Introduction: Historical Landmarks and Current Status of Sleep Research and Practice: An Introduction to the Timeliness, Aims, and Scope of this Handbook
Abstract and Keywords
The purpose of this brief, introductory chapter is to “set the scene” for the handbook. We start by providing some historical context on the understanding of sleep across the ages, from ancient times through to more contemporary landmarks. From this we learn that sleep has always been a fascinating subject. It captivated the thinking of early philosophers and emerged as a subject of scientific interest in medieval times. However, many of the discoveries that have begun to unlock the mysteries of sleep have taken place within living memory. We also foreshadow the current status of sleep research and practice that forms the substance of the handbook. These are exciting times, not least for psychologists and cognitive behavioral scientists. A great deal of progress has been made in the characterization, assessment, and treatment of sleep disorders in recent years, and the new discipline of behavioral sleep medicine has grown out of this scientist–practitioner emphasis. The chapter concludes with an outline of the aims and scope of the handbook and an overview of its main sections. We also introduce each chapter and its author(s). We hope that you will find the handbook stimulating and helpful in your clinical and research practice.
History and landmarks
We all sleep, and we all must sleep. Indeed, sleep is by no means an exclusive feature of human physiology and behavior. All other mammals sleep too, albeit in some cases with adaptations. For example, prey species may have to delay sleep for periods of time to avoid being eaten, and the blind Indus dolphin sleeps in very short bursts to ensure safe navigation. Insects like the fruit fly also display sleep-like states in their rest–wake cycles. Indeed, it is fair to say that sleep, in some form, appears to provide restoration for all living organisms. Even plants have a time-keeping, circadian clock mechanism, allowing them to “anticipate” daily changes in light and temperature. Despite such seemingly universal imperatives, the study of sleep processes and functions is still in its infancy. The same applies to our understanding of disorders of sleep. Nevertheless, it is a fascinating scientific and clinical area, and progress is certainly being made.
An early history of sleep
Of course we know relatively little about sleep in primitive times, but we can deduce enough to be certain that sleep is no modern invention! For example, it has been suggested that Neanderthal man (70,000 to 40,000 BC) may have represented a transitional stage between the non-human primate pattern, which was of polyphasic sleep (multiple rest–activity cycles in a 24-hour period) and the monophasic pattern (sleep at night, awake by day) that we are familiar with in modern times. Monophasic sleep is thought to have become dominant in the Neolithic period (10,000 BC). By the time we come to the early civilizations of Mesopotamia, India, Egypt, and China, people appear to have been aware of the importance of sleep and dreams, with documented remedies ranging from divination and chanting to blood-letting, and the use of medicinal plants to promote sleep or wakefulness. Indeed, the yin-yang symbol attributed to the (p. 2) ancient Chinese (ca. 2900 BC) was adopted by the American Sleep Disorders Association (now the American Academy of Sleep Medicine) as its emblem.
Likewise, there are many references to sleep in ancient literature. The Bible, for example, refers to sleep being associated with contentment and hard work but also with laziness, and dreaming is seen as a means of communication between God and man in many religions. The Greek philosopher Hippocrates (ca. 460 BC) suggested that sleep resulted from blood moving from the limbs to be warmed in the “inner regions” of the body. Aristotle in the 4th century BC believed that dreams were portents of the future, but also suggested that the ingestion of food indirectly induced sleepiness by taking heat away from the brain. Sleep was also used as a synonym for death in ancient Rome and Greece by poets such as Homer and Ovid.
Moving on to more recent times, by the end of the first millennium a scientific influence had become more dominant, reducing the previous emphasis on philosophy and mysticism. The uses of medicinal plants continued, but behavioral recommendations also began to emerge. For example, the Jewish philosopher Maimonides in the 12th century stated that “the day and night consist of 24 hours. It is sufficient for a person to sleep one third thereof, which is 8 hours. These should be at the end of the night so that from the beginning of sleep until the rising of the sun will be 8 hours. Thus he will arise from bed before the sun rises.” A theory on sleep mechanisms was proposed by René Descartes in the 17th century. His hydraulic model of sleep suggested that the pineal gland helped to maintain alertness and that the “loss of animal spirit” from the pineal gland caused the ventricles to collapse, thereby inducing sleep. Thomas Willis and Thomas Sydenham a little later first developed what might be seen as the emergent clinical neurology of sleep, with work including the first references to restless legs syndrome, and also contributions on nightmares and insomnia.
