Sleep in patients with primary dystonia: A systematic review on the state of research and perspectives

Patients with primary dystonia, the third most prevalent movement disorder, suffer from a markedly reduced quality of life. This might, at least in part, be mediated by non-motor symptoms, including sleep disturbances. Characterising and treating sleep disturbances might provide new inroads to improve relevant patient-centred outcomes. This review evaluates the state of research on sleep in patients with dystonia and outlines an agenda for future research. A literature search was performed in July 2014 using PubMed, Medline via Ovid, PsycInfo, PsycArticles via Proquest and Embase via Ovid. Search results were screened for eligibility by two independent raters. Peer-reviewed publications reporting on sleep in patients with primary dystonia were included. Of 1445 studies identified through the search strategy, 18 met the inclusion criteria. In total, the included studies reported on 708 patients diagnosed with focal dystonia (cervical dystonia or blepharospasm), torsion dystonia, and dopa-responsive dystonia. The results indicate that at least half of the patients with focal cranial dystonia suffer from sleep disturbances, but excessive daytime sleepiness is uncommon. Sleep disturbance is associated with depressive symptoms. The frequency and duration of dystonic movements is markedly reduced during sleep. Reduced sleep quality appears to persist after treatment with botulinum toxin that successfully reduces motor symptoms. The findings are limited by a high clinical and methodological heterogeneity. Future research is needed to i) further characterize subjective and PSG sleep in patients with different types of dystonia, ii) determine the aetiology of sleep disturbances (e.g., abnormal brain function associated with dystonia, side effects of medication, psychological reasons), and iii) test whether targeted sleep interventions improve sleep and quality of life in patients with primary dystonia.

Patients with primary insomnia in the sleep laboratory: do they present with typical nights of sleep?

The validity of sleep laboratory investigations in patients with insomnia is important for researchers and clinicians. The objective of this study was to examine the first-night effect and the reverse first-night effect in patients with chronic primary insomnia compared with good sleeper controls. A retrospective comparison of a well-characterised sample of 50 patients with primary insomnia and 50 good sleeper controls was conducted with respect to 2 nights of polysomnography, and subjective sleep parameters in the sleep laboratory and the home setting. When comparing the first and second sleep laboratory night, a significant first-night effect was observed across both groups in the great majority of the investigated polysomnographic and subjective variables. However, patients with primary insomnia and good sleeper controls did not differ with respect to this effect. Regarding the comparison between the sleep laboratory nights and the home setting, unlike good sleeper controls, patients with primary insomnia reported an increased subjective sleep efficiency on both nights (in part due to a reduced bed time) and an increased subjective total sleep time on the second night. These results suggest that even the second sleep laboratory night does not necessarily provide clinicians and researchers with a representative insight into the sleep perception of patients with primary insomnia. Future studies should investigate whether these findings also hold for other patient populations.

Reduced anterior internal capsule white matter integrity in primary insomnia

Chronic insomnia is one of the most prevalent central nervous system diseases, however, its neurobiology is poorly understood. Up to now, nothing is known about the integrity of white matter tracts in insomnia patients. In this study, diffusion tensor imaging (DTI) was used in a well-characterized sample of primary insomnia (PI) patients and good sleeper controls to fill this void. Voxelwise between-group comparisons of fractional anisotropy (FA) were performed in 24 PI patients (10 males; 14 females; 42.7 ± 14.5 years) and 35 healthy good sleepers (15 males; 20 females; 40.1 ± 9.1 years) with age and sex as covariates. PI patients showed reduced FA values within the right anterior internal capsule and a trend for reduced FA values in the left anterior internal capsule. The results suggest that insomnia is associated with a reduced integrity of white matter tracts in the anterior internal capsule indicating that disturbed fronto-subcortical connectivity may be a cause or consequence of the disorder.

Fear extinction as a model for synaptic plasticity in major depressive disorder

BACKGROUND

The neuroplasticity hypothesis of major depressive disorder proposes that a dysfunction of synaptic plasticity represents a basic pathomechanism of the disorder. Animal models of depression indicate enhanced plasticity in a ventral emotional network, comprising the amygdala. Here, we investigated fear extinction learning as a non-invasive probe for amygdala-dependent synaptic plasticity in patients with major depressive disorder and healthy controls.

METHODS

Differential fear conditioning was measured in 37 inpatients with severe unipolar depression (International Classification of Diseases, 10th revision, criteria) and 40 healthy controls. The eye-blink startle response, a subcortical output signal that is modulated by local synaptic plasticity in the amygdala in fear acquisition and extinction learning, was recorded as the primary outcome parameter.

RESULTS

After robust and similar fear acquisition in both groups, patients with major depressive disorder showed significantly enhanced fear extinction learning in comparison to healthy controls, as indicated by startle responses to conditioned stimuli. The strength of extinction learning was positively correlated with the total illness duration.

