Elevated beta activity in the nighttime sleep and multiple sleep latency electroencephalograms of chronic insomnia patients

EEG spectral analysis of nighttime sleep and daytime MSLTs and neurocognitive evaluations in subjects with co-morbid insomnia and OSA

BACKGROUND

Chronic insomnia and obstructive sleep apnea commonly co-occur. Few studies have explored the neurophysiological and neurocognitive characteristics of COMISA, which could help guide improving treatment diagnostic tools and determining novel therapeutic targets. This study aims to explore the neurophysiological and neurocognitive characteristics of COMISA using electroencephalographic (EEG) spectral analysis and subjective and objective neurocognitive measurements.

METHODS

Participants were from our community recruited OSA-insomnia-COMISA cohort with 206 included for our current analysis including 74 chronic insomniacs (CIs), 55 OSA patients and 77 COMISA patients. Standard polysomnography (PSG) and multiple sleep latency tests (MSLTs) were recorded and used to obtain relative EEG spectral power in each sleep stage during PSG and each session during MSLTs. A series of subjective and objective neurocognitive tests were conducted to evaluate executive function, attention, retrospective and prospective memory and meta-cognition.

RESULTS

In PSG and MSLTs, COMISA patients showed combined EEG power characteristics of both CIs and OSA. Specifically, COMISA patients exhibited similar EEG spectral characteristics to CIs, with decreased delta and increased alpha and beta power in NREM sleep stages, and increased beta power in REM and MSLTs. Similar to the EEG spectral power profile of OSA, COMISA patients showed increased delta power in REM and MSLTs. Compared to OSA patients, COMISA patients exhibited worse subjectively measured attention and meta-cognition related to negative beliefs about uncontrollability and danger of worry (NEG), which were positively associated with ISI scores.

CONCLUSIONS

The EEG spectral power characteristics of COMISA patients in overnight PSG and daytime MSLT appear to be the manifestation of elements of both CIs and OSA. However, the neurocognitive features of COMISA patients in subjectively measured attention and NEG meta-cognition were primarily affected by chronic insomnia.

Sleep alterations in major depressive disorder and insomnia disorder: A network meta-analysis of polysomnographic studies

Major depressive disorder (MDD) and Insomnia disorder (ID) are characterized by sleep alterations. To define their polysomnographic profiles, we conducted a Network Meta-Analysis comparing MDD and ID patients versus healthy controls (HCs). The literature search, conducted from 2008 up to January 2023 and following PRISMA guidelines, covered PubMed, Web of Science, Scopus, and Embase databases. We addressed publication bias using funnel plot asymmetry inspection and Egger's test, evaluated statistical heterogeneity with I2, and local and global inconsistencies with the separate indirect from direct evidence method and Q between designs, respectively. Pairwise meta-analyses employed a fixed-effects model, while network analysis utilized a random-effect approach. We evaluated 86 ID and 17 MDD studies, comparing sleep parameters for 636 MDDs versus 491 HCs, and 3661 IDs versus 2792 HCs. The network meta-analysis reported that patients with MDD have greater rapid eye movement (REM) sleep duration and REMs density, and lower REM sleep latency compared to IDs. ID patients instead exhibited lower total sleep time and time in bed, and greater wake after sleep onset and non-REM sleep stage 3 than MDD patients. This work emphasized sleep depth and continuity alterations in both MDD and ID, with major involvement of REM sleep in MDD.

Sleep Loss and Substance Use Disorders: An Issue from Adolescents to Adults

Unsatisfactory sleep is a worldwide concern, as evidenced by the high prevalence of insomnia symptoms and diagnosis in the general population, and an issue that has also risen among adolescents. These circumstances are a cause of worry due to, among other factors, the observed bidirectional association of sleep disturbances and the risk of substance use disorder development. In this regard, across the globe, several reports indicate that substance consumption is at an all-time high, with alcohol, nicotine, and cannabis leading the charts. Additionally, the age of onset has dropped, with reports suggesting that first contact is usually during adolescence. Although the nature of the link between poor sleep and substance use disorder development is still not fully understood, it is possible that an overactive orexinergic system could play a role, as it has been observed that treatment with orexinergic antagonists improves insomnia symptoms and that postmortem studies show an increase in orexin immunoreactive neurons in sections obtained from habitual opioid consumers. We further argue that it is during adolescence that this maladaptive loop can be established, priming for the development of substance use disorders.