Some modern landmarks in our understanding of sleep
Some of these latter insights are suggested by Dement (1998) to have occurred too early to be exploited by the as-yet-unborn field of sleep medicine. In this context he also mentions other scientific landmarks such as the demonstration of the persistence of circadian rhythms in the absence of environmental cues by De Mairan (1729), and Gellineau’s publication of a description of the narcolepsy syndrome in 1880. Likewise, Caton demonstrated electrical rhythm in the brains of animals in 1875, and Hans Berger’s early descriptions of the differences between brain wave patterns in awake and sleeping brains continued the perspective that sleep was essentially the brain turned off, the so-called “passive process theory.”
Since the early 1950s, discoveries about sleep seem to have increased almost exponentially, revealing that sleep is a varied, complex, and active arrangement of processes. Starting with the “discovery” of rapid eye movement (REM) sleep in 1952 by Aserinsky and Kleitman, the relationship between eye movements and dream activity was reported by Dement, who later also demonstrated the effects of sleep deprivation upon REM sleep in 1960. At around the same time, Jouvet showed that, during REM sleep, the voluntary muscle groups are essentially paralyzed, and by the mid 1960s the essential features of sleep had become established to the extent that a standardized manual for the scoring of human sleep had been published by Rechtschaffen and Kales. In parallel to the growing recognition of the importance of “homeostatic regulation”—sleep deprivation leads to growing sleep debt and increased pressure to sleep—seminal work was being carried out looking at circadian influences relating to sleep and wake timing: the so-called “body clock.” As early as 1938, Kleitman and his graduate student had conducted heroic personal experiments on circadian function by sleeping for a month in the depths of Mammoth Cave (Kentucky). They were trying to find out if our 24-hour rhythm is simply a reaction to environmental circumstances. However, it was not until the 1960s that Aschoff described the complexity of the cyclic sleep–wake pattern. Borbély (1982) would later publish his “two-process model” of sleep regulation, demonstrating the interaction between homeostatic and circadian functions. The discipline of chronobiology was now well and truly born.
Extending from the work of Konopka and Benzer on fruit flies in the early 1970s, other researchers over the past 30 years (e.g., Rosbash, Young, Takahashi) have provided clear evidence of specific “clock genes.” Despite the fact that we live in a 24-hour world, it is of considerable interest that the human biological clock appears to be set slightly longer than 24 hours. The discovery that people who are cortically blind would naturally follow what is called a “free-running schedule” with progressive phase delay in their sleep onset has been associated (p. 3) with recognition that our circadian system is influenced by the availability of light to “entrain” the sleep–wake cycle to a 24-hour period, with the endogenous hormone melatonin playing a crucial role in the timing of sleep and wakefulness. The interaction of the sleep homeostat with circadian timing mechanisms is now recognized as a mutual feedback process (Czeisler, Dijk), and highly productive laboratory studies have gone on to demonstrate a relationship between circadian physiology, sleepiness, and human performance.
Interest in the phenomenon of sleepiness has evolved from distinctive scientific and clinical areas of enquiry. From those who were interested in the essential nature of sleepiness, its causes, and its consequences (such as Dinges), to those who became particularly interested in the risks associated with undertaking waking tasks while sleepy (not least driving; Phillips; Akerstedt; Mitler) and those who were interested in sleep disorders where excessive daytime sleepiness was a hallmark feature. Sleep apnea was reported independently by two research groups in France and Germany in 1965, following Lugaresi’s recognition of the relationship between hypersomnia and periodic breathing. The most important development in the treatment of obstructive sleep apnea (OSA), however, came from Australia in the 1980s, where Sullivan developed a novel but simple preventive treatment that has become known as CPAP (continuous positive airway pressure).
Excessive daytime sleepiness is also the cardinal feature of the primary hypersomnia problem that has become widely known as narcolepsy. As previously mentioned, clinical descriptions of narcolepsy have been available for a very long time, but it was not until the early 1970s that canine narcolepsy provided a unique animal model in which to study the disorder. The discovery of a hypocretin/orexin mutation in narcoleptic Doberman pinchers (Mitler) later led to the observation that narcolepsy is associated with HLA-DR2 and the hypothesis that narcolepsy may result from an autoimmune insult to the central nervous system. It is now known that complex HLA-DR and DQ interactions confer risk of the narcolepsy with cataplexy syndrome (Mignot).