CONCLUSIONS

The finding of enhanced fear extinction learning in major depressive disorder is consistent with the concept that the disorder is characterized by enhanced synaptic plasticity in the amygdala and the ventral emotional network. Clinically, the observation emphasizes the potential of successful extinction learning, the basis of exposure therapy, in anxiety-related disorders despite the frequent comorbidity of major depressive disorder.

The prediction of treatment outcomes by early maladaptive schemas and schema modes in obsessive-compulsive disorder

BACKGROUND

Higher levels of early maladaptive schemas (EMS) and schema modes according to schematherapy by Jeffrey Young are present in obsessive-compulsive disorder (OCD) compared to healthy controls. This study examines the relationship of EMS and schema modes to OC symptom severity and the predictive value of EMS and schema modes on treatment outcome in inpatients receiving Cognitive-Behavioral Therapy (CBT) with Exposure and Response Prevention (ERP). The main assumption was a negative association between the EMS of the domain 'disconnection' and dysfunctional coping and parent schema modes and the treatment outcome.

METHODS

EMS, schema modes, depression and traumatic childhood experiences were measured in 70 patients with OCD. To analyze the predictors, two regression analyses were conducted considering multiple variables, such as depression, as covariates.

RESULTS

Regression analyses demonstrated that higher scores on the EMS named failure and emotional inhibition and depressive symptom severity at pretreatment were significantly related to poor outcome and explained a high percentage of the variance in OC symptoms at posttreatment. No influence on the treatment outcome was observed for schema modes, other EMS or other covariates.

CONCLUSIONS

The results support the approach to extend the CBT with ERP treatment with therapeutic elements focusing on maladaptive schemas, particularly in non-responders.

No talking, just writing! Efficacy of an Internet-based cognitive behavioral therapy with exposure and response prevention in obsessive compulsive disorder

BACKGROUND

Many patients with obsessive-compulsive disorder (OCD) do not receive first-line treatment according to the current guidelines (cognitive behavioral therapy with exposure and response prevention, CBT with ERP) due to barriers to treatment. Internet-based therapy is designed to overcome these barriers. The present study evaluates the efficacy of an Internet-based writing therapy with therapeutic interaction based on the concept of CBT with ERP for patients with OCD.

METHODS

Thirty-four volunteers with OCD according to DSM-IV-criteria were included in the trial and randomized according to a waiting-list control design with follow-up measures at 8 weeks and 6 months. The intervention consisted of 14 sessions, either starting directly after randomization or with an 8-week delay. Main outcome measure was the change in the severity of OCD symptoms (Yale-Brown Obsessive Compulsive Scale Self-Rating, Y-BOCS SR, and Obsessive-Compulsive Inventory-Revised, OCI-R).

RESULTS

Obsessive-compulsive symptoms were significantly improved in the treatment group compared to the waiting-list control group with large effect sizes of Cohen's d = 0.82 (Y-BOCS SR) and d = 0.87 (OCI-R), using an intention-to-treat analysis. This effect remained stable at 6-month follow-up. Only 4 participants (12%) dropped out prematurely from the study. Of the 30 completers, 90% rated their condition as improved and would recommend the program to their friends.

CONCLUSIONS

Internet-based writing therapy led to a significant improvement of obsessive-compulsive symptoms. Even though replications with larger sample sizes are needed, the results support the notion that Internet-based approaches have the potential for improving the treatment situation for patients with OCD.

Insomnia disorder is associated with increased amygdala reactivity to insomnia-related stimuli

STUDY OBJECTIVES

Alterations in emotional reactivity may play a key role in the pathophysiology of insomnia disorder (ID). However, only few supporting experimental data are currently available. We evaluated in a hypothesis-driven design whether patients with ID present altered amygdale responses to emotional stimuli related and unrelated to the experience of insomnia and, because of chronic hyperarousal, less habituation of amygdala responses.

DESIGN

Case-control study.

SETTING

Departments of Psychiatry and Psychotherapy and of Radiology of the University of Freiburg Medical Center.

PARTICIPANTS

There were 22 patients with ID (15 females; 7 males; age 40.7 ± 12.6 y) and 38 healthy good sleepers (HGS, 21 females; 17 males; age 39.6 ± 8.9 y).

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

In a functional magnetic resonance imaging session, five different blocks of pictures with varying emotional arousal, valence, and content (insomnia-relatedness) were presented. Pictures were presented twice to test for habituation processes. Results showed that patients with ID, compared to HGS, presented heightened amygdala responses to insomnia-related stimuli. Moreover, habituation of amygdale responses was observed only in HGS, but not in patients with ID who showed a mixed pattern of amygdala responses to the second presentation of the stimuli.

CONCLUSIONS

The results provide evidence for an insomnia-related emotional bias in patients with ID. Cognitive behavior treatment for ID could benefit from strategies dealing with the emotional charge associated with the disorder. Further studies should clarify the role of ID with respect to habituation of amygdala responses.

