Understanding obstructive sleep apnea (OSA) Causes, risks, diagnosis, and treatment

Diagnosis begins with an assessment of symptoms, best captured by patient-reported outcome measures such as the Epworth Sleepiness Scale. That is followed by a sleep study (polysomnography), done either in a lab (attended) or at home. Your doctor helps determine which is appropriate; often a home study is performed first, with an in-lab study to follow if needed.

Most patients arrive with a sleep study, sometimes years old, and a list of treatments that did not work. We start with the story: when did the symptoms begin, what does sleep look like for you and your partner, what has been tried, and what has changed over time. The exam covers the whole airway from the nose down to the throat, including upper and lower jaw position and how the teeth fit together. A nasal endoscopy is often part of the visit because the back of the nose and the soft palate cannot be assessed from the outside. By the end, we usually have a working sense of where in the airway the problem is and what additional testing makes sense.

Bring whatever sleep studies, imaging, and orthodontic records you have. The more we can see, the more useful the visit.

It depends on what we are trying to learn. A home sleep test (HSAT) is a simple overnight recording of breathing, oxygen, and heart rate done in your own bed. It is convenient, accurate enough for most screening, and nearly every insurance plan covers it. The limitation is that it cannot tell you anything about sleep stages, arousals, or central events.

An in-lab polysomnogram (PSG) measures all of those, plus brain activity. It is the right test when symptoms do not match the home study, when the story includes insomnia or fragmented sleep, when central apnea is suspected, or when we are checking treatment response after surgery. For a young woman who feels exhausted and was told her home study was normal, an in-lab study often tells a different story.

A normal home study does not always mean normal sleep.

These are the three numbers that drive most clinical decisions about sleep apnea, and they measure different things.

AHI counts apneas (full breathing pauses) and hypopneas (partial reductions with at least a 3 or 4 percent oxygen drop) per hour of sleep. It is the metric most insurance companies use to decide coverage.

RDI is broader. It counts apneas, hypopneas, and respiratory effort-related arousals, where breathing did not collapse fully but was disrupted enough to fragment sleep. RDI often reflects how a patient feels during the day better than AHI does.

ODI counts oxygen desaturations per hour. It captures what the breathing events did to oxygen supply, which is what most directly drives cardiovascular risk over time.

The three numbers can disagree. A patient with a "normal" AHI of 4 can still have an RDI of 25 and feel exhausted, because their airway is fragmenting sleep without collapsing fully. This pattern is more common in women and is one of several reasons the standard scoring criteria can underestimate disease severity (see 2025 paper).

DISE is a short procedure performed under sedation that mimics natural sleep. While the patient is in light sleep, a flexible scope shows us where the airway collapses and how. The classic patterns are at the soft palate, the lateral pharyngeal walls, the tongue base, and the epiglottis. Without this information, surgical planning is mostly guesswork.

When a patient is already using CPAP, even partially, Dr. Liu prefers to bring the machine into the DISE itself. Dr. Liu and Dr. Carlos Torre published this approach in 2017 (see 2017 paper). CPAP behaves differently from patient to patient under direct visualization. In some, the prescribed pressure cleanly stents the whole airway open. In others, the velum or tongue base does not lift away from the posterior wall, which explains why the patient feels the mask working at the nose but still has residual events through the night. The same logic applies to oral appliances. If a patient already wears a mandibular advancement device, doing DISE with the appliance in place tells us whether it is actually repositioning the tongue and stabilizing the palate, or just shifting things at the level of the teeth. The endoscopy tells us what the sleep study cannot.

The collapse patterns then drive the rest of treatment. DISE tells us whether the soft palate collapses concentrically or anteroposteriorly, which determines whether Inspire (hypoglossal nerve stimulation) is an option. It tells us whether tongue base collapse is the dominant pattern, and whether the lateral pharyngeal walls are falling in. Our 14-center study showed that lateral wall and tongue base obstruction are the strongest anatomical predictors of surgical outcome (see 2019 multicenter study). They are also the patterns that soft tissue surgery has the hardest time fixing on its own.