Excellent and very readable overviews of such early influential times have been published by William Dement (The Promise of Sleep) and by Peretz Lavie (The Enchanted World of Sleep), and these books are recommended to the reader. Changing social and cultural factors are also very important—just consider for example the influence of the invention of the light bulb and the subsequent widespread availability of electric light. Those interested in sleep through the ages will also find fascinating insights in Michael Thorpy’s A History of Sleep in Man.
Insomnia and the past 50 years
Before closing this section on landmarks, it is important not to neglect the most common sleep disturbance of all: insomnia.
Modern approaches to the management of insomnia have been dominated by pharmacological agents, certainly until the early 1970s. In the 19th century, bromides and chloral hydrate were primarily used, later supplanted by barbiturates in the first half of the 20th century. Though effective as sleep aids, barbiturates proved to be dangerously addictive and very unsafe in overdose. Consequently, scientists developed a new group of drugs known as benzodiazepines, which, although safer in profile, nonetheless proved problematic in withdrawal. Some also had troublesome carryover effects, and so “z” drug variants called benzodiazepine receptor agonists became more popular from the 1990s onward. The potential role of pharmaceutical-grade melatonin has also attracted increasing interest in the past 15 years with the development and testing of melatonin receptor agonists. More recently still, there has been interest in orexin antagonist drugs for insomnia. Worryingly, however, in real-world practice much of the prescribing for insomnia is now off-label, that is, with drugs designed for another purpose but that have sedative side effects, such as sedative antidepressant medications (Feren, Schweitzer, & Walsh, 2011).
From a behavioral perspective, pioneering work in the 1970s by Bootzin, who recognized that sleep falls under the control of operant principles, and by Hauri and de la Peña, who recognized the psychophysiological nature of insomnia and the so-called “reverse first night effect,” respectively, spawned interest in insomnia amongst psychologists. Such models led to greater interest in insomnia as a disorder of hyperarousal (e.g., Bonnet, Nofzinger) and in the crucial role of cognitive factors (e.g., Borkovec) in its genesis and maintenance. Not surprisingly, variants of relaxation were among the first forms of psychological treatment along with paradoxical logotherapeutic methods (Ascher) and further developments of Bootzin’s stimulus control model. The 1980s saw the emergence of the extended stress-diathesis model of (p. 4) insomnia and a novel intervention based on time-in-bed restriction (Spielman & Glovinsky). It was around this time that we (Espie, Morin) and others (e.g., Lack, Edinger) came into the field, conducting clinical trials of insomnia interventions across a range of populations. Gradually, a more integrated cognitive behavioral framework of insomnia has emerged. The first head-to-head studies of CBT versus pharmacotherapy were published in the 1990s and later repeated when the newer benzodiazepine receptor agonist medications became more popular in the early 2000s. Both types of treatment showed short-term benefits, but psychological and behavioral approaches have consistently demonstrated superiority in longer-term outcomes (Riemann & Perlis, 2009), being endorsed as such since the 1990s in national guideline documents (e.g., NIH in the U.S., and NICE and BAP in the UK).
Over the past 20 years, research on insomnia has progressed in several ways. There have been important advances in measurement using patient-reported outcomes. This began substantially with the publication of the Pittsburgh Sleep Quality Index (Buysse), and later with the Insomnia Severity Index (Morin). Likewise there has been progress in understanding cortical correlates of insomnia through studies using quantitative EEG analysis (e.g., Perlis, Jacobs) and brain imaging (e.g., Nofzinger, Riemann, van Someren). We also better understand the epidemiology of insomnia (Ohayon, Lichstein) and its societal impact, and have robust research diagnostic criteria (Edinger) to apply across a range of study methodologies. There has also been a return to the experimental laboratory, investigating arousal/de-arousal mechanisms that could be important in the genesis and maintenance of insomnia. Studies range from the role of perception, worry, and cognition (Harvey), attentional inhibitory mechanisms (Espie), and cortical arousal conditioning (Perlis) to animal models of insomnia (Saper, Cano). There continues to be a primary focus upon CBT interventions, but there is growing interest also in other forms of psychotherapy, particularly the so-called “third wave” therapies including Mindfulness and Acceptance and Commitment Therapy (e.g., Lundh, Ong, Gross). There is also some novel work using in-lab reconditioning treatments such as Intensive Sleep Retraining (Lacks).
