to 0.89; and OR = 0.69, 95% CI: 0.55 to 0.85). Lower odds of MCI, approaching statistical significance, were also observed among PAP users (OR = 0.82, 95% CI: 0.66 to 1.02). PAP adherence was associated with lower odds of incident diagnoses of AD (OR = 0.65, 95% CI: 0.56 to 0.76).ConclusionsPAP treatment and adherence are independently associated with lower odds of incident AD diagnoses in older adults. Results suggest that treatment of OSA may reduce the risk of subsequent dementia.     

Swallowing and aspiration during sleep in patients with obstructive sleep apnea versus control individuals

Study ObjectivesThere are only a few reports on voluntary swallowing during sleep; therefore, this study aimed to propose a method for observing voluntary swallowing during sleep using polysomnography. The frequency of voluntary swallowing during sleep and the factors related to swallowing and aspiration during sleep were investigated.MethodsPolysomnography records of 20 control subjects and 60 patients with obstructive sleep apnea (OSA) (mild, moderate, and severe groups; n = 20 each) were collected. Simultaneous increases in the electromyographic potentials of the submental and masseter muscles, termed coactivation, and declining oronasal airflow (SA) were extracted as “swallowing.” The cough reflex that occurred during sleep was extracted as “aspiration.” The frequency of swallowing events was compared among the different OSA severity groups. Subsequently, a multivariate regression analysis was performed.ResultsThe average frequency of coactivation with SA in control subjects was 4.1 events/h and that without SA was 1.7 events/h. These frequencies increased with the severity of OSA during non-REM sleep. The distance of the hyoid to the Frankfurt plane was associated with the frequency of coactivation with (β = 0.298, p = 0.017) as well as without SA (β = 0.271, p = 0.038). The frequency of coactivation without SA was associated with aspiration (B = 0.192, p = 0.042).ConclusionsOur data provide new insights into the relationship between swallowing and aspiration during sleep. We found that the longer the distance from the hyoid bone to the Frankfurt plane, the higher the coactivation without SA, which could lead to aspiration during sleep.Clinical TrialsRetrospective observational study of swallowing during sleep in obstructive sleep apnea patients using polysomnography, https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000050460, UMIN000044187.     

Sleepiness and residual sleepiness in adults with obstructive sleep apnea

Sleepiness is a common, but not necessary symptom of the obstructive sleep apnea syndrome (OSA) and is a frequent chief complaint of patients with OSA who seek medical attention. While sleepiness may seem simple in nature, the underlying mechanisms producing daytime sleepiness in OSA are complex and poorly characterized. Moreover, the meaningful assessment of pathological sleepiness is frequently far from straightforward. Effective treatment of OSA is generally expected to resolve or ameliorate daytime sleepiness. An unknown percentage of treated OSA patients, however, remain sleepy during waking hours. The assessment and treatment of residual sleepiness in treated OSA can range from simple to difficult, depending on the nature and causes of the continued sleepiness. Recently, however, data from clinical trials have been generated which provide direction in the evaluation and management of the OSA patient suffering residual daytime sleepiness.     

Dynamic tongue area measurements in ultrasound images for adults with obstructive sleep apnea

Obstructive sleep apnea is a chronic breathing disorder where the recursive collapse of the upper airway causes cessation of airflow during sleep. Quantitative assessments of dynamic tongue motion may provide a better understanding of the mechanism of obstructive sleep apnea. Tongue area changes, in submental ultrasound images recorded during wakefulness from normal breathing by the Müller manoeuvre, were tracked using the modified optical flow‐based method. The results demonstrated that patients with obstructive sleep apnea had a larger mid‐sagittal tongue area compared to the control group (during normal breathing, p = .004, during the Müller manoeuvre p = .005, and differences between normal breathing and the Müller manoeuvre, p = .01). Tongue area measurements were significantly different in patients with varying severity of OSA during normal breathing and during the Müller manoeuvre, and had differences between normal breathing and the Müller manoeuvre (p = .005, p = .008 and p = .03, respectively). Patients with moderate or severe obstructive sleep apnea exhibited minimal movement of the tongue. In contrast, normal controls and patients with mild obstructive sleep apnea demonstrated bidirectional tongue motions during a transition from normal breathing to the Müller manoeuvre in wakefulness. Identifying different patterns of deformation and displacement of the tongue may have potential in evaluating the presence and the pathogenesis of OSA.     