The relationship between brain morphology and polysomnography in healthy good sleepers

BACKGROUND

Normal sleep continuity and architecture show remarkable inter-individual variability. Previous studies suggest that brain morphology may explain inter-individual differences in sleep variables.

METHOD

Thirty-eight healthy subjects spent two consecutive nights at the sleep laboratory with polysomnographic monitoring. Furthermore, high-resolution T1-weighted MRI datasets were acquired in all participants. EEG sleep recordings were analyzed using standard sleep staging criteria and power spectral analysis. Using the FreeSurfer software for automated segmentation, 174 variables were determined representing the volume and thickness of cortical segments and the volume of subcortical brain areas. Regression analyses were performed to examine the relationship with polysomnographic and spectral EEG power variables.

RESULTS

The analysis did not provide any support for the a-priori formulated hypotheses of an association between brain morphology and polysomnographic variables. Exploratory analyses revealed that the thickness of the left caudal anterior cingulate cortex was positively associated with EEG beta2 power (24-32 Hz) during REM sleep. The volume of the left postcentral gyrus was positively associated with periodic leg movements during sleep (PLMS).

CONCLUSIONS

The function of the anterior cingulate cortex as well as EEG beta power during REM sleep have been related to dreaming and sleep-related memory consolidation, which may explain the observed correlation. Increased volumes of the postcentral gyrus may be the result of increased sensory input associated with PLMS. However, due to the exploratory nature of the corresponding analyses, these results have to be replicated before drawing firm conclusions.

Entwicklung von 130 deutschsprachigen Compound Remote Associate (CRA)-Worträtseln zur Untersuchung kreativer Prozesse im deutschen Sprachraum

Der Compound Remote Associate (CRA) -Test stellt eine wichtige Aufgabe für die systematische Untersuchung verbal-assoziativer Prozesse als ein Korrelat für Kreativität dar, der bislang nur im englischen Sprachraum zur Verfügung stand. Der Test besteht aus Worträtseln mit jeweils drei nicht verwandten Stimuluswörtern (Triadenkonstituenten), für die ein viertes, mit allen drei Wörtern assoziiertes Wort (gemeinsames Assoziat) gefunden werden soll. Gegenstand der vorliegenden Arbeit war die Entwicklung und der Einsatz von 130 CRA-Worträtseln für den deutschen Sprachraum. Hierzu wurden zwei Gruppen von 40 Probanden 65 neu entwickelte CRA-Worträtsel für die Dauer von maximal 60 Sekunden dargeboten. Die vorliegende Arbeit stellt die Worträtsel sortiert nach aufsteigendem Schwierigkeitsgrad vor. Als Normwerte werden für vier Zeitintervalle (5 s, 15 s, 30 s und 60 s) die Anzahl der Probanden, die das Worträtsel gelöst haben (%), die mittlere Lösungszeit (s) sowie die Lösung mit Einsicht (%) angegeben. Der Datensatz ermöglicht auch in der deutschsprachigen Forschung den Einsatz einer etablierten Aufgabe zu Einsicht und Problemlösen, um das Konstrukt „Kreativität” weiter zu erschließen.

Heterogeneity of stimulus-specific response modification-an fMRI study on neuroplasticity

Long-term potentiation (LTP) is a key element of synaptic plasticity. At the macroscopic level, similar effects can be induced in the human brain using repetitive stimulation with identical stimuli. High-frequency stimulation (HFS) can increase neuronal responses whereas low-frequency stimulation may produce the opposite effect. Optimal stimulation frequencies and characteristics for inducing stimulus-specific response modification (SRM) differ substantially from those applied to brain tissue slices but have been explored in recent studies. In contrast, the individual manifestation of this effect in terms of its spatial location and extent are unclear. Using functional magnetic resonance imaging (fMRI) in 18 subjects (mean age 25.3 years), we attempted to induce LTP-like effects by HFS with checkerboard flashes at 9 Hz for 120 s. As expected, flashes induced strong activation in primary and secondary visual cortices. Contrary to our expectations, we found clusters of decreased activations induced by pattern flashes after HFS in the primary and secondary visual cortices. On the level of the individual subject, some showed significantly increased activations in the post-HFS session while the majority showed significant decreases. The locations of areas showing altered activations before and after HFS were only partly overlapping. No association between location, extent and direction of the HFS-effect was observed. The findings are unexpected in the light of existing HFS-studies, but mirror the high inter-subject variability, concerning even the directionality of the induced effects shown for other indices of LTP-like plasticity in the human brain. As this variability is not observed in LTP at the cellular level, a better understanding of LTP-like mechanisms on the macroscopic level is essential for establishing tools to quantify individual synaptic plasticity in-vivo.

Prolonged sleep under Stone Age conditions

STUDY OBJECTIVES

We report on a unique experiment designed to investigate the impact of prehistoric living conditions on sleep-wake behavior.

