To be classified as "obstructive" sleep apnea, the condition includes at least five obstructed breathing events (apnea or hypoapnea) per hour of sleep and the coexistence of unexplained excessive daytime sleepiness. The frequency of obstructed breathing events in the elderly may be higher. Snoring usually accompanies sleep apnea.

Central sleep apnea involves respiratory pauses caused by lack of respiratory effort. It is most commonly found in the presence of cardiac failure or neurologic disease, especially stroke. It is less common than obstructive sleep apnea. Mixed apnea is a combination of the absence of respiratory effort (central sleep apnea) combined with upper airway obstruction (obstructive sleep apnea).

This condition occurs most often in fairly to severely overweight persons who usually attempt to sleep lying on their backs with their faces upward. The airway is sucked closed on inspiration during sleep as the muscles of respiration relax upon falling sleep. Individuals with obstructive sleep apnea have narrow airways that can be associated with obesity but also with shortening of the mandible or maxilla (jaw structure). Hypothyroidism and acromegaly predispose individuals to obstructive sleep apnea as do male gender, myotonic dystrophy, Ehlers-Danlos syndrome and perhaps smoking.

Manifestations range from mild to severe. Obstructions that occur during sleep on a continual basis may cause a cycle that consists of: sleep, obstructive choking, and arousal with gasping for breath.

Daytime drowsiness, impaired vigilance, cognitive performance and difficulty driving; depression; disturbed sleep; and hypertension may occur. There may be an increase in the risk of myocardial infarction (heart attack) and stroke in individuals with obstructive sleep apnea. Other symptoms include difficulty concentrating, unrefreshing nighttime sleep, nighttime choking, nocturia and decreased libido.

Polysomnography is done to confirm the diagnosis of obstructive sleep apnea and to evaluate the severity. Thyroid function tests can help diagnose hypothyroidism (underactive thyroid function) and genetic testing can confirm acromegaly and Ehlers-Danlos syndrome.

A variety of treatments may have to be attempted to improve the condition since it is chronic and is known to relapse. For example, for obesity-related sleep apnea, weight reduction lessens the number of episodes and nasal continuous positive airway pressure (CPAP) can be used to assist during weight loss.

For obstructive sleep apnea, nasal CPAP is usually used right away. In patients who are very ill, nasal CPAP is used during polysomnography, and oxygen may also need to be given. The benefit of the nasal CPAP is usually evident in 1 to 2 nights. In addition, dental appliances may be fitted to assist patients with obstructive apnea. Patients who snore, are advised to avoid alcoholic beverages, tranquilizers, sleeping pills, and antihistamines before sleep; sleep in a prone position on to the side; and to raise the head of the bed. Surgery is rarely considered. However, for heavy snoring, surgical correction of the obstruction in the nose, pharynx or uvula may be the only solution. Finally, if patients have severe heart or pulmonary disease, tracheostomy may be indicated.

Continuous positive airway pressure (CPAP) improves breathing during sleep, sleep quality, sleepiness, blood pressure, vigilance, cognition and driving ability in individuals with obstructive sleep apnea. Excessive daytime sleepiness in individuals with obstructive sleep apnea that is not relieved with continuous airway positive pressure (CPAP) may respond to the drug, modafinil. Central sleep apnea may be successfully treated with the drug, acetazolamide.

Bariatric surgery can be curative for the morbidly obese. Jaw advancement surgery is effective in those individuals with retrognathia (posterior displacement of the mandible) and should be considered in young and thin individuals. Uvulopalatopharyngoplasty (uvula, palate, or pharynx surgery) does not show evidence of curing obstructive sleep apnea. After surgery, individuals must still continue to use CPAP for the rest of their lifetime. Surgical correction of nasal obstruction helps relieve apnea in some individuals. CPAP is effective in only a minority of individuals with central sleep apnea.

CPAP has been shown to be the most effective therapy for obstructive sleep apnea. Although CPAP is an obtrusive therapy, its success depends on explaining the need for treatment to the individual and his/her partner, and to support patients on CPAP intensively by providing regular follow-up evaluations. The main side effect of CPAP therapy is airway drying which can be countered using an integral heated humidifier. Other difficulties with CPAP include the need for adjusting airway pressure periodically and finding a facial mask that is properly fitted and comfortable for the user. After 5 years of objective monitoring, 94% of supported individuals continue with CPAP therapy. Individuals with sleep apnea who have strokes or myocardial infarctions (heart attacks) are more likely to die from these complications than those individuals who do not have sleep apnea.

• May be entitled to special monthly compensation where the Veteran has a single service-connected disability rated as 100% with additional service-connected disability or disabilities independently ratable at 60% or more, which are separate and distinct from the 100% service-connected disability and involves different anatomical segments or bodily systems. See  38 CFR 3.350(i)(1) – Special Monthly Compensation (SMC).

• Review special provisions regarding the evaluation of specific respiratory conditions under 38 CFR 4.96(a) - Rating co-existing respiratory conditions.