Your Sleep Study Can Be Normal and Still Miss This Diagnosis
What upper airway resistance syndrome is, why standard sleep studies miss it, and what specific test resolves the question
Medical disclaimer. This page is for information only. It does not replace evaluation by a qualified physician. If you have symptoms of a sleep disorder, see a sleep medicine specialist or pulmonologist for assessment. Do not start or stop any treatment based on this article alone.
By Dr. Pradyut Waghray, MBBS, MD, FRCP (London), FCCP, FAMS, Senior Pulmonologist, Respire Airway Clinics. Last reviewed: May 2026.
A sleep study that comes back normal does not rule out a sleep-related breathing disorder. For patients with upper airway resistance syndrome, the apnea-hypopnea index, or AHI, the headline number on most sleep reports, stays low. UARS produces arousals through increased airway resistance, not through the complete or partial collapses that AHI counts. The arousals are real. The fatigue is real. The standard scoring simply does not capture them.
If your sleep study came back normal but you are still exhausted all day, this is the condition most often missed. In our clinic, we see patients who have had one or two negative sleep studies and are still presenting with severe daytime fatigue and unrefreshing sleep. When we request explicit RERA scoring on their polysomnography, which many labs do not report by default, UARS is frequently identified.
What Is UARS, and How Is It Different From Sleep Apnea?
Upper airway resistance syndrome is a sleep-related breathing disorder defined by repeated arousals from sleep caused by rising effort to breathe through a partially narrowed upper airway. The airway never fully collapses. Oxygen levels rarely drop in any meaningful way. The patient is being woken, often hundreds of times a night, by their own respiratory effort, not by an apnea or hypopnea.
This is not a milder version of obstructive sleep apnea. It is a different event type. In OSA, the airway collapses fully or partially, oxygen falls, and the body arouses to restart breathing. In UARS, the airway narrows, resistance rises, the brain arouses to overcome the resistance, and the breath continues without ever meeting the criteria for an apnea or hypopnea. UARS was first described by Christian Guilleminault and colleagues at Stanford University in CHEST, 1993, in a series of patients with daytime sleepiness, normal AHI values, and abnormal esophageal pressure readings.
What Is a RERA?
A RERA, or Respiratory Effort-Related Arousal, is the diagnostic event that defines UARS. It is a sequence of breaths with progressively increasing effort that ends in an arousal from sleep, where the breaths do not meet the criteria for either an apnea or a hypopnea. RERAs are typically detected on nasal cannula pressure tracings, which show subtle flattening of the inspiratory flow signal, and on EEG, which records the arousal itself.
What Is the Respiratory Disturbance Index?
The respiratory disturbance index, or RDI, is the per-hour count of apneas, hypopneas, and RERAs combined. The AHI counts only apneas and hypopneas. A patient with an AHI of 3, which is in the normal range, can have an RDI of 15, which is in the moderate disease range, if their event burden is mostly RERAs. UARS is the diagnosis when AHI is low but RDI is elevated and the patient is symptomatic.
Symptoms of UARS
The symptoms overlap with OSA, but the pattern is different. UARS patients more often report insomnia and unrefreshing sleep than the loud snoring and witnessed apneas that point to classic OSA. They feel tired, not sleepy. Many describe the experience as “I feel like I’m not sleeping even when I am.”
UARS is also strongly associated with autonomic dysfunction, including orthostatic intolerance and a higher reported prevalence of conditions like IBS, chronic headache, and unexplained chronic fatigue (Guilleminault et al., CHEST 1993; Pépin et al., PMC4608900, 2015 review). Witnessed apneas and gasping are usually absent. If your partner has never noticed you stop breathing but you wake unrefreshed every morning, UARS belongs on the differential. For a broader symptom comparison, see our page on sleep apnea symptoms.
Why UARS Is More Common in Women and Younger Patients
UARS skews younger and more female than classic OSA. The patients are often lean, in their thirties or forties, with normal or low body-mass index, and frequently with narrow dental arches, high-arched palates, or a history of orthodontic crowding. This anatomy creates airway resistance without producing the soft-tissue collapse that defines OSA in heavier, older patients.
