Sleep Apnea Syndrome (SAS)
SAS is a breathing disorder. Numerous studies report a 4% incidence of SAS in adult males and 2% in adult females. SAS is characterized by apneas and hypopneas.
Apnea is characterized by a complete cessation of airflow at the nostrils and mouth lasting at least 10 seconds in adults.
Hypopnea is an episode of reduction reduced airflow but not a complete cessation lasting 10 seconds or longer in adults.
Both apneas and hypopneas are associated with a sleep arousal and/or oxygen desaturations of 3% or more. Apneas and hypopneas result from upper airway occlusion, either full or partial, or from a loss of the autonomic drive to breathe. There are four types of apnea: obstructive, central, mixed and complex.
Obstructive Sleep Apnea (OSA)
OSA is characterized by a complete cessation of airflow with continued efforts to breathe lasting 10 seconds or longer in adults.. OSA’s are usually associated with a reduction in blood oxygen saturation. The primary causes are lack of muscle tone during sleep, excess tissue in the upper airway, and anatomic abnormalities in the upper airway and jaw. OSA is the most common type of sleep apnea.
Central Sleep Apnea (CSA)
CSA is characterized by a cessation or decrease of ventilatory effort during sleep. The term "central" is used to classify the events as being due to decreased output from the central nervous system to the muscles. CSA affects only 5-10% of the sleep apnea population.
Mixed apneas refer to respiratory events during sleep that have features of both obstructive apnea and central apnea in the same event.
Complex Sleep Apnea
This has been recently described by researchers as a novel presentation of sleep apnea. Patients with complex sleep apnea exhibit OSA, but upon application of positive airway pressure the patient exhibits persisten central sleep apnea. Adaptive servo-ventilation has been introduced to treat these patients.
Primary Symptoms of SAS:
- EDS (excessive daytime somnolence)
- Witnessed apneas
- Snoring (generally associated with OSA, not CSA)
- Irregular breathing during sleep
- Impaired memory
- Impaired concentration
- Feeling of clumsiness
- Morning headaches
- Mood changes, such as irritability and sadness
- Sexual dysfunction
Researchers continue to develop an understanding of the risks created by and associated with SAS. Associated risks include the following:
- CHF (Congestive Heart Failure)
- Traffic Accidents (from sudden onset of sleep)
Three recent studies examined the link between SAS and hypertension:
- Lavie et al. (2000) demonstrated that SAS has a profound association with hypertension independent of all other risk factors.
- Nieto et al. (2000) demonstrated that sleep disturbed breathing is associated with systemic hypertension in middle aged and older individuals of both sexes (after controlling for potential confounding factors).
- Peppard et al. demonstrated that sleep disordered breathing is a risk factor for hypertension and cardiovascular morbidity in the general population (independent of known confounding factors). Peppard's study actually establishes untreated SAS as a cause for hypertension.
Researchers have known for some time that sleepy drivers cause a large number of traffic accidents. Researchers have also known that individuals with SAS have an increased risk of involvement in traffic accidents. Two recent studies look specifically at the probability of traffic accidents for people with SAS:
Teran-Santos et al. (1999) found that individuals with SAS are over six times more likely to be involved in a traffic accident than individuals that did not have SAS.
Horstmann et al. (2000) found that individuals with SAS are 15 times more likely to be involved in a traffic accident than individuals that did not have SAS.
Diagnostic Testing of SAS
There are a number of methods to diagnose SAS. Until recently, patients had to undergo full polysomnography (PSG), which measures a large number of parameters, including electroencephalography (EEG), electro-oculography (EOG), and electromyography (EMG) as well as respiratory information, such as airflow, respiratory effort, snoring and oxygen saturation monitoring. Leg movements are also commonly measured to determine the presence of PLMS. Clinicians now have a variety of diagnostic procedures to choose from:
- Full PSG
- Limited channel sleep study
- Portable Sleep Testing
- CPC Technology (Do we want to add something about this here?)
Regardless of which diagnostic test is used, a clinical history of sleep apnea and a consultation with a sleep specialist are integral to the diagnosis.