Subjective sleep assessments are correlated with EEG-related sleep measurements of the first sleep cycle in healthy young adults

This study examined whether subjective and objective sleep parameters (sleep stage, electroencephalography [EEG] power, heart rate variability) are related to the progression of sleep cycles using differences in the variables between two nights. We hypothesized that the association between night-to-night differences between subjective and objective sleep variables reflect the difference in objective sleep variables in the first sleep cycle. Seventy-seven healthy adults (23.8 ± 2.2 years; 41 females) participated in polysomnographic recordings on two consecutive nights. To extract the variables that represent the difference between the nights, the sleep parameters of Night 1 were subtracted from those of Night 2. Spearman's rho was used to assess correlations between subjective sleep assessments and objective sleep parameters, with false discovery rate correction for multiple comparisons. Subjective sleep assessments were significantly correlated with whole-night sleep architecture and quantitative EEG activity, but not with heart rate variability during the night. Among sleep cycles, subjective sleep parameters were correlated with the objective sleep parameters in the first sleep cycle ("Ease of falling asleep" vs. waking after sleep onset [r = - 0.382], "Depth of sleep" vs. EEG theta power [r = 0.404], "Quality of sleep" vs. the percentage of stage N3 [r = 0.412] and EEG delta power [r = 0.458], all p < 0.05). These results suggest the importance of taking the difference among the nights into account when assessing subjective sleep quality. This study clarified that sleep in the first sleep cycle has a dominant influence on subjective sleep assessments.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41105-022-00437-x.

Non-REM sleep in major depressive disorder

Disturbed sleep is a key symptom in major depressive disorder (MDD). REM sleep alterations are well described in the current literature, but little is known about non-REM sleep alterations. Additionally, sleep disturbances relate to a variety of cognitive symptoms in MDD, but which features of non-REM sleep EEG contribute to this, remains unknown. We comprehensively analyzed non-REM sleep EEG features in two central channels in three independently collected datasets (N = 284 recordings of 216 participants). This exploratory and descriptive study included MDD patients with a broad age range, varying duration and severity of depression, unmedicated or medicated, age- and gender-matched to healthy controls. We explored changes in sleep architecture including sleep stages and cycles, spectral power, sleep spindles, slow waves (SW), and SW-spindle coupling. Next, we analyzed the association of these sleep features with acute measures of depression severity and overnight consolidation of procedural memory. Overall, no major systematic alterations in non-REM sleep architecture were found in patients compared to controls. For the microstructure of non-REM sleep, we observed a higher spindle amplitude in unmedicated patients compared to controls, and after the start of antidepressant medication longer SWs with lower amplitude and a more dispersed SW-spindle coupling. In addition, long-term, but not short-term medication seemed to lower spindle density. Overnight procedural memory consolidation was impaired in medicated patients and associated with lower sleep spindle density. Our results suggest that alterations of non-REM sleep EEG in MDD might be more subtle than previously reported. We discuss these findings in the context of antidepressant medication intake and age.

Sleep cycle in children with severe acute bronchopneumonia during mechanical ventilation at different depths of sedation

BACKGROUND

To investigate the characteristics of sleep cycle in children with severe acute bronchopneumonia treated with invasive mechanical ventilation at different sedation depths.

METHODS

We included 35 pediatric patients with severe acute bronchopneumonia treated using mechanical ventilation in Pediatric Intensive Care Unit of Shengjing Hospital of China Medical University. They were divided into deep sedation group (n = 21; ramsay score 5-6) and light sedation group (n = 14; ramsay score3-4) based on sedation depth achieved during mechanical ventilation. Long-term video electroencephalography (EEG) monitoring was performed within the first 24 h after starting mechanical ventilation and after weaning from mechanical ventilation and discontinuing sedatives and analgesics. The results were analyzed and compared with those of normal children to analyze changes in sleep cycle characteristics at different sedation depths and mechanical ventilation stages.

RESULTS

There were 29 cases altered sleep architecture. The deep sedation group had a significantly higher incidence of sleep architecture altered, total sleep duration, and non-rapid eye movement sleep-1 (NREM-1) loss incidence than the light sedation group. Moreover, the deep sedation group had a significantly lower awakening number and rapid eye movement sleep (REM) percentage than the light sedation group. The sleep cycle returned to normal in 27 (77%) patients without NREM-1 or REM sleep loss.

CONCLUSIONS

Deep sedation during mechanical ventilation allows longer total sleep duration, fewer awakenings, and an increased deep sleep proportion, but sleep architecture is severely altered. After weaning from mechanical ventilation and sedative discontinuation, lightly sedated children exhibit better sleep recovery.

Sex-specific association of the lunar cycle with sleep

Using one-night sleep recordings from 852 subjects all living in Uppsala, Sweden, the present study represents one of the largest polysomnography investigations into the association of the 29.53-day long lunar cycle with sleep among men and women and across a wide age range (22-81 years). Following the day after the new moon until the day of the full moon (also named the waxing period), the moon's illumination increases, and the timing of the meridian of the moon is gradually shifted from noontime toward midnight. In contrast, from the day after the full moon until the day of the new moon (also named the waning period), the moon's illumination decreases, and the timing of the meridian of the moon is gradually shifted from early night hours toward noontime. Thus, we focused on the contrast between the waxing and waning periods. Sleep duration was shorter on nights during the waxing period as compared to waning period (P < 0.001). In addition, a significant interaction effect of participants' sex with the lunar period on sleep was noted (P < 0.05). Men, but not women, exhibited lower sleep efficiency (P < 0.001 and P = 0.748, respectively) and were longer awake after sleep onset (P = 0.010 and P = 0.890, respectively) on nights during the waxing period. All associations were robust to adjustment for confounders (including regular sleep disturbances). Our findings suggest that the effects of the lunar cycle on human sleep are more pronounced among men. Based on the cross-sectional design of the study, no firm conclusions can be drawn on the causality of the relations.

