Paradoxical insomnia and subjective-objective sleep discrepancy: A review

Shorter sleep duration is associated with lower GABA levels in the anterior cingulate cortex

BACKGROUND

Alterations in the levels of gamma-aminobutyric acid (GABA) and glutamate + glutamine (Glx), which are major inhibitory and excitatory neurotransmitters, respectively, are frequently associated with insomnia. Previous reports also suggested the involvement of the anterior cingulate cortex (ACC) and medial prefrontal cortex (mPFC) in insomnia and shorter sleep duration. In the current study, we investigated whether the GABA and Glx levels were altered in the ACC/mPFC in subclinical insomnia while focusing on the sleep duration.

METHODS

We examined levels of GABA and Glx in the ACC/mPFC of the brain with magnetic resonance spectroscopy in 166 individuals with subjective sleep complaints but without a diagnosis of insomnia. Participants were divided into two groups according to sleep duration (≥6 h/night: n = 79 vs. < 6 h/night: n = 74), which was measured using a wrist-worn actigraphy. Working memory function and overall subjective sleep quality were assessed with a computerized neuropsychological test and self-report questionnaire, respectively.

RESULTS

GABA levels in the ACC/mPFC were lower in the shorter sleep duration group relative to the longer sleep duration group (t = -2.21, p = 0.03). Glx levels did not differ between the two groups (t = -0.20, p = 0.84). Lower GABA levels were associated with lower spatial working memory performance in the shorter sleep duration group (β = -0.21, p = 0.03), but not the longer sleep duration group (β = 0.04, p = 0.72).

CONCLUSION

Shorter sleep duration was associated with lower GABA levels in the ACC/mPFC. These findings may provide insight into the underlying mechanisms of impaired working memory function related to insomnia and sleep loss.

Sleep continuity, stability and organization in good and bad sleepers

The relationship between objective and subjective sleep quality is still debated. Here, we investigate differences in objective sleep parameters in habitual subjective good sleepers and bad sleepers with the aim of evaluating sleep continuity, stability and organization as possible determinants of subjective sleep quality. In total, 38 subjects (good sleepers, N = 18; bad sleepers, N = 20) underwent two nights of sleep recording. Traditional sleep parameters displayed no between-groups differences. Conversely, bad sleepers showed lower sleep continuity (awakenings frequency), stability (e.g. arousals and state transitions frequency) and organization (e.g. number of sleep cycles and time spent in cycles). Our findings point to the involvement of these measures in determining habitual sleep quality perception and suggest the possibility to include them in standard sleep assessments.

Brain Structural and Functional Alterations Specific to Low Sleep Efficiency in Major Depressive Disorder

Background

Sleep disturbance is common in patients with major depressive disorder (MDD), but the exploration of its neural underpinnings is limited by subjective sleep measurement and single-modality neuroimaging analyses.

Methods

Ninety six patients with MDD underwent polysomnography examinations and multi-modal magnetic resonance imaging (MRI) scans. According to sleep efficiency, patients were subdivided into well-matched normal sleep efficiency (NSE, N = 42; 14 men; aged 43 ± 10 years) and low sleep efficiency (LSE, N = 54; 23 men; aged 45 ± 12 years) groups. Inter-group differences in brain structure and function were examined by applying voxel-based morphometry (VBM), regional homogeneity (ReHo) and functional connectivity strength (FCS), and tract-based spatial statistics (TBSS) approaches to structural, functional, and diffusion MRI data, respectively.

Results

There was no significant difference in gray matter volume (GMV) between the NSE and LSE groups. Compared with the NSE group, the LSE group showed increased axial diffusivity in the left superior and posterior corona radiata, and left posterior limb and retrolenticular part of internal capsule. In addition, the LSE group exhibited decreased ReHo in the bilateral lingual gyri and right postcentral gyrus yet increased FCS in the left angular gyrus relative to the NSE group. Moreover, validation analyses revealed that these results remained after adjusting for the medication effect.

