Upper Airway Resistance Syndrome (UARS): When Your Sleep Study Looks Normal But You're Still Exhausted

By Dr. Boris Zusin · Published September 8, 2026

Some patients describe every classic symptom of sleep apnea — daytime exhaustion, restless sleep, frequent awakenings — and then go for a sleep study that comes back essentially normal: no apneas, no hypopneas, no oxygen desaturation. That combination doesn't necessarily mean the symptoms are unrelated to breathing during sleep. It can point toward a separate, related condition called upper airway resistance syndrome (UARS), first described in the early 1990s and still commonly under-recognized today.

What UARS Actually Is

UARS describes a pattern where the airway narrows during sleep — increasing resistance to airflow and the effort it takes to breathe — without narrowing enough to produce the full apneas, hypopneas, or oxygen drops that define obstructive sleep apnea (OSA) on a standard sleep study. Instead of showing up as a countable respiratory event, the increased breathing effort itself triggers brief, repetitive arousals that fragment sleep just as effectively as full apneas do, without necessarily being flagged by conventional scoring. The distinction matters clinically: a standard diagnostic sleep study measures airflow and oxygen levels, but detecting the subtler increased respiratory effort that defines UARS traditionally required specialized monitoring (esophageal pressure measurement) not used in routine testing — which is a large part of why UARS gets missed.

How UARS Differs From OSA

The two conditions sit on a spectrum of sleep-disordered breathing, and researchers still debate whether they're truly distinct or two ends of the same continuum, but several patterns tend to separate them. UARS patients are typically younger and non-obese, and unlike OSA — which is roughly twice as common in men — UARS doesn't show a strong gender skew. Where OSA is closely associated with obesity and hypertension, patients with UARS are more often normal-weight and, in a meaningful subset, actually run toward low blood pressure rather than high. And where excessive daytime sleepiness is the hallmark OSA complaint, adult UARS patients more often describe daytime fatigue, plus a cluster of less obviously "sleep-related" complaints: chronic insomnia (both trouble falling asleep and trouble staying asleep), cold hands and feet, lightheadedness on standing, and non-specific somatic symptoms like headache and irritable-bowel-type complaints that can closely resemble functional somatic syndromes such as fibromyalgia or chronic fatigue syndrome. Because of this overlap, UARS is sometimes misattributed entirely to one of those other diagnoses rather than recognized as a sleep-disordered-breathing problem in its own right.

Why the History and Exam Alone Aren't Enough — But Still Matter

It's worth being upfront about a broader limitation that applies to sleep-disordered breathing generally, not just UARS: in a study of nearly 600 patients, a clinician's subjective impression from history and physical exam alone correctly identified OSA only about half the time, with roughly 60% sensitivity and 63% specificity. That's exactly why a sleep study, not a symptom checklist, remains the diagnostic gold standard, and why it's the only reliable way to distinguish OSA from UARS. But the exam isn't useless — it's what determines who should be referred for that testing in the first place, and certain physical findings meaningfully raise or lower suspicion. Increased neck circumference is one of the more reliable predictors identified for OSA specifically, with one landmark study finding a measurement above roughly 40 cm associated with about 93% specificity, and a validated model combining oral cavity measurements with body mass index and neck circumference improving prediction further. UARS patients, being typically non-obese, often don't show this particular marker as strongly — which is part of why relying on obesity-associated signs alone risks missing them entirely.

Where a Dental Airway Exam Fits In

The hallmark anatomic finding shared by both OSA and UARS is a crowded upper airway, and several of the physical features that produce that crowding are exactly what a dental exam is positioned to catch: a retruded lower jaw, a high-arched hard palate, dental crowding or malocclusion, and a significant dental overjet (front teeth extending well beyond the lower teeth), which is itself a sign of an underlying jaw-position issue. None of these findings diagnose UARS or OSA on their own — only a sleep study can do that — but they're the kind of anatomic red flags that can prompt a referral for sleep testing in a patient who might not otherwise have connected daytime fatigue or insomnia to their breathing during sleep. This is particularly relevant for UARS, since the typical patient — young, non-obese, more likely to report fatigue and insomnia than obvious sleepiness — doesn't fit the profile most people (including some clinicians) associate with a breathing-related sleep disorder.

Sleep-Disordered Breathing Presents Differently in Women

Underrecognition isn't unique to UARS. Sleep-disordered breathing was studied almost exclusively in men for years, and women with confirmed OSA or UARS often report a different symptom pattern — insomnia, fatigue, morning headache, mood changes — rather than the loud snoring and witnessed pauses most associated with the condition, which has historically led to longer delays before diagnosis in women compared to age-matched men. If typical sleepiness-and-snoring symptoms don't fit but fatigue, insomnia, or other non-specific complaints do, that's still worth raising rather than dismissing.

An Honest Limitation

Whether UARS should be considered a fully separate diagnosis or simply a milder point on the same spectrum as OSA remains genuinely debated in the sleep medicine field, and its prevalence in the general population isn't well established. The more clinically useful takeaway isn't resolving that debate — it's recognizing that a normal-looking sleep study doesn't automatically rule out a breathing-related explanation for unexplained daytime symptoms, particularly in a younger, non-obese patient with a crowded airway on exam.

If you have persistent daytime fatigue or insomnia and a prior sleep evaluation came back reassuring, it may still be worth a conversation about your airway anatomy — that's exactly the kind of case where a dental sleep evaluation and a physician referral work together rather than either one alone.