DISE also helps explain why certain surgeries work, and why some patients should be steered toward MMA over Inspire. We published in 2015 that the largest measurable change after maxillomandibular advancement is a reduction in lateral pharyngeal wall collapsibility (see 2015 paper). The advancement pulls the soft tissue scaffolding outward and stabilizes the lateral walls of the throat. This is one major reason MMA can work for patients with complete concentric collapse at the soft palate, where Inspire alone is contraindicated. A follow-up study combining DISE with computational fluid dynamics confirmed the mechanism (see 2016 paper): the patients whose AHI dropped the most after MMA were the ones whose lateral wall stability and retropalatal airflow had normalized.

For patients turned down for Inspire because of complete concentric collapse, DISE also opens another door. Our 2020 paper showed that a tissue-sparing palate procedure, what we call preservation pharyngoplasty, can convert the concentric pattern into one that is Inspire-eligible (see 2020 paper). The point is to make Inspire possible for patients who would otherwise have been told no, then layer the two for a more durable response.

For most patients considering surgery beyond a simple nasal procedure, DISE is part of the workup. In our practice, DISE is used as a true diagnostic tool. It shapes which treatment is offered, rather than confirming one already chosen. Surgeons understandably gravitate toward what they perform, which means DISE findings pointing toward a different option can sometimes be set aside. Because we offer the full range of procedures across the revised Riley-Powell-Liu Stanford algorithm (see 2020 chapter), the endoscopy is read for what it shows, and the patient is matched to the procedure that fits their anatomy.

OSA is characterized by reduced airflow during sleep. Even a slight reduction, though unnoticeable to the sleeper, significantly disrupts sleep quality and causes daytime sleepiness. Persistent reduction leads to loss of oxygenation, which in the short term causes disruptive waking, and over the long term worsens arrhythmia, hypertension, and diabetes, with significant implications for mental health as well.

In children: nasal allergies, enlarged adenoids and tonsils, and under-development of the jaws. Notably, younger children with OSA can be underweight rather than obese.

In adults: obesity becomes a larger factor, with fat accumulating in the airway and in the tongue, and can also cause hypoventilation. With age the airway lengthens, adding redundancy and collapsibility of the soft palate and side walls, while the dilator muscles function less well during sleep.

The single most underappreciated finding in sleep medicine is that breathing through your nose during sleep is fundamentally different from breathing through your mouth. Nasal breathing filters and humidifies air, generates nitric oxide that opens the lower airways, and stabilizes the upper airway during sleep. Mouth breathing during sleep collapses the soft palate, dries out tissues, and contributes to snoring and apnea even in patients on CPAP.

There is a simple 2x2 way to think about it: nasal versus mouth breathing, awake versus asleep. Most patients can manage nasal breathing while awake. Restoring nasal breathing during sleep is where most of our work happens. That is why so many of the procedures across these life stages, from rapid palatal expansion in children to DOME in adults, target the nasal floor and the upper jaw. When those structures are right, they optimize sleep breathing.

Further reading: A 2x2 Matrix: Nasal vs Mouth Breathing, Awake vs Asleep

Snoring in a child is not normal. In most adults, snoring is annoying. In a child, it can be the first visible sign of sleep-disordered breathing. The other clues parents miss are bedwetting after age 6, restless or sweaty sleep, mouth open during the day, dark circles under the eyes, and behavior issues that get labeled as ADHD when the underlying problem is fragmented sleep. Catching this early gives us the most options, because the upper airway and its support (facial skeleton) are still developing.

For some children, yes. For others, the tonsils and adenoids are only part of the picture. The published data on tonsillectomy and adenoidectomy shows a meaningful residual rate of sleep-disordered breathing after surgery, especially in children with a narrow upper jaw, a high-arched palate, a tongue tie, or chronic nasal obstruction. We published work showing that rapid palatal expansion can normalize the size of adenoids and tonsils in some children (see 2022 study), which suggests the airway and the facial skeleton are deeply linked. The restoration of healthy breathing patterns requires consideration of both soft and skeletal tissue.

