Developing the classification scope of sleep disorders helps to identify possible causes, differential diagnosis and subsequently proper management. This essays aim at providing a brief yet a comprehensive review on the types, causes, and common treatments of sleep disorders.
Sleep and wakefulness are two phases of brain activity, which are separate physiologically and psychologically, although influenced by each other (Coleman, 1999). Sleep disorders point to changes in the quality (sleep-wake cycle or REM-Non REM cycles), circadian (rhythmic) pattern, or duration (amount) of sleep (Kumar, 2008). The aim of this essay is to provide a brief yet a comprehensive review of sleep disorders about types, causes, and different treatment outlines.
Types and causes of sleep disorders
In 2001 the American Academy of Sleep Medicine (in association with the European, Japanese, and Latin American Sleep Research societies) published the Revised International Classification of Sleep Disorders Diagnostic and Coding Manual. In this document, sleep disorders were classified into four main categories, dyssomnias, parasominas, sleep disorders associated with mental, neurological, or other medical disorders, and proposed sleep disorders.
These are sleep disorders that produce insomnia (difficulty to instigate or maintain sleep) or excessive sleepiness. Dyssomnias are further classified into three disorders categories (American Academy of Sleep Medicine, 2001):
Intrinsic sleep disorders: These disorders arise within the body. External factors may influence them, but are able to do so only because an internal abnormality exists within the body. They include excessive sleepiness syndromes (narcolepsy, and hypersomnia); difficulty in initiating sleep (insomnia), sleep related breathing disorders (sleep apneas), and abnormal limb movements (American Academy of Sleep Medicine, 2001).
Sleep apneas: It is cessation of breath during sleep and is further classified into three types. Obstructive sleep apnea where upper airway obstruction causes apnea, despite the presence of respiratory efforts. This creates a negative intrapharyngeal pressure that leads to pharyngeal collapse during sleep. Characteristically patients snore loudly, have short periods of arousals resulting from interrupted breathing. It affects males more commonly and increases with age. Central sleep apnea is characterized by periods of absent respiratory efforts resulting in absent airflow during sleep. It may result from lesions that affect the sensory component of the complex array of feedback loops and reflexes that monitor the demand of the patient and adapt respiration to meet metabolic needs (as in Ondine’s curse, and familial dysautonomia or Riley-Day syndrome). It may also follow defects involving the integrative and executive neurons (as in acquired central hypoventilation during sleep). Alternatively, it may result from impairment of the motor component of respiratory reflexes as in amyotrophic lateral sclerosis or myasthenia gravis. Finally, central sleep apnea may be secondary to non neurological causes as in chronic obstructive airway disease. Mixed sleep apnea is a condition where there are obstructive and central episodes of apnea during sleep. It is believed to be a separate entity of sleep apnea rather than a combination of obstructive and central sleep apnea disorders (Kryger, Roth, and Dement, 2000).
Insomnia: It is the inability to instigate sleep that is of enough duration to provide a sense of being refreshed the next day. It may be mild, moderate, or severe according to the associated impairment of social and-or occupational performance. Some insomnia may be constitutional and transient insomnia for few days is common to healthy individuals undergoing stressful conditions. Long-term insomnia is a risk factor for developing psychiatric conditions as depression or substance abuse. It can be secondary to medical painful condition (as duodenal ulcer, and arthritis) (Kumar, 2008).
Narcolepsy: It is a neurological disorder where patients fall asleep during the day despite having satisfactory sleep amount the previous day. It differs from sleep apneas in that naps are short and refreshing, and patients are alert on awakening. Patients usually do not snore and are not morbidly obese. There are associated symptoms as cataplexy, hypnagogic hallucinations, and partial to total paralysis of skeletal muscles at sleep onset (sleep paralysis) (Kamal, 2004).
Extrinsic dyssomnias: These are disorders that arise because of factors outside the body. Removal or correction o these factors results in resolving such sleep disorders. There may be internal factors that help to develop or maintain such disorders but that do not produce a sleep disorder without the external factor being present. Extrinsic dyssomnias include those caused by poor sleep habits, disruptive environmental influences and acute stress and conflicts (American Academy of Sleep Medicine, 2001).
