In patients with obstructive sleep apnea (OSA), this results in partial or complete airflow obstruction.These events are accompanied by increasing respiratory efforts and oxygen desaturation, which trigger arousals in order to increase airway tone and restore normal breathing. OSA is defined by repetitive upper airway obstruction during sleep, with resultant cessation of airflow despite on-going respiratory efforts. OSAS is the manifestation of adverse effects on health and cognition in patients with OSA.

Epidemiology
OSAS is reported to occur in at least 2% of adult women and 4% of adult men in the US. Many estimate the true burden of OSAS to be significantly higher. In fact, its prevalence is rapidly increasing, likely resulting from increasing disease awareness, aging of the population and the obesity epidemic.

Numerous individual variables have been associated with an increased frequency of OSAS, including advanced age, male gender, and craniofacial abnormalities such as micrognathia, retrognathia, or increased Mallampati scores. Obesity and markers of obesity such as an elevated body mass index (BMI) or increased neck circumference are also more common. Other predictors of OSAS include habitual snoring, witness apneas, restless sleep, hypothyroidism, and cardiovascular disease. However, many patients with OSAS do not exhibit the classic patient profile and this disorder is becoming increasingly recognized in young, physically fit, non-snoring individuals.

Evalaution and Diagnosis
The diagnosis of OSA requires documentation of obstructive respiratory events during overnight polysomnography. The frequency of these events per hour of sleep determines the respiratory disturbance index (RDI). Disease severity is defined by the RDI, with greater than 5, 15 and 30 representing mild, moderate, and severe disease, respectively.While OSA is determined by polysomnography, OSAS requires the presence of OSA associated with excessive sleepiness and/or any of the associated complications presented below.

Clinical Manifestations

Neuropsychological Impairment
Neurocognitive sequelae have been well documented in patients with OSAS. Repetitive arousals cause frequent sleep stage shifts and abnormal sleep architecture, with truncation of both slow-wave and rapid eye movement sleep. This diminishes restorative sleep and sleep continuity, which may promote depression, cognitive impairment, and excessive daytime sleepiness. As a result, work-related and motor vehicle accidents are substantially more common in patients with OSAS.