Rapid palatal expansion (RPE) utilizes a distractor that widens the upper jaw over weeks. In a young child, the bone in the roof of the mouth has not yet fused. The distractor is secured to the teeth. As the distractor is turned, the upper jaw growth occurs laterally with bone formation along the mid-palatal suture. Wider jaw means wider nasal floor, more room for the tongue, and easier nasal breathing particularly during sleep. Among published treatments for pediatric sleep-disordered breathing, expansion is among the most effective at improving nighttime oxygen levels (see 2020 systematic review), and follow-up studies suggest the benefits hold over many years.

Further reading: A 2x2 Matrix: Nasal vs Mouth Breathing, Awake vs Asleep

Think of it as physical therapy for the mouth and face. A trained therapist teaches the tongue to rest against the palate, the lips to stay closed, and breathing to move through the nose during the day. These habits sound simple, but they shape how the upper jaw grows. Myofunctional therapy works best in combination with expansion and, when indicated, release of a tongue tie. Our 348-case series with frenuloplasty plus myofunctional therapy supports this combined approach (see 2019 paper).

It can. A restricted tongue often sits low in the mouth instead of resting against the palate, and the palate is partly shaped by tongue pressure during growth. Our published research in over 1,000 subjects mapped the link between restricted tongue mobility and underdeveloped upper jaws (see 2017 study). When indicated, frenuloplasty combined with myofunctional therapy is safe and effective.

Possibly, but adolescent fatigue is often blamed on hormones or screens when the real cause is poor breathing during sleep. A teenager with crowded teeth, mouth breathing, grinding at night, or persistent nasal congestion is often showing signs of an undersized airway. By late adolescence, the suture in the roof of the mouth begins to fuse, which narrows the treatment options. This stage is the last window for relatively simple correction.

This is worth pausing on. Extractions create dental room, but they can leave the upper and lower jaws too small for the tongue and the soft palate. Many of the adults we now treat for sleep apnea had four bicuspids removed as teenagers. That does not mean extractions are always wrong, but if your teenager also snores, mouth breathes, or has a high-arched palate, an airway-focused evaluation is worth considering. The suggestion of tooth extraction often means that the jaws are undersized. Since there are ways to guide jaw growth, expansion can be a viable solution to extraction.

Further reading: DOME360: A Workshop on Breathing Health & Craniofacial Development

Not necessarily, but the technique changes. In younger children, simple rapid palatal expansion works. In older adolescents, the suture has started to fuse, and more importantly, resistive forces against upper jaw expansion have increased. The advent of mini-screws, or temporary anchorage devices (TADs), can work well, starting with teenagers. Doing this with concurrent clear aligner treatment ensures an aesthetic process during and after treatment (see DOME).

Straight teeth and a healthy airway are not the same thing. Orthodontics aligns the teeth within whatever skeletal framework already exists. If the upper jaw is too narrow, the lower jaw too set back, or the nose chronically obstructed, none of those issues are fixed by braces (see 2023 paper). This is one of the most common reasons young adults find their way to our clinic.

You are the patient population that motivated much of our research. Young, healthy adults with sleep apnea usually have a structural reason for it: a narrow upper jaw, a small or set-back lower jaw, persistent nasal obstruction, or all three. CPAP fights the anatomy. Procedures like DOME (distraction osteogenesis maxillary expansion), targeted nasal surgery, and in selected cases jaw advancement, change the shape of the airway so it stops collapsing in the first place (see 2020 algorithm update).

DOME is a concept, and not just a procedure. The idea: the upper jaw and the floor of the nose share the same bone, and when that bone is widened into a proper dome shape, the nasal airway opens, the tongue gains room to rest against the palate, and breathing during sleep improves. The destination is the dome-shaped palate. The path to get there has changed over time.

We first described DOME in our 2017 paper as a surgical technique for adults whose palatal suture had already fused. It used a bone and tooth anchored expander combined with a surgical procedure to separate the maxilla, and the patient turned the expander once a day for about a month. That approach is still the right answer for some patients, particularly those with significant skeletal restriction or who need it combined with other surgery.

