Sleep Disorders

Diagnosis of sleep disorders

Biological markers for sleepiness are not viable the way they are for many illnesses. Although blood chemistry changes a little when a person is sleepy, the change is very small, serum levels of hormones and components differ widely, and the systems that make a person sleepy are complicated.

Polysomnography is not widely used in the diagnosis of insomnia. It is generally expensive and the accepted clinical definition of insomnia incorporates the patient's subjective assessment in a way that PSG cannot capture. Indeed, many people clearly suffer from chronic insomnia show decent results in a PSG (under 30 min sleep latency, over 85% sleep efficiency).

Further, many insomniacs think they are awake even when the PSG results show they are asleep. This has been documented by studies. The International Classification of Sleep Disorders criteria calls this a “sleep-state misrepresentation”. The American Psychiatric Association's Diagnostic and Statistical Manual of Mental DIsorders (DSM-IV) has no classification for this.

A thorough examination and accurate diagnosis of insomnia requires the patient's medical, psychiatric, and sleep history. It's hard for the doctor to distinguish between primary and secondary insomnia, and what other maladies may be present. Insomnia, the most common sleep disorder, even has subtle differences in official definitions.

The International Classification of Diseases most recent guidelines (ICD-1) defines insomnia as

Difficulty falling asleep
Difficulty maintaining sleep, or
Non-refreshing sleep

happening three or more times a week for longer than a month, and causing distress to the patient or intefering with the patient's daily life.

The American Psychiatric Association's DSM-IV (Diagnostic and Statistical Manual of Mental Disorders) likewise lists the critera for insomnia as complaints about

Difficulty initiating sleep
Difficulty maintaining sleep, or
non-restorative sleep

for a period of a month and where the patient has distress or the insomnia interferes with his or her life.

The International Classification of Sleep Disorders (written by sleep professionals) includes waking up too early as a sign of insomnia and has no specific time before it can be diagnosed so long as some daytime impairment happens.

Standard questionairres and scoring systems can help. Many sleep experts employ the Pittsburgh Sleep Quality Index.

Actigraphic assessment is also useful although like PSG the results often disagree with subjective assessment. To get an actigraphic reading, the patient wears a device on the wrist or ankle to measure motor activity during the night for a couple of weeks. Actigraphs are effective at distinguishing between primary insomnia and a circadian rhythm disorder. New home use devices that let users see their sleep architecture have been introduced, although they are not considered definitive for diagnosis of sleep disorders

Sleep logs or diaries are also valuable to the diagnosing doctor. These diaries record bedtime, estimated time to fall asleep, number of awakenings, wake-up time, use of medicines, and subjective quality of sleep. These diaries are typically filled out in the mornings, and over a period of several months they can paint a picture of the patient's situation for the diagnosing physician. More on sleep histories.

Patient interviews: Professional groups also recommend that doctors directly ask patients how they have been sleeping during a routine checkup. Surveys show most people who believe they have chronic insomnia have never discussed the problem with a doctor.

Diagnostic scales

Sleepiness is a subjective feeling, but it is worth trying to quantify at times. Society doesn’t want sleep ypeople working in critical jobs and the diagnosis of many dyssomnias is aided by knowing how sleepy people are.

The methods of quantifying sleepiness generally rely on reports from the subject and observations of behavior rather than an fMRI or blood test or some other methods of looking inside the body.

Epworth Sleepiness Scale

Pittsburgh Sleep Quality Index

Stanford Sleepiness Scale

Fatigue Severity Scale

Insomnia Impact Scale

Maintenance of Wakefullness Test

Multiple Sleep Latency Test

The OSLER (Oxford SLEep Resistance test) is used by some researchers, as it is easier to administer than the MWT test. The detection of sleepiness is done by observing the patient’s behavior (response to a task of pressing a button after light flashes) rather than an EEG that the MWT test uses.

Pupillometry – measuring who wide the pupils are – is one method. Pupils expand and contract in response to light, and an alert, well rested person will have pupils that maintain their size during darkness. Sleepy people, on the other hand, will have pupillary oscillations in darkness. Preliminary work on this method for quantifying sleepiness has used a time period of 15 minutes for these tests and has been able to correlate the results to results from other sleepiness tests. However, pupillometry is not widely used, at least yet.