Conclusion

Our data indicate that preserved gray matter morphology, impaired white matter integrity, and decreased local synchronization degree yet increased FCS are specific to low SE in MDD patients. These findings of disassociation between structural and functional alterations might provide insights into the neural mechanisms of sleep disturbance in depression.

Focusing on insomnia symptoms to better understand depression: A STAR*D report

BACKGROUND

Disturbed sleep is a core symptom of major depressive disorder (MDD), with nearly 90% of those with MDD reporting disturbed sleep. However, combining insomnia and hypersomnia into a single diagnostic domain ignores distinct biological differences between those symptom presentations. To better understand depression it may be necessary to explore these symptoms independently, beginning with the more prevalent insomnia.

METHOD

The present study evaluated global insomnia symptom severity in a broad sample of MDD outpatients from the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) trial, excluding patients who reported hypersomnia symptoms. The three insomnia-related symptoms from the 16-item Quick Inventory of Depressive Symptomatology- clinician rated (QIDS-C) were combined to create a global insomnia score to classify baseline insomnia severity. A modified depression severity score was then used to assess depression severity (mQIDS-C), excluding sleep-related items.

RESULTS

A repeated measures ANCOVA revealed a significant improvement in insomnia score over the acute phase treatment (F = 33.1, d.f. = 6, 9897, p < 0.0001). Improvement in insomnia score over the acute phase treatment remained statistically significant even after controlling for change in depression severity (p = 0.0004). Participants with one point higher insomnia score at baseline were significantly less likely to remit at study exit (odds ratio = 0.88, 95% confidence interval = 0.85, 0.92, p < 0.0001) even after controlling for baseline depression severity.

LIMITATIONS

Objective confirmation of sleep profiles was not available.

CONCLUSION

Greater severity of insomnia reduces likelihood of MDD remission, and insomnia symptoms improved independent of depression remission.

Healthy Sleepers Can Worsen Their Sleep by Wanting to Do so: The Effects of Intention on Objective and Subjective Sleep Parameters

PURPOSE

Sleep is regulated by homeostatic and circadian factors. In addition, psychological factors have a strong modulatory impact on our sleep, but the exact underlying mechanisms are still largely unknown. Here, we examined the role of intentions on subjective and objective sleep parameters. Young healthy sleepers were instructed to voluntarily either worsen or improve their sleep. We predicted that participants would be capable of worsening, but not improving, their sleep compared to a regular sleep condition. In addition, we predicted that the instruction to alter sleep would lead to a higher discrepancy between subjective and objective sleep variables.

PARTICIPANTS AND METHODS

Twenty-two healthy students participated in one adaptation and three experimental nights. Polysomnography and subjective sleep parameters were measured during all four nights. Participants were instructed to sleep regularly ("neutral"), better ("good") or worse ("bad") than normal, in a counterbalanced order.

RESULTS

The instruction to sleep "bad" increased objective sleep onset latency and the number of awakings during the night. The effects were stronger on subjective sleep variables, resulting in a higher sleep misperception in the "bad" condition as compared to the other two conditions. The instruction to sleep "good" did not improve sleep nor did it affect sleep misperception.

CONCLUSION

We conclude that intention is sufficient to impair (but not improve) subjective and objective sleep quality and to increase sleep misperception in healthy young sleepers. Our results have important implications for the understanding of the impact of psychological factors on our sleep.

Unstable wakefulness during resting-state fMRI and its associations with network connectivity and affective psychopathology in young adults

BACKGROUND

Drifts between wakefulness and sleep are common during resting state functional MRI (rsfMRI). Among healthy adults, within-scanner sleep can impact functional connectivity of default mode (DMN), task-positive (TPN), and thalamo-cortical networks. Because dysfunctional arousal states (i.e., sleepiness, sleep disturbance) are common in affective disorders, individuals with affective psychopathology may be more prone to unstable wakefulness during rsfMRI, hampering the estimation of clinically meaningful functional connectivity biomarkers.