Why UARS Gets Missed on Standard Sleep Studies
The reason UARS gets missed is procedural, not clinical. Under the American Academy of Sleep Medicine, or AASM, scoring rules, RERA scoring is designated as optional, not required, for adult polysomnography reports (AASM Manual for the Scoring of Sleep and Associated Events, current edition). Many sleep laboratories therefore do not score RERAs at all. The report comes back with an AHI in the normal range, no mention of RERAs, no RDI calculated, and the patient is told their sleep study is normal.
If you have had a sleep study and the report does not mention RERAs or RDI, the test cannot have ruled out UARS. It was not looking for it. This is not the same as a falsely negative test. It is an incomplete test for this specific question.
What to Ask Your Doctor for Instead of, or in Addition to, AHI
If you suspect UARS, request three specific things before booking a repeat study:
- 1.A full Level 1 in-laboratory polysomnography, not a home sleep test.
- 2.Explicit RERA scoring, with RDI reported alongside AHI.
- 3.A nasal cannula pressure signal included in the recording montage, since this is the standard non-invasive method for detecting the inspiratory flow flattening that marks a RERA.
Without all three, a normal result does not rule out UARS.
How UARS Is Properly Diagnosed
Full Level 1 polysomnography, performed in a sleep laboratory with technologist attendance, is the required test. The recording must include EEG to detect arousals, a nasal cannula pressure transducer to detect flow limitation, respiratory effort belts, oximetry, and ECG. RERAs are scored from the combination of progressive flow flattening on the nasal pressure signal followed by an EEG arousal.
A home sleep study in Hyderabad, which is a Level 3 test, cannot diagnose UARS. Home tests do not record EEG, which means arousals cannot be detected, which means RERAs cannot be scored. Home studies are appropriate for evaluating moderate to severe OSA in an otherwise typical patient. They are the wrong test if UARS is on the differential. The broader workflow is covered in how sleep apnea is diagnosed; the UARS-specific requirements are stricter.
Esophageal manometry, the measurement of intra-thoracic pressure swings during breathing, is the historical gold standard for confirming increased respiratory effort during sleep and was the technique used in the original Stanford UARS papers. It is rarely performed in routine practice, in India or elsewhere, because nasal pressure cannula recordings paired with EEG arousal scoring give acceptable diagnostic yield with far less patient burden.
What the Sleep Study Report Should Include
A UARS-capable sleep study report should explicitly state:
If your existing report contains only AHI and a brief oximetry summary, the lab did not score for UARS, regardless of the conclusion line.
Treatment for UARS
Treatment for UARS largely mirrors treatment for OSA. Continuous positive airway pressure is first-line, and most patients respond when correctly titrated. The clinical detail that matters is pressure selection: because UARS is driven by inspiratory flow limitation rather than airway collapse, the pressures that abolish RERAs are often closer to those used for moderate OSA than the low pressures suggested by a low AHI alone. Many UARS patients are more comfortable on BiPAP, where a higher inspiratory pressure is paired with a lower expiratory pressure, than on fixed CPAP (Pépin et al., PMC4608900, 2015).
CPAP therapy or BiPAP
Auto-titrating CPAP is first-line. BiPAP where flow limitation persists at conventional CPAP pressures. Pressure targets for UARS are often higher than a low AHI suggests.
Mandibular advancement oral appliance
For patients with mild RDI elevation or CPAP intolerance. Fitted by a dentist with sleep medicine experience.
ENT surgical correction
Septoplasty or turbinate reduction where nasal resistance is the dominant anatomical factor contributing to airway narrowing.
Myofunctional therapy and lifestyle measures
Adjuncts rather than primary treatment. Weight-neutral approaches relevant given the lean UARS demographic.
Self-limiting note: UARS in a patient with significant cardiovascular comorbidity, uncontrolled hypertension, or known heart failure requires specialist evaluation before any positive airway pressure therapy is started. Pressure titration in these patients is not a primary-care or sleep-lab decision in isolation. The full menu of sleep apnea treatment options applies here, but the pressure targets differ.
What If CPAP Is Not Tolerated?
A meaningful subset of UARS patients struggle with CPAP at first. The reasons are usually fixable: nasal obstruction that has not been addressed, a pressure setting that is too low and is failing to abolish RERAs, or a mask leak. A formal review with a sleep physician, with re-titration where indicated, resolves most early intolerance. If positive airway pressure remains untolerated after a fair trial, a mandibular advancement device, fitted by a dentist with sleep medicine experience, is a reasonable second-line choice in well-selected patients with mild to moderate RDI.