Circadian rhythm disorders: These are sleep disorders related to the timing of sleep within the 24 hours day. Sleep-wake cycle (circadian rhythm) disorders can be secondary to environmental effect on the biological clock or can be primary where there is malfunction of the biological clock (Kumar, 2008). Delayed sleep phase, and advanced sleep phase syndromes (DSPS and ASPS) are the commonest primary circadian rhythm (sleep-wake cycle) disorders. The difference between the two conditions is in the sleep-wake timing, in DSPS, the patient falls asleep and rises late, while in ASPS, the patient falls asleep and rises earlier than wished. Genetic studies identified specific genes associated with both conditions. Other circadian rhythm disorders include free-running disorder and irregular sleep-wake rhythm (Sack and others, 2007).
These are disorders that interfere with the sleep process rather than being primary sleep disorders. They are the result of central nervous system activation usually of the skeletal muscles or the autonomic nervous system resulting in disorders of arousal, partial arousal, and sleep stage transition. They are classified according to the different patterns of movements and behaviors occurring during sleep into four groups (American Academy of Sleep Medicine, 2001).
First, arousal disorders (disorders of the normal arousal mechanisms) typically observed in non-REM sleep (as sleepwalking and night terrors). Second, sleep-wake transition disorders, which occur in either direction (sleep to wakefulness or the opposite) as in sleep talking and hypnic jerks. Third, Parasomnias can be related to REM sleep as in REM sleep behavior disorders where the sleeper acts out dreams. Other Parasomnias include bruxism and enuresis (American Academy of Sleep Medicine, 2001).
Sleep disorders associated with mental, neurological or other medical disorders
These are sleep disorders that occur in association with of the mentioned conditions, or iatrogenic because of drug administration or drug withdrawal (Kamal, 2004).
Drugs and sleep: Many pharmacological therapies have displayed promising results treating some sleep disorders. Other common drugs can precipitate a sleep disorder either during administration or withdrawal. Anticholinergics may cause REM latency and affect non-REM sleep during drug administration. Anticonvulsant carbamazepine results in REM latency and affects REM sleep percentage, while increases daytime sleepiness during drug administration and withdrawal. Some antidepressants (as trazodone) have a complex effect on sleep architecture. Trazodone cause REM latency, increase daytime sleepiness, and affects sleep continuity during drug administration, while affects REM percentage during withdrawal. Antihypertensive drug atenolol affects both REM and non-REM percentages during administration, it also affects daytime sleepiness, and total sleep duration. It increases REM latency during administration and withdrawal. Antihistaminic diphenhydramine increases daytime sleepiness during administration, while alcohol affects sleep latency and REM percentage during withdrawal and increases daytime sleepiness, REM latency, and total sleep time during administration (Kamal, 2004).
Stress and sleep disorders: Cross-sectional studies show that stress relates to impaired sleep. It is associated with shortened sleep, possibly with reduction in sleep stages 3, and 4, and sleep fragmentation. A circle results because disturbed sleep increases stress markers levels specially cortisol, which augments the effects of stress (Akerstedt, 2006). Evidence shows that neurotransmitters (acetylcholine and GABA among others) play a key role in disturbing sleep pattern secondary to psychological stress. In addition, the hypothalamic-pituitary-adrenal axis influences sleep pattern in response to psychological stress conditions (Cui and others, 2008).
Depression and sleep disorders: Depression is the commonest mood disorder and is usually associated with sleep disorders in the form of insomnia or hypersomnia. In patients with recurrent depression episodes, sleep disorders often appears before low mood and sense of dissatisfaction. Depressive patients show increased sleep latency, REM sleep is affected in many ways, and there is shortened REM sleep latency, increased first REM period density and sleep onset REM period (Sloan, 2006, and American Academy of Sleep Medicine, 2001).
Proposed sleep disorders
These disorders are not sufficiently described as their existence as distinct sleep disorders is still to be proved. They may be only recently described (sleep-related laryngospasm), difficult to characterize (menopause related sleep insomnia), or normal variation or extremes (short and long sleepers, and sleep disturbances in the aged) (American Academy of Sleep Medicine, 2001).