METHODS

A group of five healthy adults were assessed during life in a Stone Age-like settlement over two months.

RESULTS

The most notable finding was that nocturnal time in bed and estimated sleep time, as measured by actigraphy, markedly increased during the experimental period compared to the periods prior to and following the experiment. These increases were primarily driven by a phase-advance shift of sleep onset. Subjective assessments of health and functioning did not reveal any relevant changes across the study.

CONCLUSIONS

Our observations provide further evidence for the long-held belief that the absence of modern living conditions is associated with an earlier sleep phase and prolonged sleep duration.

COMMENTARY

A commentary on this article appears in this issue on page 723.

[Sleep, learning and memory: relevance for psychiatry and psychotherapy]

BACKGROUND

Sleep has been identified as a state that optimizes the consolidation of newly acquired information in the memory. Sleep disturbances might essentially contribute to memory impairment in relevant psychiatric disorders, such as major depression and schizophrenia.

METHODS

This article provides a brief review of the latest research results on sleep and its association with memory consolidation.

RESULTS AND CONCLUSION

Specific disturbances of sleep structure are associated with particular memory deficits in psychiatric patients. Effective treatment of sleep disorders should not only improve signs of sleep but should also heal associated memory impairments.

The effect of personality disorders on treatment outcomes in patients with obsessive-compulsive disorders

The effect of comorbid personality disorders (PD) on treatment outcomes in obsessive-compulsive disorder (OCD) is unclear. The authors systematically review results from investigations of therapy outcomes in adult patients with OCD and a comorbid PD. PsycINFO and MEDLINE were searched for original articles. Twenty-three studies assessing PDs through interviews were selected. Cluster A PDs, particularly schizotypal PD, narcissistic PD, and the presence of two or more comorbid PDs, were associated with poorer treatment outcomes in patients with OCD. With regard to other PDs and clusters, the results are inconsistent or the sample sizes are too small to reach a conclusion. OCD patients with different comorbid PDs differ in their therapeutic response to treatment. To optimize the treatment of OCD, the predictive value of PDs on the treatment outcome should be further investigated, and treatment of Axis I and II comorbidity requires more attention.

Sodium oxybate-induced central sleep apneas

Sodium oxybate (γ-hydroxybutyric acid, GHB) is a neurotransmitter in the human brain which exerts sedative effects and is used therapeutically in the treatment of narcolepsy. Current safety recommendations have been formulated for the use of GHB in patients with preexisting breathing disorders. We report the case of a 39-year-old female with narcolepsy and cataplexy revealing the de novo emergence of central sleep apneas in a Cheyne-Stokes pattern under constant treatment with GHB. After discontinuation of GHB, polysomnographic re-evaluation demonstrated the disappearance of central sleep apneas. To our knowledge, this is the first report of de novo central sleep apneas induced by GHB in a patient without pre-existing sleep-disordered breathing, suggesting that there is a need for further investigation and potentially an extension of the safety guidelines to patients without a pre-existing breathing disorder.

Insomnia does not appear to be associated with substantial structural brain changes

STUDY OBJECTIVES

Sleep has been demonstrated to significantly modulate brain plasticity and the manifestation of mental disorders. However, previous studies on the effect of disrupted sleep on brain structure have reported inconsistent results. The goal of the current study was to investigate brain morphometry in a well-characterized large sample of patients with primary insomnia (PI) in comparison with good sleeper controls.

DESIGN

Automated parcellation and pattern recognition approaches were supplemented by voxelwise analyses of gray and white matter volumes to analyze magnetic resonance images. All analyses included age, sex, and total intracranial volume as covariates.

SETTING

Department of Psychiatry and Psychotherapy of the University of Freiburg Medical Center.

PARTICIPANTS

There were 28 patients with PI (10 males; 18 females; age 43.7 ± 14.2 y) and 38 healthy, good sleepers (17 males; 21 females; age 39.6 ± 8.9 y).

INTERVENTIONS

N/A.

RESULTS

No significant between-group differences were observed in any of the investigated brain morphometry variables.

CONCLUSIONS

Altered brain function in insomnia does not appear to have a substantial effect on brain morphometry on a macroscopic level.

Steroid-responsive depression

A 48-year-old man presented with long-standing symptoms of major depression in the absence of markedly abnormal neurological findings or structural brain alterations. Antidepressive treatment, including medication and psychotherapy, had not led to significant improvement. The EEG, cerebrospinal fluid (CSF) analysis, fluorodeoxyglucose-positron emission tomography and neuropsychological testing showed pathological findings. An epileptic state provided further evidence for an organic encephalopathy. Extensively elevated thyroid-antibodies in the serum and CSF, as well as the rapid and sustained recovery after intravenous treatment with prednisolone, pointed to the diagnosis of a primarily psychiatric manifestation of a steroid responsive encephalopathy associated with autoimmune thyroiditis (SREAT).

