Sleep-related breathing disorders are a group of conditions characterized by disordered ventilation during sleep. The two major types are: central sleep apnea (CSA) and obstructive sleep apnea (OSA). While CSA is characterized by an absence of ventilatory effort, OSA describes a disorder of repeated mechanical obstruction of the airway.
Clinically, patients with OSA usually present with both nocturnal and daytime symptoms. Snoring between apneas is typically reported by bed partners are witnessed episodes of gasping or choking and frequent movements that disrupt sleep. Most patients awaken in the morning feeling tired and unrefreshed regardless of the duration of their time in bed. Consequently, excessive daytime sleepiness becomes a major daytime complaint. With extreme sleepiness, the patient may fall asleep while conversing, eating, walking or driving. Daytime symptoms also include headaches, impaired concentration, cognitive deficits, and increased irritability. As a result, the patient's quality of life can be adversely affected.
Insomnia is one of the most frequent sleep complaints: population surveys estimate one-third of all adults have one or more episodes each year. Insomnia complaints typically include difficulty initiating and/or maintaining sleep, and extended periods of nocturnal wakefulness and/or insufficient amounts of nocturnal sleep usually accompany these complaints. In addition to nighttime restlessness, insomnia also leads to daytime sequelae, including depressed mood, anxiety, daytime fatigue, irritability, reduced concentration and memory complaints. Daytime functioning impairment often results in low quality of life and difficulty with relationships and work.
In the U.S. population, the prevalence of insomnia is 10% to 15%. Women are 1.4 times more likely than men to report insomnia, and the prevalence of insomnia is also greater in the elderly population and in patients with chronic medical conditions. Psychiatric illnesses are more highly associated with insomnia than any other medical disorder, and epidemiologic studies of the general population show that one third to half of the patients with insomnia meet the criteria for primary psychiatric disorders, especially mood and anxiety disorders.
Excessive daytime sleepiness (EDS) predisposes an individual to developing serious performance decrements in multiple areas of social function, as well as to potentially life-threatening domestic, work-related, and driving accidents. The hypersomnia disorders are those in which EDS is the primary complaint and the cause is not disturbed nocturnal sleep or misaligned circadian rhythms. The three major types of hypersomnias are: narcolepsy (with or without cataplexy), idiopathic hypersomnia (with or without long sleep time) and recurrent hypersomnia.
Parasomnias are undesirable physical events or sensory experiences that occur during entry into sleep, within sleep, or during arousals from sleep. These events may include abnormal sleep-related movements, behaviors, emotions, dreaming, and autonomic activity. They are usually manifestations of central nervous system activation transmitted into skeletal muscle and autonomic nervous system. The most common explanation for parasomnias is that sleep and wakefulness are not mutually exclusive states and the overlap or intrusion of these states into one another causes these abnormalities. Parasomnias often occur in conjunction with other sleep disorders and it is not uncommon for several parasomnias to occur in a single patient.
There are two major types of parasomnias: non-rapid eye movement (NREM) and rapid eye movement (REM) parasomnias.
Circadian (from the Latin for about a day) rhythms are present in almost all eukaryotic organisms from single-celled algae to humans. It is an internal timing system that allows animals to keep time in the absence of external environmental cues, the strongest of which is light. From an evolutionary point of view, circadian rhythms are crucial in allowing animals to anticipate and synchronize brain and body functions so they occur at optimal times with the external world. Many physiologic variables demonstrate endogenous circadian rhythms, including heart rate, blood pressure, blood glucose levels, hormone secretion, brain metabolism, psychomotor performance and, of course, sleep propensity.
For optimal sleep, the desired sleep time should match the timing of the circadian rhythm of sleep and wake propensity. In circadian rhythm sleep disorders (CRSD), there is a persistent or recurrent misalignment between the patient's sleep pattern and the pattern that is desired or regarded as the societal norm. The patient cannot sleep when sleep is needed or expected. The wake episodes can occur at undesired times as a result of sleep episodes that occur at inappropriate times; therefore, the patient may complain of insomnia or excessive sleepiness. While the exact pathophysiology of CRSD is unknown, there is almost certainly an abnormal interaction between the endogenous circadian rhythm and the sleep homeostatic process that regulates sleep and wakefulness.
There are six major types of circadian rhythm sleep disorder: advanced sleep phase, delayed sleep phase, irregular sleep-wake, free-running, jet lag and shift work.
Restless legs syndrome (RLS) is the most common type of sleep related movement disorders, which also include periodic limb movement disorder (PLMD), sleep related leg cramps, sleep related bruxisms and sleep related rhythmic movement disorder.
RLS is a sensorimotor disorder characterized by a strong, nearly irresistible urge to move the legs. Patients describe a building of uncomfortable sensation to a point where they must give in and move their legs. Typical symptoms involve the ankle and the knee, but in severe cases the thighs or feet, and rarely the arms, can also become involved. The symptoms are typically bilateral. RLS tends to become more pronounced during times of prolong inactivity and it has a circadian tendency for symptoms to be maximal in the evening, increasing in intensity toward the early sleep period. Consequently, RLS may cause insomnia and prolonged awakenings, leading to significantly reduced total sleep time.
For more information on sleep, please visit the following websites:
