Contemporary Sleep Medicine For Patients

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Sleep takes up one third of the human life and has always been a subject of fascination for human beings. In the past century, significant progress has been made in the study of sleep.

Sleep is defined as a reversible state of decreased responsiveness to the environment. It has been historically thought to be a passive state of inactivity; however, electrical recordings of brain waves have shown that the brain remains very active during sleep, but that this activity is distinctively different from the wake state.

Sleep is divided into two main states, non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. The latter is thought to be the state where the most vivid dreams occur. Different brain regions and groups of neurons in the brain are responsible for the generation of each of these two states. Human fetuses have been shown to display sleep brain waves as early as 28 weeks of gestation.

The question of “why do we sleep?” has been occupying scientists for some time and a clear answer has yet to be accepted by all. Many hypotheses exist. The evolutionary adaptation hypothesis claims that sleep evolved to protect the organism by making it quiescent during times where activity would be dangerous (exposure to predators or injury), while also saving energy during those times. More recent evidence suggests that, during sleep, the brain regenerates energy that has been depleted by wakefulness. Other studies also suggest that sleep enhances learning and memory formation.

Based on the National Sleep Foundation Sleep in America polls, which encompassed snapshots of sleep habits and symptoms, the number of people reporting sleep problems is increasing. Over a span of 8 years, the percentage of Americans sleeping less than 6 hours per night went up to 1/5 of the population, and those who reported sleeping 8 hours or more dropped to approximately 1/4 of the population. More than half of people reported experiencing a sleep problem at least a few nights in week, with 4 out of 10 reporting problems every night. However, only 1/3 of all adults have ever discussed sleep with a healthcare professional; when they seek medical advice, almost half of them are found with a sleep disorder.

Seeing a physician for the first time for a sleep complaint can be a daunting process. Invariably, the physician will need to perform a detailed history and physical examination as part of a standard diagnostic evaluation. The most common reasons for which patients seek an evaluation with a sleep specialist include snoring, excessive daytime sleepiness, insomnia (defined as difficulty with initiating or maintaining sleep) and abnormal nocturnal behaviors or sensations. Each of these presented symptoms will be briefly addressed, with specific attention to the diagnoses that the doctor may consider and the kinds of questions you will likely to asked during the evaluation process.

The phenomenon of sleep has captured the imagination of humans for centuries. For a lay person with no particular knowledge of sleep pathophysiology, “sleep study” often implies what is known to the specialists as nocturnal polysomnogram or PSG. Although this is true in the vast majority of the times, sleep study is not limited to nocturnal polysomnogram but also includes many other sophisticated tests, such as Multiple Sleep latency Test (MSLT), Maintenance of Wakefulness Test (MWT), etc. The technology to measure various physiological parameters has evolved over the years and today the methodology used for conducting various sleep studies is perhaps one of the most sophisticated in the medical sciences. Depending on the nature of symptoms, the physicians may order different tests to make the diagnosis and/or treat various sleep disorders. In addition, to the various in-lab sleep studies, other diagnostic tests that may be used in the diagnosis of sleep disorders include home sleep monitoring, actigraphy, etc.

Snoring is the sound of soft tissues vibrating within the upper throat during sleep. The vibration is a result of turbulent air flow through the throat as it narrows during sleep. Snoring is very common in adults and may occur alone or be a feature of other conditions characterized by greater throat narrowing during sleep, namely upper airway resistance syndrome (UARS) and obstructive sleep apnea syndrome (OSA). UARS is marked by daytime sleepiness and/or fatigue in the context of frequent respiratory-effort related arousals (RERAs). RERAs are episodic arousals that follow periods of more intense breathing effort as resistance to airflow in the throat increases. Once the throat is very narrow, hypopneas (partial reduction in airflow) and apneas (complete cessation of airflow) occur, and these events comprise OSA. Whether UARS is an entity distinct from OSA remains still debated.

Risk factors for snoring and UARS are similar and include obesity, nasal congestion, alcohol and drug consumption before bed, and abnormalities of the bony and soft tissue structures of the head and neck. Snoring can be a nuisance, but generally does not produce daytime sequelae, while UARS may lead to daytime fatigue and sleepiness. Treatment options for snoring and UARS include risk factor modifications, nasal-directed therapies, oral appliances, upper airway surgery, while continuous positive airway pressure (CPAP) is an additional option for UARS.