Prevalence and correlates of sleep apnea among US Veterans with chronic kidney disease

The prevalence and correlates of sleep apnea (SA) among Veterans with chronic kidney disease (CKD), a population at high risk of both SA and CKD, are unknown. We performed a cross‐sectional analysis of 248 Veterans (18–89 years) selected only for presence of moderate to severe CKD. All participants underwent full, unattended polysomnography, measurement of renal function and a sleepiness questionnaire. Logistic regression with backward selection was used to identify predictors of prevalent SA (apnea–hypopnea index [AHI, ≥15 events/hr] and prevalent nocturnal hypoxia [NH, % of total sleep time spent at <90% oxygen saturation]). The mean age of our cohort was 73.2 ± 9.6 years, 95% were male, 78% were Caucasian and the mean body mass index (BMI) was 30.3 ± 4.8 kg/m². The prevalence of SA was 39%. There was no difference in daytime sleepiness among those with and without SA. In the final model, older age, higher BMI and diabetes mellitus (DM) were associated with higher odds of SA, after controlling for age, BMI, race and sex. Higher BMI, DM, unemployed/retired status, current smoking and higher serum bicarbonate level were associated with prevalent NH. To sum, SA was common among Veterans with moderate to severe CKD. Although some traditional risk factors for SA were associated with SA in this population, sleepiness did not correlate with SA. Further study is needed to validate our findings and understand how best to address the high burden of SA among Veterans with CKD.     

Electric field aspects in hypoglossal nerve stimulation for obstructive sleep apnea: A bilateral electrophysiological evaluation of unilateral electrode configuration changes

Hypoglossal nerve stimulation is an established treatment option for obstructive sleep apnea in selected patients. A unilateral hypoglossal nerve stimulation system was approved a decade ago, yet the physiological effect of unilateral hypoglossal stimulation on bilateral tongue motion remains unclear. This study examined how electrode configuration, stimulation cuff position, or body mass index influenced the contralateral genioglossus electromyography (EMG) signal. Twenty-nine patients underwent three EMG recordings in a polysomnographic setting after being implanted with a unilateral hypoglossal nerve stimulator for at least 6 months. The ratio of EMG signals between the ipsi- and contralateral sides was evaluated. No difference in EMG signals was demonstrated based on electrode configurations, stimulation-cuff position, body-mass-index, or sleep apnea severity, even in patients with right tongue protrusion only. Our findings may be explained by a significant level of cross-innervation and by a smaller and less variable circumferential electric field than expected based on prior biophysical models. A patient's individual anatomy needs to be considered during therapy titration in order to achieve an optimal response.     

Brain temperature dependent changes in the electroencephalogram power spectrum of humans and animals

In animals, changes in brain temperature induce a shift in frequencies in the electroencephalogram (EEG). Given the large decreases in body and brain temperature that occur during hibernation, putative functions that were previously ascribed to certain EEG frequencies are no longer valid because of the progressive shift away from the original frequency. In the present review it is proposed that even moderate temperature changes in humans and animals, such as those across the circadian or menstrual cycle, or induced by drugs, have a significant effect on EEG frequencies and the corresponding power spectrum. Alterations in the relative EEG power spectrum, in studies where body temperature also changes, may not be a direct cause of the treatment under investigation, but a consequence of effects on body or brain temperature. However, these effects on the EEG power spectrum are usually interpreted to result directly from the experimental treatment.     

