Sleep Disorders

Diagnosis of sleep disorders

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.

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.

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.

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.