Laboratory and Imaging Studies
Laboratory studies appropriate for those with sleep disorders include the following:
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Hemoglobin and hematocrit
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Arterial blood gases
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Thyroid function tests
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Drug and alcohol toxicology screening
Oximetry may be performed during sleep to examine blood oxygen levels for clinically important desaturations suggestive of sleep apnea or other forms of sleep-disordered breathing.
Although no imaging studies are directly indicated for the workup of insomnia, underlying medical conditions call for appropriate investigation using suitable studies.
Indices and Scoring Systems
A Beck Depression Index or similar clinical screening tool may be used to detect an underlying depressive illness as a contributing factor in insomnia.
An Epworth Sleepiness Score or another objective measure of daytime sleepiness may lead to clues to the presence of another underlying sleep disorder. For example, approximately 20% of patients with sleep apnea present with a history of nighttime insomnia; however, patients are excessively sleepy by day and have an abnormal score on the Epworth Sleepiness Scale.
Sleep Journal
Subjective measures of sleep are obtained by means of a sleep journal. A sleep journal kept for approximately 2 weeks may help determine the extent of the sleep disturbance. Patients should record the total hours slept per night, the frequency of nighttime awakenings, and the level of restfulness provided after sleep.
Additional, more objective measures of sleep may be available if a patient has a sleep partner who keeps a 2-week journal or provides a relevant history.
Electroencephalography and Polysomnography
Objective measures of sleep may be obtained by means of electroencephalography (EEG) or polysomnography (PSG). These studies may be helpful in determining sleep and wakefulness in the intensive care unit (ICU) or in the sleep laboratory.
Monitored PSG is the standard for evaluating measures of sleep. This study includes measures of multiple channels of EEG, electrooculography (EOG), chin and leg electromyography (EMG), nasal and oral airflow, oximetry, abdominal and chest movements, and electrocardiography (ECG). Monitored PSG can help the physician discriminate between rapid eye movement (REM) sleep and non-REM (NREM) sleep, as well as determining causes of sleep disturbance.
Patients with chronic medical conditions, such as fibromyalgia or anxiety disorders, often have characteristic alpha brain-wave activity that intrudes into the deeper stages of sleep. This activity can readily be seen on the EEG during PSG. Patients with insomnia often have some degree of sleep-state misperception, wherein they perceive and believe that they achieve significantly less sleep than they actually do. This can be documented by correlating the EEG findings from the PSG with patient subjective reports of sleep duration and onset.
