Types of Sleep Disorders

Types of Sleep Disorders

The diagnosis of sleep disorders is key to the appropriate treatment. With the most common sleep disorder, obstructive sleep apnea, the condition usually progresses in a continuum as we age from benign snoring, to upper airway resistance syndrome (UARS), to hypopneas, to obstructive apneas to finally obesity hypoventilation.

UARS stands for upper airway resistance syndrome. It is more often seen in women and younger people. It is defined as a condition in which airway is slightly interfered with making more of an effort to breath, however this slight resistance may not be noticed by the patient or an examining physician. It also might not even be recorded in a standard polysomnogram (PSG) overnight formal sleep study in a sleep clinic. This is because sometimes machines are set to record an event after 10 seconds of either hypopnea or apnea, but if an event is 9 seconds, it may not be recorded. This condition also may not result in decreased blood oxygen levels recorded in a PSG. The diagnosis of this condition might require an additional machine to measure esophageal pressure such as a pharyngometer. Many dental and medical offices do not have this diagnostic device and it is not absolutely required to diagnose and treat sleep disorders.

UARS does not result in airway reduction (hypopnea) nor does it result in apnea (air way stop). It actually just creates more work to breath which may not be noticed by a person suffering from it. It does result in sympathetic stimulation, as apposed to good parasympathetic sleep, which can increase blood pressure and can also result in arousal out of a sleep stage that the body needs for restful sleep. This then produces day time sleepiness (,somnolence) high blood pressure and many other ailments. Interestingly, this condition can also result in abnormal low blood pressure (hypotension) and some patients are misdiagnosed with fibromyalgia and similar disorders. This disorder is a smaller part of the overall sleep disorders spectrum. Snoring is common in this disorder.


Hypopnea is defined as reduced air flow but not absence of air flow. It does result in lower blood oxygen levels. This condition is essentially just as damaging to health as is apnea, or the complete stopping of air flow for short periods of time. Hypopneas and apneas are most often grouped together in the number of events per hour and is called the (AH I) or the apnea hypopnea index.

Hypopneas can be caused by low air flow or slowed respiratory rate. It is usually recorded when there is a 30% or greater reduction in air flow and 4% reduced oxygen saturation in the blood and this occurs for at least 10 seconds. If these reductions in oxygen or air flow rate are caused by a central interference or failure of the brain to signal a breath, then an oral appliance would not be the treatment of choice. The vast majority of hypopneas and apneas are not cause by central or signal issues. In some cases the problem can be a mixture of central and obstructive and depending on the ratio of the two oral appliances may still be of benefit or can be used in combination with CPAP/BPAP.

Apnea (OSA)

Sleep apnea is defined as a suspension of breathing, It is either caused by blockage or it is caused by the brain not signaling the lungs muscles to breath. There are causes such as certain drugs and other pathological conditions too.

By definition, there must be an average of 5 or more events per hour to have an abnormal condition. Some severe conditions can have more than 50 per hour. In apnea blood oxygen is reduced in concentration and carbon dioxide builds up in the blood, receptors stimulating the brain to wake you up so that you will breath again. This is very disruptive to sleep patterns and also releases a lot of stress hormones such as cortisol into the blood stream. Excessive daytime sleepiness (EDS) may be present but not always. The sympathetic nervous system is stimulated too.

This cessation of breathing or blockage of breathing can last from several seconds to over a minute and sometimes longer. Once a person awakes and gasps for air, oxygen is restored and they go back to sleep, only to repeat the cycle. Sleep studies typically record this event only if it is 10 seconds or longer.

Sleep apnea is classified as dyssomnia and is very dangerous to your health. Most people are unaware of it on their own but only become aware if others report seeing them or hearing them experience it.

Apnea can occur in obesity hypoventilation syndrome ( OHS) in which a person is affected in such a way that even daytime high carbon dioxide levels in the blood (hypercapnea) are higher than normal. Right side heart muscle is stressed creating heart failure and swollen legs. Weight loss is needed to treat this condition along with CPAP/BPAP and can include oral appliances and orthodontic care with TMJ treatment.

Apnea Hypopnea Index (AHI)

The apnea hypopnea index is a common measure that combines the number of apnea events and hypopnea events in an hour. The ranges include: Less than 5 events AHI = <5 is considered normal and usually not treated. An AHI of 5 to to 15 is considered mild sleep apnea. An AHI of 15 to 30 is considered moderate sleep apnea and any reading over 30 is considered severe sleep apnea.

Other Definitions and Causes

There are other causes of sleep disorders that are not within the scope of information appropriate for this web site to the general population. Diagnostic terms that may show up on your sleep study report such as RDI, RERAS and ODI, among others, may be explained to your by your treatment professional and you are encouraged to have these discussions with him or her.

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