upper airway resistance syndrome

Upper airway resistance syndrome is the subtle end of the sleep-disordered breathing spectrum: the throat narrows enough to make breathing hard work and to repeatedly disturb sleep, but never enough to cause full apneas or marked drops in oxygen. The sleeper labors against a partly closed airway all night, waking the brain again and again, while a simple oximeter may show almost nothing wrong.

Physiologically, the narrowed pharynx raises the resistance to airflow, so the body must generate greater and greater breathing effort — more negative pressure with each inhalation — to keep air moving. When that effort crosses a threshold, it triggers a respiratory effort–related arousal. These arousals accumulate, fragmenting sleep, even though airflow and oxygen stay within the limits used to score apneas and hypopneas.

Clinically it can look like sleep apnea without the apnea: people report unrefreshing sleep, daytime sleepiness or fatigue, difficulty concentrating, and sometimes headaches; many also have features such as low blood pressure, lightheadedness, or functional complaints. Snoring may be present or absent. The disorder is more commonly recognized in younger and slimmer patients, including women, who do not fit the classic apnea picture.

Because the apnea–hypopnea index and oxygen desaturation index can be normal, diagnosis hinges on detecting the increased breathing effort and the arousals it causes, which requires sensitive monitoring such as full polysomnography rather than basic home oximetry. Treatment overlaps with obstructive sleep apnea — CPAP, oral appliances, and addressing nasal or anatomical narrowing. A frank caveat: UARS remains debated, with some experts viewing it as part of a continuum rather than a wholly separate entity.