Today, most patients reach the same dome-shaped palate without traditional surgery. DOMEzero and DOMEmini are the next evolution of the concept: synchronized protocols that combine bone-level palatal expansion with clear aligners, so adults and children get the airway and bite benefits at the same time. This also avoids the large temporary teeth gaps (diastema) that older expansion methods, or contemporary "rapid" procedures, produced. Which path fits depends on skeletal maturity, the degree of palate constriction, and what bite correction is needed. The destination is the same. The means of getting there have become less invasive and more patient-centric.

Further reading: Aligning Maxillary Expansion with Nasal Breathing

This is one of the most common stories we hear. A septoplasty corrects the wall between the two nasal passages, but if the floor of the nose itself is too narrow, the airflow problem can persist. In our 2019 study (Williams, Liu et al), we showed in a controlled case series that patients with persistent nasal obstruction after primary septoplasty often share the same underlying anatomy: a narrow, high-arched hard palate with reduced maxillary width near the internal nasal valve (see 2019 study). Our follow-up work then showed that DOME can resolve persistent nasal obstruction even after a previous septoplasty in these patients (see 2022 study). The septum is often not the whole story.

The airway and the face share the same skeleton, so changes to one affect the other. Most patients describe the changes as positive. Patient-reported outcomes after MMA support this (see 2022 paper). The goal is bite, breathing, and beauty together, not one traded for the other.

Maybe not. Up to 90 percent of women with sleep-disordered breathing are undiagnosed, partly because the standard diagnostic parameters were built around male presentations. Women often present with insomnia, mood changes, fatigue, and morning headaches rather than loud snoring. Average AHI in women is around 33 percent lower than in men with similar symptoms. At the same time, women are 3 times more likely to be on multiple antidepressant and anti-anxiety medications (see 2025 paper). If you do not feel rested and the basic numbers look normal, a more careful evaluation is reasonable.

You have real options, and the right one depends on a careful evaluation. The diagnostic starting point is drug-induced sleep endoscopy (DISE), which lets us see exactly where and how your airway collapses during sleep. From there, the options range from nasal procedures, palate surgery, tongue procedures, hypoglossal nerve stimulation (Inspire), to maxillomandibular advancement (MMA) for moderate to severe disease. Our 14-center DISE study showed that lateral wall and tongue collapse patterns are the most difficult collapse patterns for soft tissue surgery to address (see 2019 multicenter study). The advent of Inspire (hypoglossal nerve stimulation) and improved MMA, which stabilizes the velum and lateral pharyngeal walls effectively, addresses the shortcomings of soft tissue surgery.

Inspire (hypoglossal nerve stimulation) works well for a specific patient profile: AHI between 15 and 65, BMI 32 or lower, and an airway that does not collapse in a complete concentric pattern at the soft palate. The FDA-expanded criteria now reach 100 events per hour and BMI of 40 kg/m², but the original narrower criteria produced more predictable results. Whether your collapse pattern qualifies is determined by drug-induced sleep endoscopy. Published 5-year data shows roughly 75 percent of patients have a sustained response. Our group has published on extending Inspire eligibility to patients who would otherwise be turned down due to OSA severity or anatomic restrictions, by first treating the obstructive site with palate, expansion, or jaw surgery before HGNS. Patients on this pathway do better than matched HGNS-only patients despite starting from more severe disease (see 2024 paper).

Yes. For patients who have already had jaw advancement and still have residual apnea, Inspire is a reasonable next step, and we published one of the early reports on this combination (see 2019 paper). More recent work shows that layering Inspire with other targeted procedures, sometimes called multilevel surgery, produces greater reductions in apnea than Inspire alone (see 2023 study). Inspire is not always a stand-alone solution. The best results often come from combining it with other procedures matched to where your airway actually collapses.

Further reading: HGNS Inspire(s) Next Gen Surgeons

While the name of soft palate surgery to treat OSA is known as uvulopalatopharyngoplasty (UPPP), there are many different variants of how the procedure is performed. Older UPPP removed significant amounts of soft tissue including the uvula, and is associated with long-term changes in speech and swallowing. Most contemporary soft palate surgery, where we call ours preservation pharyngoplasty, is built on a tissue-sparing technique developed at Stanford. It suspends and strengthens the soft palate muscles instead of removing them, with equivalent or better airway opening and far fewer side effects. Published 15-year follow-up data shows the benefit is sustained over time.