Who Is Most Likely to Have UARS?
UARS is more common in women than men, more common in younger adults than in older adults, and more common in lean patients than in heavier patients. This is the opposite demographic profile to classic OSA. A typical UARS patient in our clinic is a thirty-five to forty-five year-old woman, with a normal BMI, a long history of insomnia and fatigue that has been attributed to stress or anxiety, and a family history of dental crowding or orthodontic work.
Autonomic features point further toward UARS: cold extremities, lightheadedness on standing, IBS-pattern bowel symptoms, low resting blood pressure. If you have been told your symptoms are psychological and your sleep study was normal, the missing test is a polysomnography with explicit RERA scoring.
Frequently Asked Questions
Can UARS cause severe fatigue even if my sleep study was normal?
Yes. A standard sleep study reports the AHI, which counts only apneas and hypopneas. UARS produces RERAs, which most laboratories do not score by default because RERA scoring is designated optional under AASM rules. A patient with a normal AHI can still have a clinically significant RDI driven by RERAs, and this is sufficient to cause severe daytime fatigue and unrefreshing sleep.
Is upper airway resistance syndrome the same as sleep apnea?
No. UARS and obstructive sleep apnea are distinct event types. In OSA the airway collapses fully or partially and oxygen falls. In UARS the airway narrows and respiratory effort rises, the brain arouses to overcome the resistance, and the breath continues without meeting apnea or hypopnea criteria. UARS is not a mild form of OSA. It is a different mechanism on the same anatomical spectrum.
Can a home sleep test diagnose upper airway resistance syndrome?
No. Home sleep tests do not record EEG, which is required to detect the arousals that define a RERA. Without EEG, RERAs cannot be scored, and UARS cannot be confirmed or excluded. Diagnosis of UARS requires full Level 1 in-laboratory polysomnography with nasal pressure cannula and explicit RERA scoring.
What is the difference between AHI and RDI?
The apnea-hypopnea index counts apneas and hypopneas per hour of sleep. The respiratory disturbance index counts apneas, hypopneas, and RERAs per hour. RDI is always equal to or higher than AHI. UARS is the diagnosis when AHI is low, often below 5, but RDI is elevated and the patient is symptomatic.
How do you treat upper airway resistance syndrome?
First-line treatment is positive airway pressure, usually auto-titrating CPAP or BiPAP, with pressures chosen to abolish RERAs rather than only apneas. Mandibular advancement oral appliances are an option in mild RDI or where CPAP is not tolerated. ENT surgical correction of nasal obstruction is appropriate where nasal resistance is the dominant anatomical contributor. Outcomes are best when pressure titration is supervised by a sleep physician with experience in UARS specifically.
Is UARS more common in women?
Yes. UARS skews female, younger, and leaner than classic OSA. The reasons are partly anatomical, including narrower dental arches and higher-arched palates, and partly hormonal. Women presenting with insomnia, daytime fatigue, and normal sleep study results, often with a label of anxiety or stress, are a group in whom UARS is frequently identified once RERA scoring is performed.
References
- Guilleminault C, Stoohs R, Clerk A, Cetel M, Maistros P. A cause of excessive daytime sleepiness: the upper airway resistance syndrome. CHEST. 1993;104(3):781-787.
- Berry RB, et al. The AASM Manual for the Scoring of Sleep and Associated Events: Rules, Terminology and Technical Specifications. American Academy of Sleep Medicine. RERA scoring is designated as an optional rule for adult polysomnography.
- Pépin JL, Guillot M, Tamisier R, Lévy P. The upper airway resistance syndrome. Respiration. 2015. PMC4608900.
Get the Right Sleep Study
UARS is not a diagnosis patients usually receive without asking the right question. If your sleep study came back normal and you are still exhausted, the next step is a polysomnography that explicitly scores RERAs and reports RDI alongside AHI.
Book a sleep assessment at our Basheer Bagh or Jubilee Hills clinic. Where RERA scoring is clinically indicated, we request it explicitly in our PSG reports. It is not optional in our protocol.