Occasionally, sleeping problems are due to sleep disorders rather than external factors. Anybody falling in this category has to see a sleep doctor if the symptoms are severe and don’t go away by themselves. Here is a description of the most common disorders:

Excessive Daytime Somnolence (EDS)

Excessive somnolence is characterized by a lack of relief even after increasing the nighttime sleep duration, inability to concentrate and impaired cognition and motor skills. The onset of the disease is generally around age 15 to 30.

One variation of EDS is narcolepsy. In narcolepsy, the order and length of NREM and REM sleep periods are disturbed, with REM sleep occurring at sleep onset instead of after a period of NREM sleep. Night time sleep does not include as much deep sleep, so the brain tries to “catch up” during the day, hence EDS. The classic sleep attack is an irresistible desire to fall asleep in inappropriate circumstances and at inappropriate places (e.g., while talking, driving, eating, playing, walking, working, sitting, listening to lectures, watching television or movies, during sexual intercourse, or when involved in boring or monotonous circumstances). These spells last from a few minutes to as long as 20 to 30 min and the patient generally feels refreshed upon waking. There are wide variations in frequency of attacks, anywhere from daily, weekly, monthly or every few weeks to months. Attacks generally persist throughout the patient’s lifetime although fluctuations and rare temporary remissions may occur. Patients often show a decline in performance at school and work and encounter psychosocial and socio-economic difficulties as a result of sleep attacks and EDS. These sleep attacks are often accompanied by cataplexy (sudden loss of tone in all voluntary muscles except respiratory and ocular muscles). The attacks are triggered by emotional factors such as laughter, rage, or anger more than 95% of the time. Most commonly, the patient may momentarily exhibit buckling of the knees, head nodding, dropping of the jaw, dropping of objects from hands, dysarthria or loss of voice, and sometimes they may even slump or fall forward to the ground for a few seconds. The duration is usually a few seconds to minutes and consciousness is retained completely during the attack. Generally, cataplectic spells occur months to years after the onset of sleep attacks, but occasionally cataplexy is the initial manifestation. It is a life-long condition, but it generally is less severe and may even disappear in old age. Sleep paralysis, hypnagogic hallucinations, disturbed night sleep and automatic behavior are the other manifestations of the narcolepsy-cataplexy syndrome. Symptomatic or secondary narcolepsy-cataplexy may result from diencephalic and midbrain tumors, multiple sclerosis, strokes, vascular malformations, encephalitis, cerebral trauma and the presence of cancer in the body.

A second variation of EDS is idiopathic hypersomnia (idiopathic means cause is unknown). The sleep pattern is different from that of narcolepsy in that the nocturnal sleep is not disturbed. The patient generally sleeps for hours but the sleep is not refreshing. This condition may be mistaken for sleep apnea. However, the patient does not have a history of physical weakness, snoring or repeated awakenings throughout the night. Some patients may have automatic behavior during the day and often forget what they have been doing throughout the day.

Insomnia

Insomniacs complain of difficulty initiating and maintaining sleep, including early morning awakening for at least 3-4 times per week, persisting for more than a month, and associated with an impairment of daytime function. Acute insomnia may be associated with an identifiable stressful situation. Most cases of insomnia are chronic and co-morbid with other conditions which include psychiatric, medical and neurological disorders or drug and alcohol abuse. In some cases, no cause is found. Insomnia patients may complain of some or all of the following: difficulty initiating or maintaining sleep, repeated awakenings or early morning awakenings, non-restorative sleep, daytime fatigue, lack of concentration, irritability, anxiety, depression, and muscle aches and pains. See also the page on insomnia.

Circadian Rhythm Sleep Disorder

Circadian rhythms are the natural cycles of wakefulness and sleep that the body progresses through. They are adjusted internally by the human body to the environment by external cues, the primary one of which is daylight. See section on stimulus control therapy.

Delayed sleep-phase syndrome (DSPS) is a chronic disorder of the timing of sleep, peak period of alertness, the core body temperature rhythm, hormonal and other daily rhythms, compared to the general population and relative to societal requirements. People with DSPS generally fall asleep some hours after midnight and have difficulty waking up in the morning. Often, people with the disorder report that they cannot sleep until early morning, but fall asleep at about the same time every “night”.

Advanced sleep phase syndrome (ASPS) is a condition in which patients feel very sleepy and go to bed early in the evening (e.g. 6:00–8:00 p.m.) and wake up very early in the morning (e.g. 1:00–3:00 a.m.). ASPS is more frequently encountered in the elderly and in post-menopausal women than in younger people.

Non-24-hour sleep-wake syndrome (Non-24) is a condition in which people do not have internal clocks that reset and stay balanced within a 24 hour schedule. In most cases, their circadian rhythms are set on longer loops, usually resulting in 25 or 26 hour cycles, or even more in some cases. For more on Non-24, see this page.