Estimating daytime sleepiness with previous night electroencephalography,electrooculography, and electromyography spectrograms in patients with suspected sleep apnea using a convolutional neural network

A common symptom of obstructive sleep apnea (OSA) is excessive daytime sleepiness (EDS). The gold standard test for EDS is the multiple sleep latency test (MSLT). However, due to its high cost, MSLT is not routinely conducted for OSA patients and EDS is instead evaluated using sleep questionnaires. This is problematic however, since sleep questionnaires are subjective and correlate poorly with the MSLT. Therefore, new objective tools are needed for reliable evaluation of EDS. The aim of this study was to test our hypothesis that EDS can be estimated with neural network analysis of previous night polysomnographic signals. We trained a convolutional neural network (CNN) classifier using electroencephalography, electrooculography, and chin electromyography signals from 2,014 patients with suspected OSA. The CNN was trained to classify the patients into four sleepiness categories based on their mean sleep latency (MSL); severe (MSL < 5min), moderate (5 ≤ MSL < 10), mild (10 ≤ MSL < 15), and normal (MSL ≥ 15). The CNN classified patients to the four sleepiness categories with an overall accuracy of 60.6% and Cohen’s kappa value of 0.464. In two-group classification scheme with sleepy (MSL < 10 min) and non-sleepy (MSL ≥ 10) patients, the CNN achieved an accuracy of 77.2%, with sensitivity of 76.5%, and specificity of 77.9%. Our results show that previous night’s polysomnographic signals can be used for objective estimation of EDS with at least moderate accuracy. Since the diagnosis of OSA is currently confirmed by polysomnography, the classifier could be used simultaneously to get an objective estimate of the daytime sleepiness with minimal extra workload.     

Prevalence and association analysis of obstructive sleep apnea with gender and age differences – Results of SHIP‐Trend

Identification of obstructive sleep apnea and risk factors is important for reduction in symptoms and cardiovascular risk, and for improvement of quality of life. The population‐based Study of Health in Pomerania investigated risk factors and clinical diseases in a general population of northeast Germany. Additional polysomnography was applied to measure sleep and respiration with the objective of assessing prevalence and risk factors of obstructive sleep apnea in a German cohort. One‐thousand, two‐hundred and eight people between 20 and 81 years old (54% men, median age 54 years) underwent overnight polysomnography. The estimated obstructive sleep apnea prevalence was 46% (59% men, 33% women) for an apnea–hypopnea index ≥5%, and 21% (30% men, 13% women) for an apnea–hypopnea index ≥ 15. The estimated obstructive sleep apnea syndrome prevalence (apnea–hypopnea index ≥5; Epworth Sleepiness Scale >10) was 6%. The prevalence of obstructive sleep apnea continuously increased with age for men and women with, however, later onset for women. Gender, age, body mass index, waist‐to‐hip ratio, snoring, alcohol consumption (for women only) and self‐reported cardiovascular diseases were significantly positively associated with obstructive sleep apnea, whereas daytime sleepiness was not. Diabetes, hypertension and metabolic syndrome were positively associated with severe obstructive sleep apnea. The associations became non‐significant after adjustment for body mass. Women exhibited stronger associations than men. The prevalence of obstructive sleep apnea was high, with almost half the population presenting some kind of obstructive sleep apnea. The continuous increase of obstructive sleep apnea with age challenges the current theory that mortality due to obstructive sleep apnea and cardiovascular co‐morbidities affect obstructive sleep apnea prevalence at an advanced age. Also, gender differences regarding obstructive sleep apnea and associations are significant for recognizing obstructive sleep apnea mechanisms and therapy responsiveness.     

The effects of sleep deprivation in humans: topographical electroencephalogram changes in non‐rapid eye movement (NREM) sleep versus REM sleep