Hyperarousal features in the sleep architecture of individuals with and without insomnia

Sleep architecture encodes relevant information on the structure of sleep and has been used to assess hyperarousal in insomnia. This study investigated whether polysomnography-derived sleep architecture displays signs of hyperarousal in individuals with insomnia compared with individuals without insomnia. Data from Phase 3 clinical trials, private clinics and a cohort study were analysed. A comprehensive set of sleep architecture features previously associated with hyperarousal were retrospectively analysed focusing on sleep-wake transition probabilities, electroencephalographic spectra and sleep spindles, and enriched with a novel machine learning algorithm called the Wake Electroencephalographic Similarity Index. This analysis included 1710 individuals with insomnia and 1455 individuals without insomnia. Results indicate that individuals with insomnia had a higher likelihood of waking from all sleep stages, and showed increased relative alpha during Wake and N1 sleep and increased theta power during Wake when compared with individuals without insomnia. Relative delta power was decreased and Wake Electroencephalographic Similarity Index scores were elevated across all sleep stages except N3, suggesting more wake-like activity during these stages in individuals with insomnia. Additionally, sleep spindle density was decreased, and spindle dispersion was increased in individuals with insomnia. These findings suggest that insomnia is characterized by a dysfunction in sleep quality with a continuous hyperarousal, evidenced by changes in sleep-wake architecture.

The influence of transcranial alternating current stimulation on EEG spectral power during subsequent sleep: A randomized crossover study

OBJECTIVE

To evaluate the instant impact of transcranial alternating current stimulation (tACS) on sleep brain oscillations.

METHODS

Thirty-six healthy subjects were randomly assigned to receive tACS and sham stimulation in a crossover design separated by a one-week washout period. After stimulation, a 2-h nap polysomnography (PSG) was performed to obtain Electroencephalogram (EEG) data and objective sleep variables, and self-reported subjective sleep parameters were collected at the end of the nap. EEG spectral analyses were conducted on the EEG data to obtain the absolute and relative power for each sleep stage during the nap. The associations between power values and objective and subjective measurements were analyzed using Spearman or Pearson correlation coefficients.

RESULTS

The tACS group presented higher power in slow wave activity (SWA) and delta frequency bands and lower alpha, sigma and beta power values compared to the sham group during the N2 and N3 sleep stages. SWA and delta power were positively associated with sleep duration and sleep efficiency relevant parameters; while alpha, sigma and beta power were positively associated with prolonged sleep latency and wakefulness related variables. PSG, self-reported and sleep diary measured objective and subjective sleep parameters were comparable between the tACS and the sham groups.

CONCLUSION

Our results support that tACS could promote sleep depth in microstructure of sleep EEG, manifesting as an increase in EEG spectral power in low frequency bands and a decrease in high frequency bands. The registration number of this study is ChiCTR2200063729.

Lateralized differences in power spectra across different frequency bands during NREM sleep in patients with primary insomnia

Objective

To compare the electroencephalogram power spectrum of patients with primary insomnia and good sleep controls in multiple brain areas and different frequency bands during non-rapid eye movement sleep.

Methods

48 primary insomnias and 30 age-and gender-matched good sleep controls were recorded overnight with polysomnography. Power spectral analysis was performed in six brain areas (F3, F4, C3, C4, O1 and O2) and across seven frequency bands (delta, sigma, alpha, theta, beta1, beta2, and gamma) during non-rapid eye movement sleep between primary insomnias and good sleep controls.

Results

In primary insomnias, there were significant differences in frequency bands and areas. Compared to good sleep controls, delta power was lower in primary insomnias, while beta1, beta2, and gamma were higher. Beta2 power was substantially higher in all areas, sigma power was significantly higher on the right side, and gamma power was considerably higher on the left side in primary insomnias. The Beta1 power was positively correlated the number of awakenings (r = 0.3291, p = 0.02) in primary insomnias on the right side.

Conclusion

This study marked the first specialized comparison of power spectral analysis during non-rapid eye movement sleep in different areas and across different frequency bands. The result suggested that primary insomnias had reduced deep sleep (lower delta power) and hyperarousal state (higher beta 2 power). Primary insomnia was associated with significant fragmented sleep, and an increase in beta1 power was related to the number of awakenings.