Current status of sleep research and clinical practice
It is clear that much progress has been made in understanding sleep and its disorders. Thinking particularly on the “behavioral” side of sleep research, candidate models and mechanisms associated with the development and persistence of insomnia have been proposed, and effective treatments have been developed and tested. However, behavioral sleep medicine has emerged as an area of special emphasis, conveying a broader interest, beyond insomnia, to other disorders of sleep and wakefulness, and beyond CBT to other possibilities for intervention.
Beyond an interest in insomnia
Some examples include important work on REM and NREM parasomnias, where psychophysiological models and treatments seem as relevant as they do in insomnia (Germain, Krakow). Nightmares associated with PTSD and the exacerbation of sleepwalking or night terrors at times of stressful change seem appropriate territory for psychological formulation and treatment. Other examples include circadian aspects of normal and dysregulated sleep where behavior, lifestyle, mental health, or disability factors may reciprocally influence circadian physiology through social timing and patterning as well as through exposure to light cues. Such biopsychosocial models can also inform care provision for vulnerable groups.
We know from many fields of health care that behavior change is challenging. Prescribing the “solution” is often relatively easy. Having a plan to eat well, lose weight, exercise more, stop smoking, and drink only in moderation is both a personal and national pastime. But turning knowledge and intention into healthy behavior is difficult and is mostly neglected in traditional medical practice. Consider nCPAP as a treatment for OSA. The treatment is a simple mechanical one to maintain physiological function: keep the airway open and you will breathe normally during sleep—but treatment implementation is essentially behavioral. Research on predictors of outcome tells us that using the mask leads to improvement, whereas not using it does not lead to improvement. Health psychology and behavior change models are beginning to be influential here (e.g., Aloia, Bartlett).
We will have more to say in the final chapter on the research agenda looking ahead. However, it is already clear that seeing sleep disorders as psychophysiological propositions may be an important theme. Within the psychological component we need to consider perception, attention, memory, learning, reasoning, contemplation, action, adherence, and relapse on the cognitive behavioral plane; we also need to consider meaning, values, relationships, (p. 5) mood, and sense of control on the emotional plane. These are just examples, not an exhaustive list. Likewise, when it comes to the disorders themselves, we have to recognize the importance of phenotypes (and homogeneity) while accounting for individual differences (heterogeneity), so that ultimately we may answer complex questions such as “How much of what will effect which changes in whom?” and “Why, how, and when will these effects happen?” Moreover, to continue to move the field forward, it will be important to have larger studies on better defined populations using common methodologies that integrate psychology and neuroscience approaches (e.g., van Someren, Riemann) and to make better use of experimental paradigms such as those that have guided the discovery that memory functions are sleep-stage dependent (e.g., Walker, Drummond).
Professional societies and learned journals
Associated with such progress in sleep research, and bridging across to progress in sleep medicine, there are now six firmly established specialized journals that have the word “sleep” in their title. The official journal of the European Sleep Research Society, the Journal of Sleep Research was first issued in 1992 (http://www.wiley.com/bw/journal.asp?ref=0962-1105&site=1), and Sleep and Biological Rhythms (published by the Asian Sleep Research Society) was first published in 2003 (http://www.blackwellpublishing.com/journal.asp?ref=1446-9235&site=1). With an even longer history, SLEEP, the house journal of the American Academy of Sleep Medicine, has been in continuous publication since 1978 (http://www.journalsleep.org/). Moreover, in 2005, the Journal of Clinical Sleep Medicine was added to the AASM stable (http://www.aasmnet.org/jcsm/). Sleep Medicine Reviews (http://www.elsevier.com/wps/find/journaldescription.cws_home/623074/description#description) and Sleep Medicine (http://www.elsevier.com/wps/find/journaldescription.cws_home/620282/description#description) became available in 1997 and 2000, respectively, and the specialized journal Behavioral Sleep Medicine was first published in 2003 (http://www. informaworld.com/smpp/title∼content=t775648093∼db=all). The gross effect of this expansion in journal publication is that in 2010 alone there were around 600 papers published on sleep across these six journals alone, with many more of course appearing elsewhere. It should be noted, in addition, that some of the national sleep societies produce other publications that contain valuable science and professional information. A notable example of this is the Sleep Research Society’s SRS Bulletin, which was in its 17th year of publication in 2011.