Studies on homeostatic aspects of sleep regulation have been focussed upon non‐rapid eye movement (NREM) sleep, and direct comparisons with regional changes in rapid eye movement (REM) sleep are sparse. To this end, evaluation of electroencephalogram (EEG) changes in recovery sleep after extended waking is the classical approach for increasing homeostatic need. Here, we studied a large sample of 40 healthy subjects, considering a full‐scalp EEG topography during baseline (BSL) and recovery sleep following 40 h of wakefulness (REC). In NREM sleep, the statistical maps of REC versus BSL differences revealed significant fronto‐central increases of power from 0.5 to 11 Hz and decreases from 13 to 15 Hz. In REM sleep, REC versus BSL differences pointed to significant fronto‐central increases in the 0.5–7 Hz and decreases in the 8–11 Hz bands. Moreover, the 12–15 Hz band showed a fronto‐parietal increase and that at 22–24 Hz exhibited a fronto‐central decrease. Hence, the 1–7 Hz range showed significant increases in both NREM sleep and REM sleep, with similar topography. The parallel change of NREM sleep and REM sleep EEG power is related, as confirmed by a correlational analysis, indicating that the increase in frequency of 2–7 Hz possibly subtends a state‐aspecific homeostatic response. On the contrary, sleep deprivation has opposite effects on alpha and sigma activity in both states. In particular, this analysis points to the presence of state‐specific homeostatic mechanisms for NREM sleep, limited to <2 Hz frequencies. In conclusion, REM sleep and NREM sleep seem to share some homeostatic mechanisms in response to sleep deprivation, as indicated mainly by the similar direction and topography of changes in low‐frequency activity.     

Resting EEG theta power correlates with cognitive performance in healthy older adults

We address the degree to which resting EEG bandpower is associated with cognitive performance in 73 healthy older adults (aged 56-70). Relative theta (4-6.5 Hz) power was significantly correlated with immediate and delayed verbal recall, attention, and executive function measures. Relative delta and alpha power and peak alpha frequency did not correlate with any cognitive measures. These data indicate that high resting theta power in healthy older adults is associated with better cognitive function and may be a marker of healthy neurocognitive aging. Comparison of these with previous findings suggests that two forms of theta-frequency oscillations may exist; one indicative of healthy neurocognitive function and the other, EEG/alpha slowing linked to (future) substantial cognitive decline. Future EEG investigations of cognitive aging or decline should analyze both relative theta power and degree of EEG/alpha slowing so as not to confound these.     

Usual sleep duration and cognitive function in older adults in Spain

The few studies that have examined the association between usual sleep duration and cognitive function have shown conflicting results. This cross‐sectional study examined the association between sleep duration and cognitive function among 3212 people, representative of the non‐institutionalized population aged 60 years and over in Spain. Sleep duration was self‐reported, and cognitive function was measured with the Mini‐Examen Cognoscitivo (MEC), a version of the Mini‐Mental State Examination that has been validated in Spain. Linear regression, with adjustment for the main confounders, was used to obtain mean differences in the MEC between the categories of sleep duration (≤5, 6, 7, 8, 9, 10, ≥11 h day^?1). The MEC score decreased progressively (became worse) across sleep categories from 7 to ≥11 h (P for linear trend <0.001). People who slept for ≥11 h had a significantly lower MEC score than those who slept for 7 h (mean difference ?1.48; 95% confidence interval ?2.12 to ?0.85). This difference in the MEC was similar to that observed for a 10‐year increase in age. The results did not vary significantly by sex (P for interaction >0.05). No association was observed between short sleep duration (<7 h) and cognitive function. We conclude that long sleep duration is associated with poorer cognitive function in older adults from the general population.     

Dynamic changes in quantitative electroencephalogram during continuous performance test in children with attention-deficit/hyperactivity disorder

To establish whether dynamic EEG changes in children with attention-deficit/hyperactivity disorder (ADHD) differ from those observed in controls, the authors investigated the effect of the continuous performance test (CPT) on delta, theta, alpha and beta frequency bands. High-resolution electroencephalography (EEG) was recorded during eyes-open resting and CPT performance in 16 right-handed children meeting the DSM-IV criteria for ADHD and 16 age-matched controls. Significant CPT vs. eyes-open differences in EEG activities was observed in children with ADHD. In particular, switching to CPT induced an alpha power increase in children with ADHD and an alpha power decrease in controls. This may reflect a primary deficit associated with cortical hypoarousal in ADHD. These EEG results agree with behavioral findings leading the authors to suggest that dynamic changes in neural network activities are impaired in children with ADHD.