Sleep Medicine Reviews

Past success and future growth

Michael V. Vitiello, Jean Krieger — 2012-02-01

Welcome to the 16th volume of Sleep Medicine Reviews (SMR). Once again we offer our heartfelt thanks to all of our readers, as 2011 was another very successful year for SMR. Last year SMR brought you issues focused on sleep questionnaire development, obesity hypoventilation syndrome, rapid eye movement (REM) sleep, infant sleep, sleep walking and continuous positive airway pressure (CPAP) adherence. SMR Volume 15 contained: six guest editorials; 26 clinical reviews, providing the state-of-the-art on a wide range of clinical conditions; 5 physiological reviews, which continued our series of reviews focusing on the neurohormonal regulation of sleep and wakefulness; 4 theoretical reviews, and several commentaries and replies.

Definition of acute insomnia: Diagnostic and treatment implications

Charles M. Morin — 2012-02-01

The experience of acute insomnia is probably a universal phenomenon during the course of human life, particularly when exposed to a significant life event, a sudden illness, or a rapid change in sleep schedule. Whether such sleep difficulties remain time-limited or evolve into a chronic problem is likely to vary across individuals as a function of predispositions, coping skills, and life circumstances. Should acute insomnia be considered a normal reaction to stress or a sleep disorder in need of treatment? What is the best case definition of acute insomnia in terms of onset, duration, frequency and intensity? These questions have important implications for diagnosis and treatment of insomnia as well as for tracking its natural history.

Acute insomnia: Current conceptualizations and future directions

2012-02-01

Summary: Despite significant contributions made in the area of persistent/chronic insomnia, especially with regard to the underlying mechanisms driving its maintenance, the area of acute insomnia has received comparatively little attention. The aim of this paper is to review the literature with regard to understanding the situational and personaological circumstances that surround the development of acute insomnia. The review begins by examining how the existing diagnostic systems conceptualise acute insomnia. Theoretical models that explain, or inferentially explain, the transition between normal sleep and acute insomnia are then explored and evaluated. The review then examines the current evidence base in terms of the pathogenesis of acute insomnia from naturalistic and experimental studies. Overall, the findings from the review confirm the paucity of evidence available but perhaps more importantly highlight the need for a structured diagnosis of acute insomnia as the first step in a research and treatment strategy. To this end a diagnostic system, drawing on the existing literature on stress and the systems used to diagnose depression, is forwarded and justified and a research agenda advanced.

Sleep disturbances in sexual abuse victims: A systematic review

2012-02-01

Summary: An impressive body of research has investigated whether sexual abuse is associated with sleep disturbances. Across studies there are considerable differences in methods and results. The aim of this paper was to conduct the first systematic review of this area, as well as to clarify existing results and to provide guidelines for future research. We conducted searches in the electronic databases PsycINFO and PubMed up until October 2010 for studies on sleep disturbances in sexually abused samples. Thirty-two studies fulfilled the inclusion criteria (reported empirical data, included sexually abused subjects, employed some form of sleep measurement, English language and published in peer reviewed journals). Across the studies included, sleep disturbances were widespread and more prevalent in sexually abused subjects as compared to in non-abused samples. Symptoms reported more frequently by sexually abused samples included nightmare related distress, sleep paralysis, nightly awakenings, restless sleep, and tiredness. Results were divergent with regards to sleep onset difficulties, nightmare frequency, nocturnal activity, sleep efficiency, and concerning the proportion of each sample reporting sleep disturbances as such. Potential sources of these divergences are examined. Several methodological weaknesses were identified in the included studies. In order to overcome limitations, future researchers are advised to use standardized and objective measurements of sleep, follow-up or longitudinal designs, representative population samples, large sample sizes, adequate comparison groups, as well as comparison groups with other trauma experiences.

Cyclic alternating pattern (CAP): The marker of sleep instability

Liborio Parrino, Raffaele Ferri, Oliviero Bruni, Mario G. Terzano — 2012-02-01

Summary: Cyclic alternating pattern CAP is the EEG marker of unstable sleep, a concept which is poorly appreciated among the metrics of sleep physiology. Besides, duration, depth and continuity, sleep restorative properties depend on the capacity of the brain to create periods of sustained stable sleep. This issue is not confined only to the EEG activities but reverberates upon the ongoing autonomic activity and behavioral functions, which are mutually entrained in a synchronized oscillation. CAP can be identified both in adult and children sleep and therefore represents a sensitive tool for the investigation of sleep disorders across the lifespan. The present review illustrates the story of CAP in the last 25 years, the standardized scoring criteria, the basic physiological properties and how the dimension of sleep instability has provided new insight into pathophysiolology and management of sleep disorders.

Heart rate variability, sleep and sleep disorders

Phyllis K. Stein, Yachuan Pu — 2012-02-01

Summary: Heart rate (HR) is modulated by the combined effects of the sympathetic and parasympathetic nervous systems. Therefore, measurement of changes in HR over time (heart rate variability or HRV) provides information about autonomic functioning. HRV has been used to identify high risk people, understand the autonomic components of different disorders and to evaluate the effect of different interventions, etc. Since the signal required to measure HRV is already being collected on the electrocardiogram (ECG) channel of the polysomnogram (PSG), collecting data for research on HRV and sleep is straightforward, but applications have been limited. As reviewed here, HRV has been applied to understand autonomic changes during different sleep stages. It has also been applied to understand the effect of sleep-disordered breathing, periodic limb movements and insomnia both during sleep and during the daytime. HRV has been successfully used to screen people for possible referral to a Sleep Lab. It has also been used to monitor the effects of continuous positive airway pressure (CPAP). A novel HRV measure, cardiopulmonary coupling (CPC) has been proposed for sleep quality. Evidence also suggests that HRV collected during a PSG can be used in risk stratification models, at least for older adults. Caveats for accurate interpretation of HRV are also presented.