Another fundamental link between research and practice is education. In the U.S., the American Academy of Sleep Medicine (www.aasmnet. org/) and the Sleep Research Society (http://www.sleepresearchsociety.org/) work together on many educational activities, not the least of which is the Association of Professional Sleep Societies’ meeting (now simply called “SLEEP”), held in the early summer every year. This meeting now attracts around 6,000 delegates. Some other continental and national societies, like the European Sleep Research Society (www.esrs.eu/cms/) and the Canadian Sleep Society (www.css.to/), continue to have both basic sleep research and clinical research and practice integrated within the same society. The World Federation of Sleep Research and Sleep Medicine Societies (www.wfsrsms.org/), now abbreviated to the World Sleep Federation, provides an overarching organizational structure for the sleep research societies worldwide and holds quadrennial scientific meetings. The WFS Governing Council is the ruling group made up of delegates from member societies (ESRS, ASA, ASRS, SRS, AASM, CSS, and FLASS), thus representing over 10,000 researchers and clinicians involved in the sleep field worldwide. The World Sleep Federation was founded in 1987. More recently, the World Association of Sleep Medicine (www.wasmonline.org/) was founded to provide further impetus to clinical aspects of sleep and the advancement of sleep health worldwide.
Over the past 50 years, there has also been a worldwide growth of sleep medicine centers, dedicated to the assessment and treatment of sleep disorders. The most enlightened sleep centers are truly interdisciplinary in nature, comprising physicians, clinical psychologists, nurses, technologists, and a wide range of other professionals including dentists, physiologists, and educationalists. The medical profession has been the first to incorporate sleep into the curriculum for formal training; for example, the American Medical Association now recognizes sleep medicine as a sub-specialty area. Likewise, the American Academy of Sleep Medicine, having for a while acknowledged behavioral sleep medicine as an emerging area, has recently incorporated the Society for Behavioral Sleep Medicine (http://www.behavioralsleep.org/) in the following terms: “Behavioral Sleep Medicine is the field of clinical practice and scientific inquiry that encompasses: the study of behavioral, psychological, and physiological factors underlying normal and disordered sleep across the life span; (p. 6) and, the development and application of evidence-based behavioral and psychological approaches to the prevention and treatment of sleep disorders and co-existing conditions.” A similar approach is developing in other countries as well. The European Sleep Research Society, for example, is involved in the development of a core curriculum for specialists from diverse professional backgrounds and will ultimately license physicians, psychologists, nurses, scientists, and sleep technologists. National societies within the framework of WSF are also involved in the accreditation of sleep centers as clinical and research environments.
Another feature of the work of national societies has been the commissioning and reporting of guideline groups to review scientific evidence in different fields of sleep medicine practice. Papers arising from this work, like the AASM Practice Parameter statements, are regularly published in scientific journals and provide a ready source of high-quality information to guide the practitioner in selecting assessment and treatment techniques. Likewise, systematic reviews and meta-analyses provide scientific rigor to the summarizing of treatment outcome studies. Moreover, independent groups from government or government agencies have provided external scrutiny of the field, such as the National Institutes of Health (U.S.) and the National Institute for Health and Clinical Excellence (UK). The systematization of the sleep disorders, and greater consistency in approaches to assessment and management, has been aided by the development of a specific International Classification of Sleep Disorders system, currently in its second version (ICSD-2). Somewhat in parallel, the American Psychiatric Association work groups have produced several insomnia classifications over the years, with DSM-5 due for publication soon.
In all these ways, sleep seems to be an area of fast-developing interest. Needless to say, improvements in assessment and treatment services are hugely popular amongst patients who have often felt that their sleep problems and their impact on day-to-day life have been largely neglected by health-care systems. Slowly but surely this is changing. The growth of sleep centers in the U.S. first began in the 1960s; however, it has to be said that sleep services remain patchy across disorders and patchy around the world. For example, services for people with persistent insomnia or insomnia associated with psychiatric or medical disorders are generally poorer than those for sleep apnea and narcolepsy. Nevertheless, the scale of the insomnia challenge at community and primary care levels has been identified, and consideration has been given to the use of a “stepped-care” model to meet these needs (Espie). There is growing awareness too of restless legs syndrome and of periodic limb movement disorder, whereas the parasomnias, particularly non-REM parasomnias (such as sleepwalking and night terrors), are probably under-diagnosed and under-treated. It is striking that in this latter area, for example, there is very little evidence of what treatments actually work.