Association of short-term exposure to air pollution with depression in patients with sleep-related breathing disorders

Air pollution is associated with sleep-related breathing disorders; however, the effects of air pollution on depression in patients with SRBDs remain unclear. A cross-sectional study was conducted to collect polysomnographic (PSG) data and Beck Depression Inventory-IA (BDI-IA) responses from 568 subjects with SRDBs in a sleep center in 2015 to 2017. Exposure to air pollution, including particulate matter with an aerodynamic diameter of ≤10 μm (PM₁₀), particulate matter with an aerodynamic diameter of ≤2.5 μm (PM_2.5), nitrogen (NO₂), sulfur dioxide (SO₂), carbon monoxide (CO) and ozone (O₃), in 1-month averages was collected. Associations of air pollution with the respiratory disturbance index (RDI), oxygen desaturation index (ODI), arousal index (ARI), sleep architecture, and BDI-IA were examined. We observed that interquartile range (IQR) increases in 1-month PM_2.5, PM₁₀, and NO₂ levels were respectively associated with 4.1/hour (h) (95% confidence interval (CI): 1.7/h to 6.4/h), 3.7/h (95% CI: 1.4/h to 6.0/h) and 1.9/h (95% CI: 0.1/h to 3.7/h) increases in the ARI. For sleep architecture, IQR increases in 1-month PM_2.5 and CO levels were respectively associated with a 6.2% (95% CI: 6.1% to 6.3%) increase in non-rapid eye movement sleep 1 (N1) and a 2.0% (95% CI: -3.8% to -0.1%) decrease in non-rapid eye movement sleep 2 (N2). For depression, an IQR change in the 1-month CO was associated a moderate/severe depressive status according to the BDI-IA (odds ratio, OR: 2.981, p < 0.05; 95% CI: 1.032 to 8.611). Short-term exposure to air pollution increased the risk of arousal and light sleep as well as depression in patients with SRBDs. The results suggest that SRBD patients could be a population at risk for depression due to short-term exposure to air pollution.

Question what is "known"

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We can “know” good data as true, but we cannot accept as fact interpretations of those data.

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Example: the assumption that both NREM and REM sleep are functional responses to prior wake,

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And, their cycling is controlled by a fixed period oscillator.

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Further research shows NREM and REM sleep are in a homeostatic relationship.

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Questioning interpretations can lead to valuable new research.

Characteristics of sleep architecture in autism spectrum disorders: A meta-analysis based on polysomnographic research

Eleven parameters recorded by polysomnography were used to evaluate the differences in sleep structure between individuals with autism spectrum disorders (ASDs) and typically developed individuals (TDs). Four databases (PubMed, Web of Science, Cochrane Library, and China National Knowledge Infrastructure (CNKI)) were searched for potentially relevant literature published before July 14, 2019. Data extraction was performed by two independent assessors. The Cohen's d effect sizes and their 95% confidence intervals (CIs) were calculated to assess the effectiveness with the random-effects model. The heterogeneity was estimated by Cochran's Q test. The research yielded 14 case-control studies, 11 of which were included in this meta-analysis. Synthesis of the differences in 11 sleep parameters between individuals with ASDs and TDs demonstrated the pooled effect size of Cohen'd was -0.52 (95% CI: (-0.97, -0.08)) for total sleep time (TST), -0.69 (95% CI: (-1.27, -0.11)) for sleep efficiency (SE%) and 0.93 (95% CI: (0.37, 1.48)) for stage 1 sleep (S1%), respectively. Our findings suggested that compared with TDs, individuals with ASDs tend to have a decreased TST and SE% and an increased S1%. Differences of characteristics of sleep architecture in other sleep parameters between individuals with ASDs and TDs were not found in this study.

Behavioral-state development and sleep-state differentiation during early ontogenesis

Sleep is a key process in neurodevelopment and essential for the maturation of fundamental brain functions. Premature birth can disturb the initial steps of sleep maturation, which may contribute to the impairment of neurodevelopment. It is thus fundamental to understand the maturation of the various sleep states and the quality of cerebral function in each vigilance state, as well as the development of sleep cyclicity, in at-risk neonatal infants, particularly those born premature. The objective of this review is to provide a precise description of sleep states and cycles and their rhythmic organization in premature and term newborns according to their gestational age. Technical aspects of polysomnography, which requires a high level of expertise in neonates, are also described. Principles of the visual interpretation of polysomnography, including the simultaneous analysis of behavioral (spontaneous motricity and eye movements), polysomnographic parameters (electro-oculogram, electrocardiogram, respiration), and electroencephalography patterns are presented. The neurophysiology of sleep ontogenesis and its interaction with brain maturation are discussed, highlighting the crucial role of sleep states and their duration in premature newborns. In particular, the involvement of myoclonic twitches in functional connectivity in sensorimotor development is discussed. Indeed, sleep quality, determined by combined polysomnographic parameters, reflects either normal or pathological developmental processes during the neonatal period. The fundamental place of neurophysiological explorations in the early detection of sleep disorders is discussed, as well as their potential consequences on neurodevelopmental care to improve the prevention of neurodevelopmental impairment.