Quality of life changes following inpatient and outpatient treatment in obsessive-compulsive disorder: a study with 12 months follow-up

BACKGROUND

Quality of life (QoL) is increasingly recognized as a critical outcome parameter in mental health studies. The aim of this study was to investigate different domains of the QoL in persons with obsessive-compulsive disorder (OCD) before and after a multimodal, disorder-specific in- and outpatient treatment.

METHODS

Data of 73 persons with OCD treated in an inpatient setting followed by outpatient treatment were analyzed. The World Health Organization Quality of Life abbreviated (a multidimensional measure of the QoL) and the Beck Depression Inventory were administered prior to (baseline) and 12 months after the inpatient treatment (follow-up).

RESULTS

At baseline, participants reported a significantly diminished psychological, social, physical, and global QoL compared to the German general population. Environmental QoL was not impaired in the present sample. The QoL was significantly improved at follow-up, except for social QoL, but remained below norm values. The QoL improvement was predicted by improvements of depressive symptoms.

CONCLUSIONS

The results indicate that persons with OCD suffer from a very low QoL. The QoL was significantly improved after 12 months of intensive state-of-the-art treatment. However, the QoL indices remained considerably lower than population norm values, indicating the need for additional research into novel treatment options for persons with OCD.

Neuroenhancement strategies for psychiatric disorders: rationale, status quo and perspectives

With the growing mechanistic understanding of higher brain functions like learning and memory, vigilance and social cognition, new pharmacological approaches for the treatment of psychiatric disorders arise. Substances used as neuroenhancers for the improvement of cognitive or emotional functions in healthy subjects might provide novel pharmacological opportunities in psychiatry. Intriguingly, drugs like modafinil, D-cycloserine or oxytocin have shown significant improvements in key symptoms in several psychiatric disorders. When used as augmentation strategies, they could either directly interfere with psychopathological impairments or improve response to other treatment modalities like psychotherapy or psychopharmacological drugs. While initial studies yielded promising results, further research on beneficial or adverse effects is required.

Mindfulness-based cognitive therapy in obsessive-compulsive disorder - a qualitative study on patients' experiences

BACKGROUND

Cognitive behavioral therapy (CBT) with exposure and response prevention (ERP) is the first-line treatment for patients with obsessive-compulsive disorder (OCD). However, not all of them achieve remission on a longterm basis. Mindfulness-based cognitive therapy (MBCT) represents a new 8-week group therapy program whose effectiveness has been demonstrated in various mental disorders, but has not yet been applied to patients with OCD. The present pilot study aimed to qualitatively assess the subjective experiences of patients with OCD who participated in MBCT.

METHOD

Semi-structured interviews were conducted with 12 patients suffering from OCD directly after 8 sessions of a weekly MBCT group program. Data were analyzed using a qualitative content analysis.

RESULTS

Participants valued the treatment as helpful in dealing with their OCD and OCD-related problems. Two thirds of the patients reported a decline in OCD symptoms. Benefits included an increased ability to let unpleasant emotions surface and to live more consciously in the present. However, participants also discussed several problems.

CONCLUSION

The data provide preliminary evidence that patients with OCD find aspects of the current MBCT protocol acceptable and beneficial. The authors suggest to further explore MBCT as a complementary treatment strategy for OCD.

Sleep-related arousal versus general cognitive arousal in primary insomnia

STUDY OBJECTIVES

The present study aimed at further investigating trait aspects of sleep-related cognitive arousal and general cognitive arousal and their association with both objective and subjective sleep parameters in primary insomnia patients.

METHODS

A clinical sample of 182 primary insomnia patients and 54 healthy controls was investigated using 2 nights of polysomnography, subjective sleep variables, and a questionnaire on sleep-related and general cognitive arousal.

RESULTS

Compared to healthy controls, primary insomnia patients showed both more sleep-related and general cognitive arousal. Furthermore, sleep-related cognitive arousal was closely associated with measures of sleep-onset and sleep-maintenance problems, while general cognitive arousal was not.

CONCLUSIONS

Cognitive-behavioral treatment for insomnia might benefit from dedicating more effort to psychological interventions that are able to reduce sleep-related cognitive arousal.

The timing of learning before night-time sleep differentially affects declarative and procedural long-term memory consolidation in adolescents

Sleep after learning has been shown to foster the consolidation of new memories. However, fundamental questions on the best timing of learning before night-time sleep persist. We tested the hypothesis that learning directly prior to night-time sleep compared to 7.5 hrs prior to night-time sleep provides better conditions for the consolidation of declarative and procedural memories. Fifty healthy female adolescents (aged 16-17 years) were trained on a declarative word-pair and a procedural finger-tapping task at 3 pm (afternoon group, n = 25) or at 9 pm (evening group, n = 25), followed by a sleep laboratory night. Retrieval was assessed 24 hours and 7 days after initial training. Subjects trained in the afternoon showed a significantly elevated retention rate of word-pairs compared to subjects trained in the evening after 24 hours, but not after 7 days. In contrast, off-line gains in finger-tapping performance were significantly higher in subjects trained in the evening compared to those trained in the afternoon after both retention intervals. The observed enhanced consolidation of procedural memories after training in the evening fits to current models of sleep-related memory consolidation. In contrast, the higher retention of declarative memories after encoding in the afternoon is surprising, appeared to be less robust and needs further investigation.