Aging and sleep disorders: Sleep amount , pattern, and quality change in aged individuals, total sleep time decreases, however, the time spent in bed increases. They show increased sleep latency with frequent awakenings at night. There is a decrease in stages 3 and 4 of non-REM sleep, and by the age of 60 they may disappear. The first sleep cycle (mainly stage 4) decrease accordingly with increasing age. The proportion of REM sleep decreases rapidly by the age of 70 and does not increase with each sleep cycle (in contrast to young adults). REM sleep period become increasingly dispersed among periods of stage 2 non-REM sleep. Besides, primary snoring becomes commoner in the elderly, and usually occurs in isolation of sleep apnea possibly because of increased flaccidity of the upper airway dilator muscles. Many factors add to the problem in the elderly, the absence of the organizing influence of employment and marriage on the sleep-wake cycle, impaired capacity to maintain sleep. Geriatric diseases (Parkinson’s disease, diabetes, hypertension, heart diseases), and medications taken (antihypertensive, muscle relaxants, and sedative) all contribute to aggravate sleep disorders in the elderly (Jagus and Benbow, 1999).
Menopause related insomnia: It is one of the menstrual associated sleep disorders, whose main feature is the presence of repeated night awakenings associated with menopausal hot flashes or night sweating. Sleep onset disturbance may also occur, although not a common feature. The key to identify this problem is the presence of other manifestations of menopausal condition and hormonal assay (American Academy of Sleep Medicine, 2001).
Snoring: It is an inspiration sound produced by vibration of the soft parts of the oropharyngeal cavity during sleep. It can be mild, moderate, or severe based on its frequency and degree of disturbance to other (bed partner or family members). The pathological importance of snoring relates to its volume, timing, and the duration of total sleep duration occupied by snoring (Kamal, 2004).
Treatment of sleep disorders
Medications for sleep disorders: The aim of using drugs in treating sleep disorders is to limit it use to relieve severe disorders while directing the behavioral and medical treatment to relieve the cause of the disorder. Patients should understand that it may a long duration of treatment to correct the condition, thus patient education is an important adjunct (Wagner and Wincor, 2006). Benzodiazepines are used to treat insomnia; however, withdrawal may affect the REM sleep. Zaleplon and zolpedim are effective alternatives, yet with no undesirable withdrawal effects. Sedating antihistamines and sedating antidepressants may be used in treating insomnia. Amphetamines can be used to increase daytime alertness, and dopamine agonists are used to treat restless leg syndrome and periodic limb movements. Medroxyprogesterone acetate, tricyclic antidepressants, and acetazolamide have been used with success to manage central sleep apnea (Pagel and Parnes, 2001).
Sleep apnea treatment: Treatment of obstructive sleep apnea can be surgical in selected cases. Procedures to relieve upper airway obstruction as uvulopalatoplasty are indicated in snorer non apneic or in mild cases of obstructive sleep apnea. Other procedure to correct or widen the upper airway may be indicated in some cases, however long term results of surgical treatment are uncertain (Kamal, 2004). Patients with mild to moderate obstructive sleep apnea (OSA) are advised to use oral appliances as they are more tolerable than CPAP therapy. However for patients with severe OSA or with central sleep apnea, CPAP therapy is always advised (Kushida and others, 2006).
Management of overweight to treat sleep apnea: Morgenthaler and others (2006) reviewed the literature about weight reduction (and other therapies) to correct sleep apnea. They inferred successful dietary weight reduction helps to improve disorder parameters in patients with OSA. However, it should combined with primary treatment of the condition whether oral appliances, CPAP, or surgery and in this context, bariatric may be a helpful adjunct treatment. Nevertheless, their review showed there is little evidence based data to suggest a guideline conclusion, and organized targeted weight loss program to manage apnea cases (whether as a single or combined therapy) still lacks evidence.
Management of stress to control sleep disorders: Stress is the way an individual reacts, physically and emotionally, to daily events. Glass, 2008 describes how to manage stress to achieve better sleep. The first step is to assess what is stressful, once it (a stressor) is identified, it can be faced and managed. Second one should not hesitate to get social support from family and friends and psychological support which might be helpful to achieve good quality sleep. Exercise and healthy food can be helpful to blow off the stream and supply energy needed besides keeping healthy and fit helps in reducing stress. One should free up some time for rest and leisure even on the expense of handing over some responsibilities.
Sleep disorders cover a wide range of interrelated medical, neurological and psychological diseases. There are more than 100 identified sleep disorders that can be grouped in four categories, dyssomnias, parasomnias, sleep disorders associated with mental, neurological, or other medical disorders, and proposed sleep disorders. However it is not possible to identify all causes of all sleep disorders, although research has provided many explanations. Undiagnosed and consequently untreated sleep disorders have their impact on the patient’s health as well as have their socioeconomic impact. If one thing to be concluded, it is patients’ education is essential for understanding, cooperation, and management of sleep disorders.
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