The word “apnea” means literally "without breath", and thus “sleep apnea” means not breathing while sleeping. Normally, during sleep we do not have pauses in-between breaths. Individuals with sleep apnea often stop breathing completely (apnea) or partially (hypopnea) during sleep for 10 seconds or more and sometimes for more than one minute, which leads to low oxygen in the brain and other organs. Sleep apnea is, therefore, a chronic condition where the normal sleep respiratory cycle is disrupted.

Approximately 25% of adults seem to have sleep apnea of some degree. Men seem to be more commonly affected than women (especially pre-menopausal women). Other risk factors include: older age, overweight or obesity, and having a small mouth, jaw or throat, large tongue or retro-position of the lower jaw. Smoking, alcohol, ingestion of sedative medications, chronic nasal inflammation (rhinitis) with obstruction, large neck girth, etc represent risk factors for this disorder.

Sleep apnea can be treated by applying continuous positive airway pressure (CPAP), dental appliances or surgery. The decision to treat and with what specific modality is dependent on a complex interplay of symptoms, co-existent disorders and disease severity. This decision should be made by the patient in conjunction with the healthcare provider, preferably a specialist in Sleep Medicine who has enough experience in diagnosing and treating this condition.

Central sleep apnea is not a single disorder. Rather, the term includes several conditions that have, in common, similar clinical presentations and sleep study findings. Central sleep apnea is characterized by repetitive pauses in breathing due to either an absence or reduction in respiratory effort. Diagnosis of central sleep apnea is determined using sleep studies. The selection of treatment depends on the underlying cause, and may include the use of oxygen supplementation, drug therapy or positive airway pressure.

Obesity Hypoventilation syndrome (OHS) is defined as the triad of obesity, daytime carbon dioxide accumulation (hypoventilation), and sleep disordered breathing in the absence of an alternative explanation. Patients with obstructive sleep apnea (OSA), those who are more obese and have more severe OSA are more likely to have the syndrome. It is unclear why some patients with OSA develop OHS and others do not. It is important to identify the syndrome early, as these patients may have a significantly increased risk of dying if left untreated. The authors describe current understanding of the pathogenesis of the disorder and optimal treatment modalities.

Insomnia is a common condition. People with insomnia complain of difficulty falling asleep, difficulty in maintaining sleep, or light, non-restorative sleep. Daytime symptoms include fatigue, attention and memory difficulties, and irritability. Difficulty sleeping at night is associated with a disturbance in physiological mechanisms that are involved in regulation of sleep. Such a disturbance may be a result of a genetic/dispositional issue. A disturbance may also be produced by a stressful life event, or jetlag, or an illness. Behavioral patterns and attitudes toward sleep may also disturb sleep mechanisms. Often a combination of dispositional, situational and behavioral factors is responsible for insomnia. Various treatment techniques are available that are designed to strengthen sleep mechanisms. These techniques actively engage the person to implement behavioral and cognitive changes that promote healthy sleep.

Circadian rhythm sleep disorders are a group of disorders in which the individual's sleep is misaligned with the normal sleep and wake times. This is due to lack of synchrony between the body circadian clock timekeeping mechanism and the 24-hour day-night cycle. Some of the disorders such as delayed sleep phase disorder, advanced sleep phase disorder, free running disorder, and irregular sleep wake rhythm disorder are due to abnormalities in the circadian clock timekeeping mechanism. There are other disorders such as shift work disorder and jet lag disorder in which the circadian clock timekeeping mechanism is normal but the problems arise due to mismatch caused by extrinsic factors (night or early morning shift work and air travel across multiple time zones). Proper recognition and treatment of these disorders are necessary to ameliorate the symptoms and minimize the adverse social and occupational impact.