Irregular sleep-wake rhythm is a rare and serious form of circadian rhythm sleep disorder. It is characterized by numerous naps throughout the 24-hour period, no main nighttime sleep episode and irregularity from day to day. Sufferers have no pattern of when they are awake or asleep, may have poor quality sleep, and often may be very sleepy while they are awake. The total time asleep per 24 hours is normal for the person’s age.

Abnormal Movements Or Behaviors During Sleep

Restless legs syndrome (RLS) is the most common movement disorder. The sensory manifestations of RLS include intense disagreeable feelings which are described as creeping, crawling, tingling, burning, aching, cramping, knife-like or itching sensations. These sensations occur mostly between the knees and ankles causing an intense urge to move the limbs to relieve these feelings. Sometimes similar symptoms occur in arms or other parts of the body, particularly in advanced stages of the disease. At least 80% of RLS patients have periodic limb movement in sleep. The condition generally has a profound impact on sleep.

Sleepwalking is common in children between the ages of 5 and 12. Sometimes it persists into adulthood or rarely begins in adults. Sleepwalking begins with an abrupt onset of motor activity (the person gets out of bed and starts moving around) arising out of slow wave sleep during the first third of the sleep. Episodes generally last less than 10 minutes. There is a higher incidence in those with family history of sleepwalking. Injuries and violent activities have been reported during sleepwalking episodes, but generally individuals can negotiate their way around the room. Rarely, the occurrence of homicide has been reported and sometimes abnormal sexual behavior occurs. Sleep deprivation, fatigue, illness and sedative medicine can trigger sleepwalking.

Bruxism (tooth grinding) often occurs between ages 10 and 20, but it may persist throughout life, often leading to secondary problems such as temporomandibular joint dysfunction. Nocturnal bruxism is noted most prominently during stages 1 and 2 of NREM sleep and REM sleep. These episodes are characterized by stereotypical tooth grinding and is precipitated by anxiety, stress and dental disease. Both diurnal and nocturnal bruxism may be also associated with nocturnal hyperactivity and degenerative disorders such as oromandibular dystonia and Huntington’s disease. It is also commonly noted in children with mental retardation or cerebral palsy. Local injections of botulinum toxin into the Masseter muscle may be used to prevent dental and temporomandibular joint complications.

Sleep terror occurs between the ages of 5 and 7. As with sleepwalking, the subject usually has a family history of sleep terror. Episodes of sleep terror are characterized by intense symptoms, including loud, piercing screams. Patients appear highly confused and fearful. Many patients also have a history of sleepwalking episodes. Precipitating factors are similar to those described in sleepwalking.

In confusional arousal, the patient may have some automatic and inappropriate behavior, including abnormal sexual behavior (sex-somnia or sleep sex) when the episodes occur in adults. The majority of spells are benign, but sometimes violent and homicidal episodes in adults have been described. Precipitating factors are the same as in sleepwalking or sleep terror.

Nightmares are frightening dreams followed by awakening and vivid recall and occur during REM sleep. The most common time of occurrence therefore is from the middle to the late part of the night. Nightmares are typically normal phenomena. Approximately 50% of children have nightmares beginning at age 3-5. The incidence of nightmares continues to decrease as one grows older and the elderly have very few or no nightmares. Nightmares are common after sudden withdrawal of REM-suppressant drugs and can also occur as side effects of certain medications, such as antiparkinsonian drugs, anticholinergics, and beta blockers.

Obstructive Sleep Apnea Syndrome (OSAS)

The symptoms of OSAS can be divided into two groups: those occurring during sleep and those occurring during waking hours. Nocturnal symptoms include habitual loud snoring, choking during sleep, and cessation of breathing and abnormal motor activities during sleep (e.g., shaking and jerking movements, confusional arousals or sleep-walking), severe sleep disruption, heartburn as a result of gastroesophageal reflux, nocturnal bladder incontinence, which is noted mostly in children, and profuse sweating at night. The daytime symptoms include EDS which is characterized by sleep attacks lasting 0.5 to 2 hours, and occurring mostly when the patient is relaxing (e.g., sitting down or watching television). The prolonged duration and the non-refreshing nature of the sleep attacks differentiates them from narcoleptic sleep attacks. In men, impotence is often associated with severe and long-standing cases of OSAS. Physical examination reveals obesity in approximately 70% of cases. Heart failure, mostly systolic, cognitive failure, hypertension and depression are all associated with OSAS. For further details go to the page on obstructive sleep apnea.

Reference: Indian J Med Res 131, February 2010, pp 126-140 and Wikipedia