Sleep-wake disorders encompass insomnia, hypersomnolence, narcolepsy, breathing-related sleep disorders, circadian rhythm sleep-wake disorders, nonrapid eye movement (NREM) sleep arousal disorders, nightmare disorder, rapid eye movement (REM) sleep behaviour disorder, restless legs syndrome, and substance/medication-induced sleep disorder.
WHAT ARE THE CAUSES OF SLEEP-WAKE DISORDERS?
Humans typically have four to six cycles of NREM and REM sleep each night, each cycle lasting 70 to 120 minutes. Usually, there is a progression through the four stages of NREM sleep before the first REM period.
Stage 1 of NREM is the stage between wakefulness and sleep. Stages 3 and 4 sleep are called delta sleep (i.e., slow-wave sleep).
In REM sleep, there is a low-amplitude, mixed-frequency electroencephalogram, increased electrical and metabolic activity, increased cerebral blood flow, muscle atonia, poikilothermia, vivid dreaming, and fluctuations in respiratory and cardiac rate.
The elderly have lighter, more fragmented sleep with more arousals and a gradual reduction in slow-wave sleep.
REM sleep is turned on by cholinergic cells. Dopamine has an alerting effect. Neurochemicals involved in wakefulness include norepinephrine and acetylcholine in the cortex and histamine and neuropeptides (e.g., substance P and corticotropin-releasing factor) in the hypothalamus.
Polysomnography (PSG) measures multiple electrophysiologic parameters simultaneously during sleep (e.g., electroencephalogram, electrooculogram of each eye, electrocardiogram, electromyogram, air thermistors, abdominal and thoracic strain belts, and oxygen saturation) to characterise sleep and diagnose sleep disorders.
WHAT ARE THE SIGNS AND SYMPTOMS OF SLEEP-WAKE DISORDERS?
Patients with insomnia complain of difficulty falling asleep, maintaining sleep, or experiencing nonrestorative sleep.
Transient (two or three nights) and short-term (less than 3 months) insomnia is common. Chronic insomnia (more than 3 months duration) occurs in 9% to 12% of adults and in up to 20% of the elderly.
Causes of insomnia include stress; jet lag or shift work; pain or other medical problems; mood or anxiety disorders; substance withdrawal; stimulants, steroids, or other medications.
In patients with chronic disturbances, a diagnostic evaluation includes physical and mental status examinations, routine laboratory tests, and medication and substance abuse histories.
Genomic Medicine UK is the home of comprehensive genomic testing in London. Our consultant medical doctors work tirelessly to provide the highest standards of medical laboratory testing for personalised medical treatments, genomic risk assessments for common diseases and genomic risk assessment for cancers at an affordable cost for everybody. We use state-of-the-art modern technologies of next-generation sequencing and DNA chip microarray to provide all of our patients and partner doctors with a reliable, evidence-based, thorough and valuable medical service.