Associated With Mental Disorders. Disordered sleep is typical of most psychiatric disorders. Unipolar depression is characteristically associated with a disorder of initiating and maintaining sleep, most commonly early morning awakening. The patient may fall asleep easily but wake a few hours later, alert and unable to return to sleep. This can be the earliest symptom apparent to the patient. Sleep studies in some of these patients demonstrate an earlier-than-normal REM latency and increased phasic REM activity early in the night. In contrast, the sleep in bipolar depressive disease is characterized by prolonged periods of inability to sleep during the manic phase and excessive sleep during the depressive phase. Most actively psychotic patients have difficulty maintaining sleep, but some may be hypersomnolent at the onset of their psychosis. Patients with panic disorder may wake suddenly at night with panic; polysomnographic evaluation is sometimes useful to distinguish these episodes from sleep terror or seizure. The treatment of sleep disorders of psychiatric cause is directed to treatment of the underlying illness. Improvement in sleep is often a sensitive measure of the effectiveness of treatment.

Associated With Neurologic Disorders
Cerebral degenerative disorders, dementia, parkinsonism. Sleep disruption is a prominent, but not well studied, symptom in all of the degenerative diseases of the brain. Patients with degenerative disease of the brain are at particular risk for sleep-disordered breathing produced by Cheyne-Stokes respirations, abnormal chest wall and upper airway muscle tone, brain stem dysfunction, and use of sedating medications. The resulting hypoxemia can contribute to episodes of nocturnal confusion. In the disorders involving motor systems, sleep fragmentation also occurs secondary to rigidity, tremor, myoclonus, and periodic limb movements. Brain stem involvement induces REM sleep abnormalities, including REM sleep behavior disorder. REM behavior disorder may be the presenting symptom of Parkinson’s disease and Shy-Drager syndrome (multisystem atrophy) years before other abnormalities are detected. Circadian rhythm disorders in the degenerative diseases are frequent and probably represent derangement of neurologic control mechanisms, coupled with the secondary effects of disrupted sleep and medication.

Sleep-related epileptic seizures are facilitated by sleep, particularly stage II sleep. Hypoxia secondary to sleep apnea also precipitates seizures. Some types of seizure disorders, especially complex partial seizures with temporolimbic symptoms, closely mimic sleep terrors and sleepwalking. Usually the clinician is alerted by features that would be atypical of delta sleep arousals, including recurrent episodes during the same night, history of seizures, or abnormal neurologic examination. Nocturnal wandering secondary to epilepsy tends to be less well organized and goal directed. Grand mal seizures are suggested by falls from bed, incontinence, bitten tongue, and morning confusion.

Sleep-related headaches are of various types. Cluster headache is a severe unilateral orbital headache associated with ipsilateral rhinorrhea and tearing. The headache is frequently nocturnal and appears to be exacerbated specifically by REM sleep. Chronic paroxysmal hemicrania, a similar headache disorder that occurs more frequently in women and is responsive to indomethicin, is also REM related. Increased blood flow and hypoxemia during REM may be etiologic factors. Most patients note that migraine is improved by sleep, but occasionally the reverse is true. Sleep-related headache may be the presentation of increased intracranial pressure, which is exacerbated by the supine posture and episodic elevation in intracranial pressure during REM sleep. Morning headache is typical of sleep apnea syndrome and bruxism.

Associated With Other Medical Disorders. Just as medical illness disrupts the quality of life during the day, it also affects the maintenance of sleep. A careful consideration of possible systemic disease is important in every patient with a sleep disorder. Almost every disease, at some point in its course, may disrupt sleep. Most painful disorders cause nocturnal arousal, especially arthritis and peptic ulcer disease. Insomnia may be the presenting complaint of congestive heart failure with nocturia, paroxysmal nocturnal dyspnea, or arousal secondary to Cheyne-Stokes respirations. Pulmonary dysfunction is exacerbated during sleep and predisposes patients to sleep-disordered breathing. Sleep disruption is particularly prominent in hyperthyroidism and uremia.