Scenario realism and welfare estimates in choice experiments--a non-market valuation study on the European water framework directive

Using choice experiment data for economic valuation we analyse how disbelief in survey information could affect the retrieved welfare estimates. We distinguish between two types of survey information to the respondents. The first type of information concerns the current environmental status of a water body. This information is provided prior to the valuation questions and the corresponding beliefs in the provided information are also elicited before valuation. The second type of information concerns the proposed improvements in the environmental status of the water body. We find that average welfare measures differ considerably according to whether respondents who disagree with the status quo levels and find proposed scenarios unlikely are included or not.

REM sleep instability--a new pathway for insomnia?

Chronic insomnia afflicts approximately 10% of the adult population and is associated with daytime impairments and an elevated risk for developing somatic and mental disorders. Current pathophysiological models propose a persistent hyperarousal on the cognitive, emotional and physiological levels. However, the marked discrepancy between minor objective alterations in standard parameters of sleep continuity and the profound subjective impairment in patients with insomnia is unresolved. We propose that "instability" of REM sleep contributes to the experience of disrupted and non-restorative sleep and to the explanation of this discrepancy. This concept is based on evidence showing increased micro- and macro-arousals during REM sleep in insomnia patients. As REM sleep represents the most highly aroused brain state during sleep it seems particularly prone to fragmentation in individuals with persistent hyperarousal. The continuity hypothesis of dream production suggests that pre-sleep concerns of patients with insomnia, i. e., worries about poor sleep and its consequences, dominate their dream content. Enhanced arousal during REM sleep may render these wake-like cognitions more accessible to conscious perception, memory storage and morning recall, resulting in the experience of disrupted and non-restorative sleep. Furthermore, chronic fragmentation of REM sleep might lead to dysfunction in a ventral emotional neural network, including limbic and paralimbic areas that are specifically activated during REM sleep. This dysfunction, along with attenuated functioning in a dorsal executive neural network, including frontal and prefrontal areas, might contribute to emotional and cognitive alterations and an elevated risk of developing depression.

Insomnia as a predictor of depression: a meta-analytic evaluation of longitudinal epidemiological studies

BACKGROUND

In many patients with depression, symptoms of insomnia herald the onset of the disorder and may persist into remission or recovery, even after adequate treatment. Several studies have raised the question whether insomniac symptoms may constitute an independent clinical predictor of depression. This meta-analysis is aimed at evaluating quantitatively if insomnia constitutes a predictor of depression.

METHODS

PubMed, Medline, PsycInfo, and PsycArticles databases were searched from 1980 until 2010 to identify longitudinal epidemiological studies simultaneously investigating insomniac complaints and depressed psychopathology. Effects were summarized using the logarithms of the odds ratios for insomnia at baseline to predict depression at follow-up. Studies were pooled with both fixed- and random-effects meta-analytic models in order to evaluate the concordance. Heterogeneity test and sensitivity analysis were computed.

RESULTS

Twenty-one studies met inclusion criteria. Considering all studies together, heterogeneity was found. The random-effects model showed an overall odds ratio for insomnia to predict depression of 2.60 (confidence interval [CI]: 1.98-3.42). When the analysis was adjusted for outliers, the studies were not longer heterogeneous. The fixed-effects model showed an overall odds ratio of 2.10 (CI: 1.86-2.38).

LIMITATIONS

The main limit is that included studies did not always consider the role of other intervening variables.

CONCLUSIONS

Non-depressed people with insomnia have a twofold risk to develop depression, compared to people with no sleep difficulties. Thus, early treatment programs for insomnia might reduce the risk for developing depression in the general population and be considered a helpful general preventive strategy in the area of mental health care.

Time will tell: a retrospective study investigating the relationship between insomnia and objectively defined punctuality

Primary insomnia is a prevalent sleep disorder affecting approximately 3% of the general population. Studies suggest that personality traits such as perfectionism and neuroticism might be implicated in the aetiology of the disorder. However, to date, no study has investigated behavioural indicators of these factors in a hypothesis-driven manner. In the present study, we assessed punctuality as a behavioural indicator of perfectionism and neuroticism in 635 consecutive clinical patients of the sleep laboratory of the Department of Psychiatry and Psychotherapy, University of Freiburg Medical Center. The primary aim was to compare primary insomnia patients (n = 148) with another group of patients with other sleep-related diagnoses (n = 487). Primary insomnia patients arrived on average 4 min earlier when compared to other patients (P = 0.041). However, this effect failed to reach statistical significance when correcting for the influence of potential confounding variables. Of note, we found a strong relationship between polysomnographic sleep parameters and punctuality. That is, short sleep duration was associated significantly with early arrival times at the sleep laboratory (P = 0.023). These findings support the proposal that personality traits, which we predict underlie obsessive punctuality, may be involved in the aetiology of objectively defined sleep disturbances. Clinical implications of the current results for cognitive behavioural treatments of insomnia are discussed.