Significance

These findings revealed the hemispheric lateralization characteristics of power spectral disturbances during non-rapid eye movement sleep in primary insomnias and provided valuable insights for selecting electrode placements in future power spectral analyses of primary insomnias.

Insomnia disorder is associated with 24-hour cortical hyperarousal

OBJECTIVE

Cortical hyperarousal has been proposed as a primary underlying mechanism for insomnia disorder. However, most evidence comes from nighttime sleep and whether patients with insomnia disorder have cortical hyperarousal through the 24-h sleep/wake cycle is not resolved.

METHODS

We included 49 patients with insomnia disorder and 49 age-and sex-matched normal sleepers. All participants underwent an over-night polysomnography followed by a Multiple Sleep Latency Test during daytime. Nighttime and daytime delta, theta, alpha, sigma and beta relative power at central electroencephalogram derivations during wakefulness and non-rapid eye movement (NREM) sleep were calculated. Insomnia disorder was defined based on the International Classification of Sleep Disorders Third Edition criteria. Insomnia with objective short sleep duration was defined as patients with insomnia who slept <7 h based on nighttime polysomnography recording.

RESULTS

Compared to normal sleepers, patients with insomnia disorder had significantly higher nighttime (P = 0.040) and daytime (P = 0.021) relative electroencephalogram power in beta during NREM sleep and marginally significantly lower relative electroencephalogram power in theta (P = 0.060) during nighttime wakefulness. Furthermore, linear trend association was observed across normal sleepers, and patients with insomnia who slept ≥7 h and insomnia who slept <7 h in relative electroencephalogram power in beta during nighttime and daytime NREM sleep, and relative electroencephalogram power in theta during nighttime wakefulness (all P for trend <0.05).

CONCLUSION

Increased high-frequency electroencephalogram power during nighttime and daytime sleep suggests that insomnia is a disorder of 24-h cortical hyperarousal. Decreasing both nighttime and daytime cortical arousal levels should be our therapeutic target for insomnia.

Challenging subjective excessive daytime sleepiness as an insomnia symptom: a retrospective study

Diagnostic manuals describe insomnia disorder (ID) characterised by fatigue and sleepiness as diurnal consequences of nocturnal symptoms. However, patients with ID do not frequently report sleepiness in the clinical setting. The present study aimed to investigate subjective sleepiness in ID measured through the Epworth Sleepiness Scale (ESS) and its independence towards daytime functioning and fatigue, and to evaluate cognitive behavioural therapy for insomnia (CBT-I) improvement in daytime consequences and their relationship to sleepiness and fatigue. We retrospectively collected the ESS evaluation in a large sample of 105 healthy controls (HCs), 671 patients with ID, and 602 patients with sleep disorders characterised by excessive daytime sleepiness (EDS). Moreover, we conducted a pre-post evaluation of the ESS in a sub-sample of patients with ID who underwent CBT-I. Component 2 of the Insomnia Severity Index and Profile of Mood States-Fatigue Inertia Scale was used to evaluate daytime functioning and fatigue. Patients with ID reported ESS levels comparable to that observed in HCs and significantly lower than the EDS group. No significant correlation arose between ESS and the diurnal impact of the disorder, suggesting the independence between daytime functioning and sleepiness in ID. Contrarily, insomnia severity and diurnal impact significantly correlated with fatigue. Data showed a statistically significant increase in sleepiness after CBT-I, despite significantly improving daytime consequences and fatigue. Although diagnostic manuals report sleepiness and fatigue as daytime consequences of sleep symptoms in patients with ID, these retrospective data indicate a dissociation between these entities. This evidence aligns with the core feature of ID: the hyperarousal status that pervades patients also during wakefulness.