METHODS

A transdiagnostic sample of 150 young adults (68 psychologically distressed; 82 psychiatrically healthy) completed rsfMRI and reported whether they experienced within-scanner sleep. Symptom scales were reduced into depression/anxiety and mania proneness dimensions using principal component analysis. We evaluated associations between within-scanner sleep, clinical status, and functional connectivity of the DMN, TPN, and thalamus.

RESULTS

Within-scanner sleep during rsfMRI was reported by 44% of participants (n = 66) but was unrelated to psychiatric diagnoses or mood symptom severity (p-values > 0.05). Across all participants, self-reported within-scanner sleep was associated with connectivity signatures akin to objectively-assessed sleep, including lower within-DMN connectivity, lower DMN-TPN anti-correlation, and altered thalamo-cortical connectivity (p < 0.05, corrected). Among participants reporting sustained wakefulness (n = 84), depression/anxiety severity positively associated with averaged DMN-TPN connectivity and mania proneness negatively associated with averaged thalamus-DMN connectivity (p-values < 0.05). Both relationships were attenuated and became non-significant when participants reporting within-scanner sleep were included (p-values > 0.05).

LIMITATIONS

Subjective report of within-scanner sleep.

CONCLUSIONS

Findings implicate within-scanner sleep as a source of variance in network connectivity; careful monitoring and correction for within-scanner sleep may enhance our ability to characterize network signatures underlying affective psychopathology.

Moving beyond self-report data collection in the natural environment: A review of the past and future directions for ambulatory assessment in eating disorders

OBJECTIVE

In recent years, ecological momentary assessment (EMA) has been used to repeatedly assess eating disorder (ED) symptoms in naturalistic settings, which has allowed for increased understanding of temporal processes that potentiate ED behaviors. However, there remain notable limitations of self-report EMA, and with the rapid proliferation of technology there are ever-increasing possibilities to improve ambulatory assessment methods to further the understanding and treatment of EDs. Therefore, the purpose of this review was to (a) systematically review the studies in EDs that have utilized ambulatory assessment methods other than self-report, and (b) provide directions for future research and clinical applications.

METHOD

A systematic literature search of electronic databases was conducted, and data regarding study characteristics and methodological quality were extracted.

RESULTS

The search identified 17 studies that used ambulatory assessment methods to gather objective data, and focused primarily on autonomic functioning, physical activity, and cognitive processes in ED and control groups.

DISCUSSION

Together the literature demonstrates the promise of using a range of ecologically valid ambulatory assessment approaches in EDs, though there remains limited research that has utilized methods other than self-report (e.g., wearable sensors), particularly in recent years. Going forward, there are several technology-enhanced momentary assessment methods that have potential to improve the understanding and treatment of EDs.

Factors associated with fatigue in patients with insomnia

Although fatigue is common in insomnia, the clinical associates of fatigue in patients with insomnia are largely unknown. We aimed to investigate the clinical associates of fatigue in patients with insomnia. Patients visiting the Stanford Sleep Medicine Center completed the Insomnia Severity Index (ISI), Insomnia Symptom Questionnaire (ISQ), the Fatigue Severity Scale (FSS), the Epworth Sleepiness Scale (ESS), and the Patient Health Questionnaire (PHQ-9). Among 6367 patients, 2024 were diagnosed with insomnia (age 43.06 ± 15.19 years; 1110 women and 914 men) according to the ISI and the ISQ. Insomnia patients with severe fatigue (n = 1306) showed higher insomnia symptoms, daytime sleepiness, depression and longer habitual sleep duration than those without severe fatigue (n = 718). Higher insomnia symptoms, daytime sleepiness and depressive symptoms, and longer habitual sleep duration, independently predicted higher fatigue scores. Among insomnia patients with daytime sleepiness (ESS≥10), only habitual sleep duration and depression predicted fatigue scores. The interaction between insomnia severity and daytime sleepiness significantly predicted the severity of fatigue. Depression was a significant mediator between insomnia and fatigue. For 598 insomnia patients undergoing overnight polysomnography (PSG), no significant correlations were found between fatigue and any PSG parameters. The current study suggests that managing insomnia or depression may reduce the fatigue of insomnia patients, whereas arbitrary efforts to prolong sleep duration may worsen their fatigue.