Aims and scope of this handbook
Having considered some of the historical landmarks in the field of sleep research and practice, and having also outlined some aspects of its current status, we hope that we have persuaded you of the timeliness of producing this handbook. Our vision has been to compile a resource that will meet the needs of psychologists in particular, but also other professionals who have an interest in sleep and sleep disorders. To achieve this, we are thrilled that each chapter in the handbook is authored by eminent international figures. If the handbook works as a source of educational, clinical, and indeed inspirational material, it is largely to their credit.
The handbook is divided into three main sections: Section I: Sleep; Section II: Sleep Disorders; and Section III: Sleep and Special Populations.
In Section I on Sleep, there is a total of 14 chapters exploring the nature and functions of sleep, from individual through societal perspectives. Philippe Peigneux’s chapter sleep and the brain is followed by chapters on the regulation of human sleep and wakefulness (Derk-Jan Dijk) and on the functions of sleep (Yvonne Harrison). Having provided this platform for an understanding of sleep itself in Chapters 1–3, this first section then pursues the relationships between sleep and human development (Kathryn Lee); sleep and human performance (Tim Monk); sleep, cognition, and cognitive neuroscience (Matt Walker); sleep and emotion (Martica Hall); and sleep and dreaming (Joseph de Koninck) in Chapters 4–8. Particular consideration is then given in Allison Harvey’s Chapter 9 to sleep and psychopathology, followed by Chapter 10 on sleep and psychotropic drugs by Dieter Riemann. Section I concludes with Chapters 11–14 devoted to societal aspects of sleep (Sara Arber), sleep and public health/safety (Torbjorn Akerstedt), and consideration of gender factors in sleep (Helen Driver). The closing chapter by Jason Ellis considers the relationship between sleep and the psychology curriculum for university education.
(p. 7) Section II on Sleep Disorders comprises a further 18 chapters divided into two subsections. Chapters 15–19 consider the epidemiology, classification, and assessment of sleep disorders. Epidemiology is covered by Kevin Morgan, with further chapters providing a socioeconomic perspective on sleep (Damien Leger), consideration of forensic aspects of sleep disorders (Rosalind Cartwright), classification and diagnosis (Jack Edinger), and clinical assessment techniques (James Wyatt). There then follows 13 chapters on the sleep–wake disorders. The first three of these are on insomnia, etiology, and conceptualization (Michael Perlis); behavioral and physiological assessment (Celine Bastien); and insomnia therapeutic approaches (Ken Lichstein). Chapters 23 and 24 are on sleep and psychiatric disorders (Rachel Manber) and sleep and medical disorders (Leanne Fleming and Judith Davidson), respectively. Sleep and substance abuse is covered by Todd Arnedt, and two chapters are devoted to parasomnias: the first is on nightmares (Anne Germain) and the second on night terrors and somnambulism (Anthony Zadra). In Chapters 28–30, circadian rhythm disorders are described by Leon Lack (phase-advanced and phase-delayed syndromes) by Annie Vallieres (shift work), and by Tracey Sletten and Jo Arendt (jet lag). In Chapter 31, Terri Weaver explores sleep-related breathing disorders, followed by Yves Dauvillier’s overview of hypersomnia and narcolepsy and Richard Allen’s chapter on restless legs syndrome and periodic limb movement disorder.
The handbook concludes with Section III on Sleep and Special Populations. Over the course of Chapters 34–39, expert information is provided on sleep-related problems in childhood (Jodi Mindell), in adolescence (Amy Wolfson), in older adults (Sonia Ancoli-Israel), in people with learning disability (Luci Wiggs), in people with brain injury (Marie-Christine Ouellet), and in people experiencing chronic pain (Michael Smith).
Thirty or forty years ago the importance of diet and exercise to health and well-being was barely acknowledged in mainstream science or clinical practice. At some level everyone knew of their importance, but they were lifestyle factors, lifestyle choices, were they not? How much has changed since then! Now they are major health policy drivers and cost headings. Their influence on health and health outcomes is highlighted on every medical and health professional course, they are routinely measured by various indices, and they are actively promoted and their adverse consequences treated in every community and on every hospital campus.
So the story goes for sleep, and sleep’s time has come!
From the ancient to the present day, the importance of sleep has seldom been disputed, but it has never had top billing. It seems that the combined critical mass of research, the needs of the population, and the shifting weight of professional interest is now pushing sleep onto center stage.
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