Heart rate and heart rate variability in subjectively reported insomnia

According to epidemiological studies, insomnia is associated with cardiovascular mortality. However, it is yet to be determined whether this link is mediated by known cardiovascular risk factors. The current study aimed at investigating the association between primary insomnia, defined as subjectively reported sleep disturbance in the absence of any other pathology or substance intake, and alterations in polysomnographically determined nocturnal heart rate (HR) and heart rate variability (HRV). A total of 4,581 nocturnal short-term electrocardiographic recordings (5 min each) from 104 participants (58 with primary insomnia, 46 healthy controls) were evaluated for HR as well as for time and frequency domain measures of HRV. In the primary insomnia group, we found a lower wake-to-sleep HR reduction and a lower standard deviation of RR intervals (SDNN) compared to healthy controls. However, between-group differences in resting HR were not found, and previous results of an increase in sympathovagal balance and a decrease in parasympathetic nocturnal activity in objectively determined insomnia could not be confirmed in our sample of self-report insomnia patients. When restricting our analyses to insomnia patients with objectively determined short sleep duration, we found reduced parasympathetic activity as indicated by decreased high frequency power of HRV, as well as decreased root mean square of successive RRI differences (RMSSD) and percentage of successive RRIs that differ by more than 50 ms (pNN50) values. A lower wake-to-sleep HR reduction and alterations in HRV variables might, at least partially, mediate the increased rates of cardiovascular morbidity and mortality observed in insomnia patients.

Sleep restriction over several days does not affect long-term recall of declarative and procedural memories in adolescents

OBJECTIVES

There is broad evidence that sleep as opposed to waking facilitates the consolidation of both declarative and procedural memory. The current study addressed the question whether different extents of sleep restriction after learning would impair long-term memory consolidation in adolescents.

METHODS

Eighty-eight healthy adolescents were randomized to five different sleep protocols with 9, 8, 7, 6 or 5 h of time in bed for four consecutive nights under controlled conditions that excluded daytime sleep. Declarative (word-pair task) and procedural memory (mirror tracing task) encoding was assessed prior to the sleep restriction protocol. Recall was assessed after two recovery nights following the sleep protocol and 4 weeks later.

RESULTS

Sleep diaries and actigraphy data demonstrated that the participants closely followed the sleep protocols. There were no differences in demographic parameters or memory encoding at baseline. In contrast to the initial prediction, restriction of nocturnal sleep over four consecutive nights had no significant impact on declarative or procedural memory consolidation. Polysomnographic monitoring after sleep restriction demonstrated a high preservation of the amount of slow wave sleep in the restricted conditions.

CONCLUSIONS

The results suggest that adolescents show a high resilience of memory consolidation to substantial sleep curtailment across four nights that might be promoted by increased sleep intensity under conditions of sleep restriction.

Impaired memory consolidation during sleep in patients with functional memory disorder

Functional memory disorder (FMD) is characterized by mnestic and attentional deficits without symptoms of mild cognitive impairment or dementia. FMD usually develops in subjects with high psychosocial stress level and is classified to the somatoform disorders. We assessed memory performance (procedural mirror tracing task, declarative visual and verbal memory task) and other cognitive functions before and after one night of sleep in 12 FMD patients (mean age: 51.7 yrs, 7 females) and 12 healthy subjects matched for age, gender and IQ. Memory performance and other neurocognitive tasks did not differ between the groups at baseline. After one night of sleep, FMD patients showed an impairment of declarative memory consolidation compared to healthy subjects (visual task: p=0.004; verbal task: p=0.039). Spectral analysis of sleep-EEG indicated an increased cortical excitation in FMD. We hypothesize that a hyperarousal state in FMD might contribute to sleep disturbance implicating negative effects on declarative memory consolidation.

Learning as a model for neural plasticity in major depression

BACKGROUND

The neuroplasticity hypothesis of depression proposes that a dysfunction of neural plasticity-the basic ability of living organisms to adapt their neural function and structure to external and internal cues-might represent a final common pathway underlying the biological and clinical characteristics of the disorder. This study examined learning and memory as correlates of long-term synaptic plasticity in humans to further test the neuroplasticity hypothesis of depression.

METHODS

Learning in three tasks, for which memory consolidation has been shown to depend on local synaptic refinement in areas of interest (hippocampus-dependent declarative word-pair learning, amygdala-dependent fear conditioning, and primary-cortex-dependent visual texture discrimination), was assessed in 23 inpatients who met International Classification of Disease, 10th Revision, criteria for severe unipolar depression and 35 nondepressed comparison subjects.

