• How do physicians determine the severity of a person's sleep apnea?
• How is the mildest case of sleep apnea distinguished from normality?

Judging the Severity of a Sleep Apnea Case

Sleep apnea severity is judged in two major ways:

• According to the amount by which airflow is disturbed, or
• According to the consequences of the disturbed airflow.

In principle, a physician could rate the severity of a person's sleep apnea using any of the criteria in the chart below.

Criterion			Range of Severity
Airflow
	Number of airflow drops:		5/hour		120 per hour (or more)
Consequences
	Symptoms:		None		Incapacitating
	Heart function:		Normal		Severely disturbed
	Blood pressure:		Normal		Very high
	Blood oxygen:		Normal		Large, frequent drops

Experts are not sure of the best method. Today, the number of airflow drops and the degree of symptoms are the criteria most often used to judge severity. These criteria may be used to decide when and how to treat sleep apnea.

With more research on the long-term effects of sleep apnea, it is possible that heart function and blood pressure may become more frequent considerations in treatment decisions.

The American Academy of Sleep Medicine has published methods for grading the severity of sleep apnea.  The first method is based on the number of significant drops in airflow per hour of sleep:

Severity		Airflow drops per hour of sleep
Mild		5 to 15
Moderate		15 to 30
Severe		30 or more

The second method is based on symptoms of sleep apnea:

Severity	Symptoms
Mild	Unwanted sleepiness or involuntary sleep episodes occur during activities that require little attention. Examples include sleepiness that is likely to occur while watching television, reading, or traveling as a passenger. Symptoms produce only minor impairment of social or occupational function.
Moderate	Unwanted sleepiness or involuntary sleep episodes occur during activities that require some attention. Examples include uncontrollable sleepiness that is likely to occur while attending activities such as concerts, meetings, or presentations. Symptoms produce moderate impairment of social or occupational function.
Severe	Unwanted sleepiness or involuntary sleep episodes occur during activities that require more active attention. Examples include uncontrollable sleepiness while eating, during conversation, walking, or driving. Symptoms produce marked impairment in social or occu-pational function.

The current definition of sleep apnea is 5 or more airflow drops per hour of sleep.

Because so many people meet this criterion (1 in 5 American adults), some experts believe 5 drops per hour is too low, and that 10 or 15 is better. Other experts believe that the diagnosis of sleep apnea should not be made unless the patient has sleepiness as a symptom.

On the other hand, another group of experts believe that sleep apnea should be diagnosed in some persons having fewer than 5 airflow drops per hour of sleep.

• Some experts think children having 1 or more airflow drops per hour should be diagnosed as having sleep apnea.
• Some studies have shown that adults having less than 5 airflow drops per hour of sleep raises the risk of developing high blood pressure.
• There is a condition called UARS (upper airway resistance syndrome) that is very similar to sleep apnea. A person with UARS can have all the consequences seen in persons with sleep apnea, but can have zero airflow drops per hour of sleep.

The current state of knowledge about sleep apnea is similar to the state of knowledge about high blood pressure decades ago. In the 1950s, experts knew that high blood pressure was bad, but they did not have enough research evidence to determine the blood pressure where normal turns into "bad." As more and more knowledge about blood pressure has accumulated, the "bad" level has been getting lower and lower.

Finally, there is debate about the definition of an "airflow drop." There are many possible ways to determine whether a drop in airflow has occurred. The degree of airflow drop that qualifies as "significant" is also debatable.

In summary, it will take a great deal of research work to definitively determine the point at which sleep breathing becomes abnormal. It is very likely that the point will be different for people who have heart disease, compared to persons who do not.