Changes in Subjective-Objective Sleep Discrepancy Following Inpatient Cognitive Behavior Therapy for Insomnia

Discrepancy between objective and subjective sleep parameters is a frequent symptom in persons suffering from insomnia. Since it has an impairing effect on daytime well-being and neglects possible positive objective improvements, it would be useful if it was treated. Apart from hypnotics, cognitive behavior therapy (CBT-I) is the therapy of choice for chronic forms of insomnia. However, there is limited information about whether CBT-I can also improve subjective-objective sleep discrepancy. We investigated a large sample of patients showing chronic forms of insomnia regarding their subjective-objective sleep discrepancy pre and post CBT-I. Objective sleep data were obtained from 3 nights (2 baseline nights and 1 night after therapy) using polysomnography in our sleep laboratory. All 92 patients participated in a 14-day inpatient program with CBT-I including psychoeducation about subjective-objective sleep discrepancy. Repeated measures analyses showed an improvement in subjective-objective sleep discrepancy parameters after CBT-I. Those parameters were also correlated with perceived quality of sleep. We conclude that CBT-I is a useful tool to improve subjective-objective sleep discrepancy in patients showing chronic forms of insomnia.

Psychometric properties of the Kurdish version of Pittsburgh Sleep Quality Index

BACKGROUND

The Pittsburgh Sleep Quality Index (PSQI) is a standardized questionnaire that used for subjective assessment of sleep quality. It has been translated into several languages and is widely used in clinical research settings. Since there is no sleep-related scale standardized in the Kurdish language, the present study aimed to translate and validate the PSQI into Kurdish.

METHODS

First, the PSQI was successfully translated into Kurdish then back-translated into English by independent professional bilingual translators. The translated version of PSQI was tested with 230 participants, 150 healthy subjects, 40 subjects with insomnia, and 40 subjects with physical symptoms. Internal consistency was calculated by the Cronbach Alpha method using SPSS-20 software. Spearman correlation via a test-retest process was used for reliability. The General Health Questionnaire (GHQ28) was used to analyze criterion validity. The construct validity of the scale was tested by exploratory factor analysis (EFA). Factor weight was checked by confirmatory factor analysis (CFA) using LISREL software version 8.8.

RESULTS

The internal consistency and reliability for PSQI global score was acceptable (Cronbach's alpha = 0.70). The result showed a strong correlation between test and retest after six weeks (r = 0.83). Correlations between the global score and components of the PSQI with the GHQ28 were all statistically significant (r = 0.23-0.72, p < 0.05). Exploratory factor analysis revealed three factors with a significant correlation between the PSQI global score and these factors. All factor weights were above 0.40.

CONCLUSION

The results of this study support the PSQI's validity and reliability. This study offers a foundation for further studies in Kurdish populations.