Preservation pharyngoplasty also matters for Inspire candidacy. Some patients are turned down for Inspire because their soft palate collapses in a complete concentric pattern. Our published work shows that preservation pharyngoplasty can reverse complete concentric collapse to a pattern that is Inspire-eligible (see 2020 paper), opening nerve stimulation as an option for patients who would otherwise be told no.

Classically, the treatment of dentofacial deformity (malocclusion, jaw position discrepancy, with functional deficits involving chewing) is called orthognathic surgery. It literally means "straightening the jaws." When Dr. Liu's mentors, Dr. Robert Riley and Dr. Nelson Powell, began to use maxillofacial surgery to treat upper airway collapse during sleep, they advanced the upper and lower jaw bones, and made maxillomandibular advancement (MMA) the most effective surgical treatment for OSA.

In reality, patients often present with some degree of DFD and OSA together. The best way to think about the terminology: orthognathic surgery is ideally planned with airway considerations (for example, avoiding setting back the jaw bones in a way that collapses the airway), and MMA surgery should consider orthognathic principles of facial proportion and symmetry. Looked at through the lens of optimizing the three functions of bite, breathing, and beauty, orthognathic and MMA surgery are not separate entities.

Often, yes. Dentofacial deformity (DFD), meaning a jaw that did not develop into a balanced position, and obstructive sleep apnea (OSA) overlap more than most patients realize. A set-back lower jaw, a constricted upper jaw, or a class II or class III bite can be the underlying reason the airway is undersized in the first place. This is why we no longer treat orthognathic surgery and MMA as two separate conversations.

In our practice, every skeletal surgery is designed around three goals at once: bite, breathing, and beauty. Our 2023 study showed that MMA produces near-equivalent improvements in apnea severity in patients with class II versus class III bites, which means the airway benefit holds across very different starting anatomies (see 2023 study). Several of our recent book chapters detail how this integrated planning works in practice (see chapters on skeletal surgery for OSA). The patients who benefit most from this thinking are the ones who would otherwise have had two operations, in two specialties, with the airway as an afterthought.

Maxillomandibular advancement moves both jaws forward together, opening the entire airway from the nose down to the throat. Across many published series, it has the highest surgical success and cure rates of any single sleep apnea procedure (see 2018 review). The technique we use is the result of more than 30 years of refinement at Stanford with Dr. Robert Riley and Dr. Nelson Powell, now updated with virtual surgical planning, 3D-printed guides and plates, and facial balance considerations.

Further reading: World Sleep Congress 2025: Inside the First Sleep Surgery Cadaver Workshop

Yes. Untreated sleep apnea is associated with hypertension, atrial fibrillation, carotid plaque, and heart failure. Carotid imaging in sleep apnea patients showed a strong association between severity and arterial inflammation (see 2019 study). Treating the breathing problem is part of treating the cardiovascular problem.

Most sleep apnea surgeries are covered when medically necessary and when you have documented intolerance or failure of CPAP. Coverage depends on your specific plan, your AHI, and the procedure proposed.

Age alone is not a contraindication. Our published work using a national surgical database (NSQIP) of more than 2,200 patients showed that those over 65 do face higher complication rates for major sleep surgery (see 2017 study), so the conversation usually shifts toward less invasive options. Inspire stimulation is often a good fit at this stage. Targeted nasal procedures, or tissue-preserving palate procedures like preservation pharyngoplasty, combined with optimal medical care, can also meaningfully improve sleep without the recovery of larger surgery.

Possibly. The connection between untreated sleep apnea and cognitive decline is becoming clearer in the research. Treating breathing during sleep does not reverse all cognitive change, but improving oxygenation and sleep quality often produces noticeable gains in alertness, mood, and daily function.

This is one of the most common ways patients first reach our clinic, brought by a worried partner. Home sleep testing is now simple, accurate enough for screening, and covered by most insurance plans. The bigger barrier is usually the conversation, not the test itself. Coming in for a consultation as a couple often helps move things forward.