Circadian rhythms, sleep, and substance abuse

Brant P. Hasler, Leisha J. Smith, Jennifer C. Cousins, Richard R. Bootzin — 2012-02-01

Summary: Substance abuse is linked to numerous mental and physical health problems, including disturbed sleep. The association between substance use and sleep appears to be bidirectional, in that substance use may directly cause sleep disturbances, and difficulty sleeping may be a risk factor for relapse to substance use. Growing evidence similarly links substance use to disturbances in circadian rhythms, although many gaps in knowledge persist, particularly regarding whether circadian disturbance leads to substance abuse or dependence. Given the integral role circadian rhythms play in regulating sleep, circadian mechanisms may account in part for sleep–substance abuse interactions. Furthermore, a burgeoning research base supports a role for the circadian system in regulating reward processing, indicating that circadian mechanisms may be directly linked to substance abuse independently of sleep pathways. More work in this area is needed, particularly in elucidating how sleep and circadian disturbance may contribute to initiation of, and/or relapse to, substance use. Sleep and circadian-based interventions could play a critical role in the prevention and treatment of substance use disorders.

Insomnia and daytime cognitive performance: A meta-analysis

Émilie Fortier-Brochu, Simon Beaulieu-Bonneau, Hans Ivers, Charles M. Morin — 2012-02-01

Summary: Objectives: Individuals with insomnia consistently report difficulties pertaining to their cognitive functioning (e.g., memory, concentration). However, objective measurements of their performance on neuropsychological tests have produced inconsistent findings. This meta-analysis was conducted to provide a quantitative summary of evidence regarding the magnitude of differences between individuals with primary insomnia and normal sleepers on a broad range of neuropsychological measures.Methods: Reference databases (PubMed, PsycInfo, Dissertation Abstracts International) were searched for studies comparing adults with primary insomnia to normal sleepers on neuropsychological measures. Dependent variables related to cognitive and psychomotor performance were extracted from each study. Variables were classified independently by two licensed neuropsychologists according to the main cognitive function being measured. Individual effect sizes (Cohen's d) were weighted by variability and combined for each cognitive function using a fixed effects model. Average effect sizes and their 95% confidence intervals were computed for each cognitive function.Results: Twenty-four studies met inclusion criteria, for a total of 639 individuals with insomnia and 558 normal sleepers. Significant impairments (p<0.05) of small to moderate magnitude were found in individuals with insomnia for tasks assessing episodic memory (ES=−0.51), problem solving (ES=−0.42), manipulation in working memory (ES=−0.42), and retention in working memory (ES=−0.22). No significant group differences were observed for tasks assessing general cognitive function, perceptual and psychomotor processes, procedural learning, verbal functions, different dimensions of attention (alertness, complex reaction time, speed of information processing, selective attention, sustained attention/vigilance) and some aspects of executive functioning (verbal fluency, cognitive flexibility).Conclusion: Individuals with insomnia exhibit performance impairments for several cognitive functions, including working memory, episodic memory and some aspects of executive functioning. While the data suggests that these impairments are of small to moderate magnitude, further research using more ecologically valid measures and normative data are warranted to establish their clinical significance.

Forerunners of REM sleep

Hartmut Schulz, Piero Salzarulo — 2012-02-01

Summary: The development of sleep research can be divided into two main periods. The first one was initiated in 1863 by the first systematic measurement of the depth of sleep, the second in 1953 by the discovery of recurrent episodes of rapid eye movements in sleep. The main methodological procedure in the first of these two periods was the measurement of a single physiological variable, while beginning with long-term measurements of the electroencephalogram (EEG) in sleep, multi-channel, polygraphic recording became the method of choice for sleep studies. Although rhythmic changes in the ultradian frequency range of one to 2 h were observed early in many variables during sleep (movements, autonomic functions, penile erections), the recognition of the existence of two different states of sleep (rapid eye movement (REM) and non-rapid eye movement (NREM sleep)) was contingent upon a ‘synthetic’ view, which focus on the coalescence of multiple variables. The dual concept of sleep organization evolved stepwise in parallel to the rapid growth of neurophysiological knowledge and techniques in the first half of the 20th century, culminating in the discovery of REM sleep.

REM sleep could have no adaptive value

2012-02-01

Last June, this journal published an interesting guest review by JM Siegel on the paradoxical aspects of rapid eye movement (REM) sleep where a detailed update of the main signs of REM sleep in humans and animals as well as their eventual adaptive meaning. However, the author recognized that.“The unraveling of some to the REM sleep circuitry may give the impression that the paradox of REM sleep has been solved. But, alas, it remains. We do not know what conditions turn REM sleep on and what presumably fulfilled condition turns it off. So we now know many of the “players” in REM sleep control, but we really still don’t know their “game.”

REM sleep must have an adaptive value

Jerome M. Siegel — 2012-02-01

REM sleep has several characteristics that make it highly unlikely that it has “no adaptive value.” First, brain metabolic activity is high in REM sleep, comparable to or exceeding waking values. This is in contrast to non-REM sleep during which brain metabolism is greatly reduced. Brain metabolism constitutes approximately 25% of body energy consumption in humans at rest. It seems clear that animals that had reduced amounts of REM sleep would have a selective advantage over those that had higher amounts. This would lead to an eventual elimination of REM sleep, since energy consumption is, for most animals, the most critical issue determining the likelihood of survival and reproduction.

Peer Reviewers Volume 15

2012-02-01

The Co-Editors-in-Chief wish to thank these individuals for their expertise in ensuring the quality of Sleep Medicine Reviews. A