Association between Healthy Dietary Patterns and Self-Reported Sleep Disturbances in Older Men: The ULSAM Study

To date, little is known about how dietary patterns may link to measures of sleep quality in older subjects, who often suffer from sleep problems. Here, we investigated, in an older male population from Sweden (n = 970; aged 71 ± 1 year), whether adherence to the Healthy Diet Indicator (HDI; based on recommendations from the World Health Organization) or the Mediterranean Diet (MD) is linked to sleep disturbances. The diet scores were calculated using a seven-day food diary, and self-reported sleep initiation or maintenance problems were assessed by questionnaires. When adjusted for potential confounders, no associations between dietary scores and sleep parameters were found. In contrast, low consumption of milk and dairy products —one of the dietary features of the MD —was associated with better subjective sleep initiation. This association was, however, not found in men with adequate reports of daily energy intake (~54% of the cohort). To summarize, our findings do not suggest that older men can mitigate perceived difficulties to fall and stay asleep by adhering to either the HDI or MD. Whether low consumption of milk and dairy products can facilitate sleep initiation must be confirmed in future studies by utilizing objective measures of sleep such as polysomnography. Finally, when investigating associations between dietary patterns and sleep, particular attention should be paid to the potential confounder of inadequate reporting of energy intake.

The paradox of paradoxical insomnia: A theoretical review towards a unifying evidence-based definition

Paradoxical insomnia is one of the most intriguing yet challenging subtypes of insomnia. Despite being recognized for a long time by the international community, it is still unclear whether this entity really exists, which are its features and boundaries. Much of the debate is fuelled by the lack of a consensus on its precise definition. To help filling some of the existing gaps, a systematic review of the literature was conducted, through which 19 different quantitative definitions were obtained. These definitions were then applied to two distinct datasets. The first consisted of 200 chronic primary insomnia patients, diagnosed according to the DSM-IV-TR criteria. The second consisted of 200 age- and sex-matched healthy persons without insomnia. For each dataset, available data from the objective sleep parameters and their subjective estimation were imported and analysed in MATLAB. Depending on the definition used, the prevalence of paradoxical insomnia ranged from 8 to 66%, while agreement between different definitions ranged from -0.19 to 0.9 (using Cohen's kappa coefficient). Based on the results garnered, necessary features for a quantitative definition of paradoxical insomnia were identified. Several open questions remain, such as whether there is a minimum number of hours a patient should sleep to fulfill the criteria for a diagnosis of paradoxical insomnia, and whether sleep latency can be used in the definition along with total sleep time. We conclude by advocating continued study of paradoxical insomnia and sleep state misperception and by providing specific directions for future research. STATEMENT OF SIGNIFICANCE: The current understanding of paradoxical insomnia and, more broadly, of sleep state misperception, is greatly hampered by the lack of agreement on a quantitative and evidence-base measure of the discrepancy between subjective and objective sleep evaluation. The current study provides a critical analysis about the strength and the limitations of the available definitions, using both a data-driven and a theory-driven approach. The overarching goal is to motivate a rigorous discussion involving the main experts of the field, to build a consensus, and develop an evidence-based measure of sleep state misperception and/or of paradoxical insomnia.

A lack of consistent brain alterations in insomnia disorder: An activation likelihood estimation meta-analysis

Insomnia disorder is a prevalent sleep disorder, which affects about 10% of general population. However, its neural mechanisms are poorly understood. Recently, several structural and functional neuroimaging studies have been conducted in patients with insomnia disorder, but these studies have yielded diverse findings. Here, we aimed to identify consistent patterns of abnormal brain alterations in insomnia disorder by performing a quantitative coordinate-based meta-analysis. Following the preferred reporting for systematic reviews and meta-analyses statement, we searched PubMed database and used reference tracking and finally retrieved 19 eligible studies (six task-based functional magnetic resonance imaging, eight resting-state functional magnetic resonance imaging, three voxel-based morphometry, and two positron emission tomography). We extracted peak coordinates from these studies and tested for convergence using the activation likelihood estimation method. Using this method, we found no significant convergent evidence for combination of structural atrophy and functional disturbances across previous studies (p = 0.914). Inconsistencies across these studies might be related to heterogonous clinical populations, the explorative nature of these studies in combination with small sample sizes, different experimental designs, and various preprocessing and statistical approaches. Future neuroimaging studies on insomnia disorder should include larger well-characterized samples, as well as standard imaging and analysis protocols.