Prevalence and Associated Risk Factors of Insomnia Among Adults in Riyadh, Saudi Arabia

Background Insomnia is a common sleep disorder with significant effects on physical and mental health. This study aimed to document the prevalence of insomnia and its associated risk factors among adults in Riyadh, Saudi Arabia. Materials and methods A cross-sectional study was conducted in Riyadh using the Sleep Condition Indicator Questionnaire (SCIQ). Data were collected from 548 participants. The inclusion criteria encompassed adults aged 18 and above living in Riyadh, Saudi Arabia. Information on sociodemographic characteristics, medical history, and sleep patterns was gathered through a translated eight-item SCIQ (score ≤16=insomnia). Statistical analysis involved descriptive and inferential statistics using IBM SPSS Statistics for Windows, Version 27.0 (Released 2020; IBM Corp., Armonk, New York, United States). Results The findings revealed a significant prevalence of insomnia, affecting 219 individuals (40%). Insomnia was significantly associated with the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria, including difficulty initiating or maintaining sleep, frequency of sleep disturbances, significant distress, and duration of sleep disturbances (p<0.001 for each). The highest prevalence of insomnia was observed in the 40-60-year age group (n=91, 45.7%, p=0.014), among smokers (n=27, 60%, p=0.0063), and among obese individuals (n=20, 54.1%, p=0.035). Additionally, insomnia was strongly associated with anxiety (n=49, 66.2%, p<0.001), depression (n=27, 54%, p=0.033), and hypertension (n=24, 58.5%, p=0.011). Conclusion This study highlighted the high prevalence of insomnia among adults in Riyadh, particularly among older adults, smokers, and those with chronic health conditions. These findings underscore the need for targeted interventions to address insomnia and its associated risk factors. Future research should focus on longitudinal studies to establish causal relationships and explore the impacts of lifestyle and genetic factors on insomnia.

High stability of EEG spectral power across polysomnography and multiple sleep latency tests in good sleepers and chronic insomniacs

To assess the stability of electroencephalographic (EEG) spectral features across overnight polysomnography (PSG) and daytime multiple sleep latency tests (MSLTs) in chronic insomniacs (CIs) and normal controls (NCs). A total of 20 NCs and 22 CIs underwent standard PSG and MSLTs. Spectral analyses were performed on EEG data from PSG and MSLTs and absolute and relative power in central, frontal and occipital channels were obtained for wake (W) and non-rapid eye movement sleep stage 1 and 2 (N1, N2). Intraclass correlation coefficients (ICCs) were used to assess the stability of EEG spectral power across PSG and MSLTs for W, N1 and N2. The absolute power of all frequency bands except delta exhibited high stability across PSG and MSLTs in both NCs and CIs (ICCs ranged from 0.430 to 0.978). Although delta absolute power was stable in NCs during N1 and N2 stages (ICCs ranged from 0.571 to 0.835), it tended to be less stable in CIs during W and sleep stages (ICCs ranged from 0.042 to 0.807). We also observed lower stability of relative power compared to absolute power though the majority of relative power outcomes maintained high stability in both groups (ICCs in relative power ranged from 0.044 to 0.962). Most EEG spectral bandwidths across PSG and MSLT in W, N1 and N2 show high stability in good sleepers and chronic insomniacs. EEG signals from either an overnight PSG or a daytime MSLT may be useful for reliably exploring EEG spectral features during wakefulness or sleep.

Neurophysiological Parameters Influencing Sleep-Wake Discrepancy in Insomnia Disorder: A Preliminary Analysis on Alpha Rhythm during Sleep Onset

Sleep state misperception (SSM) is a common issue in insomnia disorder (ID), causing a discrepancy between objective and subjective sleep/wake time estimation and increased daytime impairments. In this context, the hyperarousal theory assumes that sustained central nervous system activation contributes to the SSM. This study investigates factors influencing SSM during sleep latency (SL) and total sleep time (TST). Objective polysomnographic sleep variables (the alpha density index, latency-to-sleep stages and the first K-complex, and Rapid Eye Movement (REM) arousal density) and subjective sleep indices, taken from sleep diaries, were analyzed in 16 ID patients. Correlation analyses revealed a positive association between the degree of SL misperception (SLm) and the percentage of epochs that contained a visually scored stereotyped alpha rhythm during objective SL. A regression analysis showed that the REM arousal density and alpha density index significantly predicted TST misperception (TSTm). Furthermore, the degree of SLm was associated with an increased probability of transitioning from stage 1 of non-REM sleep to wakefulness during subjective SL. These findings support the role of hyperarousal in SSM and highlight the importance of alpha activity in unravelling the heterogeneous underpinnings of SSM.