In 88% of the subjects, there is a history of early extraction or absence of wisdom teeth. There is an increased prevalence of UARS in east Asians. Pathophysiology
Upper airway resistance syndrome is caused when the upper airway narrows without closing. Consequently, airflow is either reduced or compensated for through an increase in inspiratory efforts. This increased activity in inspiratory muscles leads to the arousals during sleep which patients may or may not be aware of.A typical UARS patient is not obese and possesses small jaws, which can result in a smaller amount of space in the nasal airway and behind the base of the tongue. Patients may have other anatomical abnormalities that can cause UARS such as deviated septum, inferior turbinate hypertrophy, a narrow hard palate that reduces nasal volume, enlarged tonsils, or nasal valve collapse. UARS affects equal numbers of males and females.Why some patients with airway obstruction present with UARS and not OSA is thought to be caused by alterations in nerves located in the palatal mucosa. UARS patients have largely intact and responsive nerves, while OSA patients show clear impairment and nerve damage. Functioning nerves in the palatal mucosa allow UARS patients to more effectively detect and respond to flow limitations before apneas and hypopneas can occur. Patients with intact nerves are able to dilate the genioglossus muscle, a key compensatory mechanism utilized in the presence of airway obstruction.
This method increases the volume of the nasal cavity and nasopharynx, leading to increased airflow and reduced respiratory arousals during sleep. See also

Airway resistance
Sleep apnea


== References ==