RESULTS

Depressed subjects showed a significant deficit in declarative memory consolidation and enhanced fear acquisition as indicated by skin conductance responses to conditioned stimuli, in comparison with nondepressed subjects. Depressed subjects demonstrated impaired visual discrimination at baseline, not allowing for valid group comparisons of gradual improvement, the plasticity-dependent phase of the task.

CONCLUSIONS

The results of the study are consistent with the neuroplasticity hypothesis of depression, showing decreased synaptic plasticity in a dorsal executive network that comprises the hippocampus and elevated synaptic plasticity in a ventral emotional network that includes the amygdala in depression. Evaluation of further techniques aimed at modulating synaptic plasticity might prove useful for developing novel treatments for major depressive disorder.

Sleep and memory in healthy children and adolescents - a critical review

There is mounting evidence that sleep is important for learning, memory and the underlying neural plasticity. This article aims to review published studies that evaluate the association between sleep, its distinct stages and memory systems in healthy children and adolescents. Furthermore it intends to suggest directions for future research. A computerised search of the literature for relevant articles published between 1966 and March 2008 was performed using the keywords "sleep", "memory", "learn", "child", "adolescents", "adolescence" and "teenager". Fifteen studies met the inclusion criteria. Published studies focused on the impact of sleep on working memory and memory consolidation. In summary, most studies support the hypothesis that sleep facilitates working memory as well as memory consolidation in children and adolescents. There is evidence that performance in abstract and complex tasks involving higher brain functions declines more strongly after sleep deprivation than the performance in simple memory tasks. Future studies are needed to better understand the impact of a variety of variables potentially modulating the interplay between sleep and memory, such as developmental stage, socioeconomic burden, circadian factors, or the level of post-learning sensory and motor activity (interference). This line of research can provide valuable input relevant to teaching, learning and public health policy.

The impact of sleep-related attentional bias on polysomnographically measured sleep in primary insomnia

STUDY OBJECTIVES

Although sleep-related attentional bias has been shown to be evident in primary insomnia, the association with objectively measured sleep has not been investigated. In the present study, we used polysomnography (PSG) to fill this void.

DESIGN

Patients with primary insomnia and healthy controls were studied using a visual dot probe task (VDP) and an emotional Stroop task (EST). Additionally, polysomnography was carried out in a sub-sample (n = 22) of patients in the subsequent night.

SETTING

Department of Psychiatry and Psychotherapy of the University of Freiburg Medical Center.

PARTICIPANTS

Thirty patients with primary insomnia and 30 matched healthy controls.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Patients with primary insomnia demonstrated a significant sleep-related attentional bias compared to controls in the EST but no significant group effects were found for the VDP. VDP attentional bias scores were positively correlated with measures of sleep pressure, including total sleep time, sleep efficiency, and the amount of slow wave sleep. EST attentional bias scores were not correlated with subsequent PSG parameters, and we did not observe a correlation between attentional bias scores on the two tasks.

CONCLUSIONS

The unexpected relationship between increased attentional bias, in the VDP task, and improved markers of sleep duration and continuity, may be indicative of a homeostatic craving for sleep in those with high attentional bias. This awaits further testing in multiple night studies, to shed light on the mechanisms and implications of sleep-related attentional bias.

Memory before and after sleep in patients with moderate obstructive sleep apnea

OBJECTIVE

The aim of this study was to investigate the effects of obstructive sleep apnea (OSA) on procedural and declarative memory encoding in the evening prior to sleep, on memory consolidation during subsequent sleep, and on retrieval in the morning after sleep.

METHODS

Memory performance (procedural mirror-tracing task, declarative visual and verbal memory task) and general neuropsychological performance were assessed before and after one night of polysomnographic monitoring in 15 patients with moderate OSA and 20 age-, sex-, and IQ-matched healthy subjects.

RESULTS

Encoding levels prior to sleep were similar across groups for all tasks. Conventional analyses of averaged mirror tracing performance suggested a significantly reduced overnight improvement in OSA patients. Single trial analyses, however, revealed that this effect was due to significantly flattened learning curves in the evening and morning session in OSA patients. OSA patients showed a significantly lower verbal retention rate and a non-significantly reduced visual retention rate after sleep compared to healthy subjects. Polysomnography revealed a significantly reduced REM density, increased frequency of micro-arousals, elevated apnea-hypopnea index, and subjectively disturbed sleep quality in OSA patients compared to healthy subjects.

CONCLUSIONS

The results suggest that moderate OSA is associated with a significant impairment of procedural and verbal declarative memory. Future work is needed to further determine the contribution of structural or functional alterations in brain circuits relevant for memory, and to test whether OSA treatment improves or normalizes the observed deficits in learning.