• Statistics on under-diagnosis
• Reasons for under-diagnosis
• Current methods of diagnosis
• References

It is difficult to find reliable data on the rate of sleep apnea diagnosis in the United States. Data from a Wisconsin study in the 1990s is used in the chart below.

The chart shows the number of adults in the United States with sleep apnea.  It also shows the number with symptoms of sleep apnea and the number who have been diagnosed as having sleep apnea. There are about 200 million adults in the United States.

	40 million have sleep apnea
	10 million have sleep apnea + symptoms
	.6 million have sleep apnea + symptoms + are diagnosed

Sleep apnea has become more widely diagnosed since the 1990s,  but the message of the statistics is unmistakable and remains unchanged: sleep apnea is massively under-diagnosed. We conservatively estimate that 90 to 95% of persons with sleep apnea have not been diagnosed.

Only the tip of the sleep apnea iceberg has been seen.

Sleep apnea is under-diagnosed for several reasons:

• The symptoms of sleep apnea are often vague.
• Symptoms develop slowly, so patients may not realize they have become sick.
• The patient is not able to sense or remember the active state of the disease during sleep.
• Knowledge of the disease by physicians is low.
• The test normally used to diagnose sleep apnea is expensive and specialized.

Talking to the patient and examining the patient are the first steps in all medical diagnosis. Except in very severe cases, the history and physical examination of patients with sleep apnea are not very accurate. Even physicians who specialize in sleep disorders have difficulty making the diagnosis without doing tests.

The definitive way to determine whether a person has sleep apnea (or not) is to have the person undergo a test called polysomnography (PSG). Other types of tests have been proposed, but none have had accuracy and experience sufficient to gain acceptance.

A PSG is normally conducted in a special-purpose facility called a sleep laboratory. A typical sleep lab has several rooms outfitted something like hotel rooms. (The degree of luxury or simplicity is variable.) The person undergoing the PSG sleeps in the room, while 15 or more wires are attached to his or her skin. The wires record electrical and other signals from the person's body. These signals are collected all through the night, and are later analyzed to determine whether the person had sleep apnea during the night, and if so, to what degree.

PSG tests are expensive and difficult to perform well. There are not enough sleep laboratories available to test everyone who might have sleep apnea. There are not enough sleep laboratories to test a person on a recurring basis over months or years.

Although many people blame the expense, difficulty, and scarcity of PSG testing as the main reason that sleep apnea is under-diagnosed, we take a different view. We believe the major problem in diagnosis has been the lack of tools to help physicians utilize the PSG efficiently.