Upper airway resistance syndrome is a sleep disorder characterized by the narrowing of the airway that can cause disruptions to sleep. The symptoms include unrefreshing sleep, fatigue, sleepiness, chronic insomnia, and difficulty concentrating. UARS can be diagnosed by polysomnograms capable of detecting Respiratory Effort-related Arousals. It can be treated with lifestyle changes, orthodontics, surgery, or CPAP therapy. UARS is considered a variant of sleep apnea, although some scientists and doctors believe it to be a distinct disorder. History
Upper airway resistance syndrome was first recognized at Stanford University in the late 1980s and the article that described it by name along with its relationship to OSA was published in 1992 by Dr. Christian Guilleminault et al. Signs and symptoms
Symptoms of UARS are similar to those of obstructive sleep apnea, but not inherently overlapping. Fatigue, insomnia, daytime sleepiness, unrefreshing sleep, anxiety, and frequent awakenings during sleep are the most common symptoms. Oxygen desaturation is minimal or absent in UARS, with most having a minimum oxygen saturation >92%.Many patients experience chronic insomnia that creates both a difficulty falling asleep and staying asleep. As a result, patients typically experience frequent sleep disruptions. Most patients with UARS snore, but not all.Some patients experience hypotension, which may cause lightheadedness, and patients with UARS are also more likely to experience headaches and irritable bowel syndrome.Predisposing factors include a high and narrow hard palate, an abnormally small intermolar distance, an abnormal overjet greater than or equal to 3 millimeters, and a thin soft palatal mucosa with a short uvula.
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.