Narcolepsy is a sleep disorder characterized by sleepiness (sleep attacks, need to nap during the day), cataplexy (being weak or paralyzed when laughing, angry or during sudden emotions) and disturbed sleep (insomnia, vivid dreaming, being paralyzed but awake when waking up). Not all patients have all symptoms. When cataplexy is present, the disorder is almost always due to a destruction by the immune system of about 70,000 brain cells that produce a chemical called hypocretin. As this chemical helps in staying awake and regulating sleep and muscle tone, the lack of hypocretin explains all the symptoms of narcolepsy. In these cases of narcolepsy, the disease is life-long and does not resolve. When cataplexy is not present, many causes may be involved and the diagnosis is more difficult. Evolution and response to treatment are also more variable. Narcolepsy is diagnosed using sleep tests, biochemical measures and occasionally by measuring hypocretin in the cerebrospinal fluid (CSF) after a lumbar puncture. Current treatments involve medication and behavioral, life styles changes.

Idiopathic hypersomnia is an uncommon disorder, but it is serious and needs attention. It is very disabling to patients and can result in motor vehicle accident, difficulty with school or maintaining a job. It can also place stress on families or relationships. It is usually diagnosed by excluding other disorders causing similar symptoms. Individuals with this disorder often sleep for long periods during the night and in addition may nap for prolonged periods during the day and despite all this sleep they continue to display daytime sleepiness. The cause of this disorder is unknown. It seems most people have this problem lifelong but there are instances when people have spontaneous improvement [1]. The typical approach is to modify lifestyle and use medications to help with daytime alertness.

Sleep-related movement disorders represent an array of phenomena characterized by abnormal movements during or just preceding sleep. The majority of sleep-related movement disorders is represented by benign conditions which have no known adverse effects on health. Many of these disorders include muscular jerking of the torso or legs. Some disorders consist of repetitive movement of the legs. The severity of each of these disorders varies greatly and, in severe forms, the sleep-related movement disorders can result in sleep disruption and daytime sleepiness. Importantly, similar movements can arise from disease of muscle, nerve, spinal cord or even brain, so if movement is frequent or severe, it is best to consult a health care professional.

The term “parasomnia” is derived from Greek word para meaning “alongside” and the Latin word somnus meaning “sleep”. Parasomnias are any undesirable physical events or experiences that happen during falling asleep, staying asleep or during arousals from sleep. The disorders within the category of parasomnias vary from transient and relatively benign events such as occasional episodes of sleep walking or nightmares to potentially injurious and sometimes life-threatening events, with potential medico-legal consequences, such as REM sleep behavior disorder. Parasomnias are also considered to be automatisms since the subjects do not have any conscious awareness during the episodes. Parasomnias can significantly affect the quality of sleep of the patients, and also of the bed-partners. For a clinical diagnosis, a thorough clinical assessment, appropriate tests (where indicated) and judicious use of medications can help in the vast majority of patients with parasomnia disorders.

Modern advances in science and technology have resulted in a steady increase in life expectancy of human beings, especially in developed countries. In the United States, the current average life expectancy at birth is 80 years for females and 75 years for males. At age 65, the current average life expectancy is 20 years for females and 17 years for males [1]. This trend implies a gradual increase in the proportion of older adults in the general population, and that the elderly will account for an increasing and significant proportion of patients seen by physicians in most clinical disciplines. For this reason, understanding the aging process and the associated changes in different organs and systems is of paramount importance. In addition, older adults themselves should be aware of normal age-related changes (changes in their functional status that is the result of aging per se), and changes that are consequences of conditions (diseases, effect of medications) that adversely affect their health or functional status. Knowledge of these potentially reversible factors would empower older adults, and enable them to interact with their health care providers and participate in decision making process.

“Successful aging” is one term used to describe the impact of aging on an individual. In general, the term implies absence of disease-related disability, good physical and mental activity and active engagement in daily life activities [2]. Sleep-related factors have been shown to be significantly associated with measures that indicate successful aging. In the next sections, we will discuss changes in sleep that are observed among otherwise healthy older adults (considered to be changes that are the results of normal aging), as well as sleep disorders that are commonly encountered among older adults.

Sleep is essential for optimal mental, physical and social wellbeing (or, generically, health). Sleep disruption and/or deprivation can have adverse health consequences, promoting or worsening cardiovascular disease and diabetes. Sleep-wake regulation depends on complex interactions between multiple brain regions. Many medications can have direct or indirect effects on these sleep-wake regulation regions and thus may promote sleepiness, insomnia or sleep disruption. We will review briefly the impact of commonly used medications on the sleep-wake cycle.

