A disorder, first described in 1965, characterized by recurrent interruptions of breathing during sleep due to temporary obstruction of the airway by lax, excessively bulky, or malformed pharyngeal tissues (soft palate, uvula, and sometimes tonsils), with resultant hypoxemia and chronic lethargy. Sleep in the supine position predisposes apnic episodes. Cf.: central sleep apnea, sleep apnea.
Obstructive sleep apnea (OSA), the most common type of sleep-disordered breathing, affects about 4% of men and 2% of women between the ages of 30 and 60. In addition, it occurs in about 2% of children, largely because of reversible adenotonsillar hyperplasia. It must be distinguished from central sleep apnea, in which apneic episodes during sleep result from impairment of the autonomic respiratory drive. Symptoms are loud snoring, recurrent apneic episodes during sleep followed by gasping inspiration with partial or complete arousal, nocturnal restlessness, and daytime sleepiness. Apneic episodes last 10–120 seconds and may be accompanied by sinus bradycardia or atrioventricular block. The cumulative effect of recurrent spells of apnea is hypoxemia and shallow, nonrefreshing sleep, which may lead to excessive daytime drowsiness, personality change, impairment of intellectual function, and heightened possibility of accidents. However, evidence establishing OSA as an independent risk factor for motor vehicle accidents, heart attack, stroke, and sudden death is weak. Obesity, hypothyroidism, cigarette smoking, alcohol, and some hypnotics (particularly benzodiazepines) predispose to OSA, and its prevalence increases with advancing age. About 35% of people with congestive heart failure and 50% of people with hypertension have this disorder, and 50% of those with this disorder have hypertension. There is also a statistical association between OSA and bilateral leg edema. Diagnosis is confirmed by polysomnography (continuous measurement of airflow, respiratory activity, chin electromyography, ECG, EEG, electrooculogram, and arterial oxygen saturation during sleep) and by evaluation of the shape and size of the upper respiratory tract. Interruption of normal breathing is quantified by the apnea-hypopnea index (AHI), computed by dividing the number of respiratory events (apnea, defined as cessation of air flow for at least 10 seconds, or hypopnea, defined as reduction of air flow by at least 50% for at least 10 seconds) by the total hours of sleep. An AHI of 15 or more indicates significant sleep-disordered breathing. Weight loss, smoking cessation, and avoidance of benzodiazepine hypnotics are advised for all patients. A mandibular advancement appliance worn inside the mouth at night reduces the symptoms in some patients. An effective if somewhat cumbrous treatment is the nightly use of continuous positive airway pressure (CPAP), which provides a steady flow of room air at low pressure through the nose to overcome intermittent upper respiratory obstruction. Selected patients benefit from surgical procedures such as uvulopalatopharyngoplasty (trimming and reshaping of the uvula and soft palate), which can be performed by laser or radiofrequency ablation under local anesthesia, and mandibular osteotomy with genioglossus muscle advancement.
Reference: Stedman's Medical Dictionary