Over the past decade, more and more evidence has been emerging to link cardiovascular diseases and sleep. The most notorious association has been with obstructive sleep apnea (OSA). Indeed, OSA has been linked to a greater risk of elevated blood pressure, heart attacks, heart failure, abnormal heart rhythm and strokes. The low oxygen levels that occur during sleep in patients with OSA are thought to be responsible for most of the cardiovascular consequences. Treatment with CPAP has been shown to improve blood pressure and reduce mortality from heart attacks but long term studies are still lacking. Central sleep apnea, another sleep disorder, is linked to congestive heart failure and may also signal increased mortality. CPAP treatment is promising. Other sleep disorders such as insomnia, long and short sleep time, restless leg syndrome and circadian rhythm disorders have also been associated with higher cardiovascular risk.

In our fast-paced world, sleep frequently becomes a casualty of the “24/7 model” of the society. Obesity, diabetes and heart disease epidemics seem to go hand in hand with significant and persistent alterations in human metabolism.

Clinical studies have shown that people who sleep less than 6 hours or more than 8 hours a day are often overweight or obese. Obesity has become, at least in the western society, a very common condition. There is a strong connection between sleep apnea and obesity, diabetes and heart disease. In fact, we now know that individuals with untreated sleep apnea are at a greater risk of heart attacks, strokes, development of diabetes and/or hypertension.

Metabolic syndrome (MetS) is defined very differently in the literature, but seems to be defined most of the time by a constellation of findings such as central (abdominal) obesity, diabetes, impaired glucose tolerance or pre-diabetes, abnormally elevated lipids and/or other metabolic abnormalities which accompany what is called insulin resistance (IR). Given the obesity high frequency in the general population, the prevalence of MetS is, undoubtedly, on the rise.

When considered separately from cardiovascular disease, stroke is the third leading cause of death and ranks as the leading cause of long-term disability [1]. Strategies for stroke treatment and prevention have helped to reduce the burden of disease, but it remains an important public health challenge [2]. Therefore, understanding underlying causes of disease and developing novel therapeutic approaches for stroke is of crucial importance. Understanding the link between sleep apnea and stroke may represent one such novel approach.

There is a substantial amount of evidence linking sleep and epilepsy. In both adults and children with epilepsy, sleep and sleep deprivation can precipitate seizures. EEG recordings are more likely to reveal abnormalities during sleep than during the awake state. There are some types of epilepsy that are characterized by seizures arising exclusively during sleep or immediately upon awakening.

One of the most common complaints of people with epilepsy is daytime sleepiness or fatigue. Despite the potential impact of these complaints on a person's quality of life, little research has been done in this area. Sleepiness and fatigue are often attributing to the effects of seizures or ant-seizure medications. However, recent studies suggest that people with epilepsy may be at particular risk for sleep disorders, such as sleep apnea, which can also contribute to fatigue and daytime sleepiness. Furthermore, exciting preliminary data suggest that treating sleep problems may improve seizure control. As a result, people with epilepsy, particularly if seizures have continued despite appropriate treatment, should be evaluated for sleep disorders.

People with daytime sleepiness, difficulty falling or staying asleep, or breathing disturbances during sleep should consult their physician. An overnight sleep study (polysomnogram; PSG) sometimes combined with electroencephalography (EEG) can diagnose common sleep disorders such as sleep apnea.

Pediatric sleep disorders are quite common and often disturbing to either the patient or the child's family. As the patient matures into an adult, sleep disorders continue to be common and an important factor in development, both social and cognitive. Nonrestorative sleep can hamper a child's ability to concentrate and control emotions and behavior. Sleep disorders vary among age groups, but most can occur with varying frequency at any age.

Several disorders are typically seen only during the first few years of life, including colic, excessive nighttime feedings, and sleep onset association disorder. A number of conditions are common during childhood but begin to improve as the child ages. The non-REM sleep parasomnias, including sleepwalking, confusional arousals, and night terrors, are the most common in the pediatric category. Nightmares are also common in childhood but can occur at any age.

Sleep-related breathing disorders including obstructive sleep apnea, central sleep apnea, central alveolar hypoventilation syndrome, and Cheyne-Stokes respiration are not found only in adults but are, in fact, quite common in the pediatric population. While these disorders can occur at any age, treatment options vary substantially by age.