What Is Sleep Apnea?
Sleep apnea is a sleep disorder characterized by repeated episodes during sleep where breathing stops (apneas) or is significantly reduced (hypopneas). These events typically last 10–30 seconds but can extend longer. Each event causes brief arousal from sleep as the brain responds to the oxygen drop, even if the person doesn't consciously awaken.
Moderate to severe sleep apnea produces dozens to hundreds of these arousals per night, profoundly fragmenting sleep architecture and preventing adequate deep and REM sleep. The result is excessive daytime sleepiness, cognitive impairment, mood disturbance, and — over time — serious cardiovascular, metabolic, and neurological health consequences.
Types of Sleep Apnea
Obstructive Sleep Apnea (OSA)
By far the most common type (accounts for ~90% of sleep apnea). In OSA, the muscles of the throat and upper airway relax during sleep, causing the soft tissues to collapse and partially or completely block the airway. Breathing effort continues (the chest and abdomen still try to breathe) but airflow is obstructed. The brain senses oxygen desaturation and briefly arouses the person to restore airway tone and breathing.
Central Sleep Apnea (CSA)
In CSA, breathing pauses because the brain doesn't send the appropriate signals to the breathing muscles — not because of airway obstruction. There is no breathing effort during the apnea. CSA is less common and often associated with heart failure, stroke, high altitude, or opioid medication use. It may also occur as treatment-emergent CSA in CPAP users (formerly called complex sleep apnea).
Complex (Mixed) Sleep Apnea
A combination of obstructive and central elements, sometimes emerging when OSA is treated with CPAP and underlying central events become apparent. Treated with adaptive servoventilation (ASV) or BiPAP in appropriate candidates.
Symptoms of Sleep Apnea
- Loud, chronic snoring (especially if you snore and also feel unrefreshed in the morning)
- Witnessed apneas — partner observes you stopping breathing
- Gasping or choking sounds during sleep
- Waking with a headache or dry mouth
- Excessive daytime sleepiness despite adequate sleep time
- Falling asleep unintentionally during low-stimulation activities
- Cognitive impairment: memory, concentration, attention difficulties
- Mood disturbances, irritability, depression
- Frequent nighttime urination (nocturia)
- High blood pressure, especially difficult to control
Many people with sleep apnea are unaware of their condition — they snore and feel sleepy but don't realize their sleep is being disrupted hundreds of times per night. Partners are often the first to notice the apnea episodes.
Risk Factors
| Risk Factor | Effect |
|---|---|
| Obesity (BMI >30) | Fat deposits around the neck and upper airway narrow the airway. OSA risk increases substantially with BMI. |
| Neck circumference | >17 inches in men, >16 inches in women associated with significantly higher risk |
| Male sex | Men are 2–3x more likely than premenopausal women; risk equalizes after menopause |
| Age | Risk increases with age; peak prevalence in 40s–60s |
| Anatomical features | Narrow jaw, large tonsils/adenoids, deviated nasal septum, retrognathia (small chin) |
| Alcohol before bed | Relaxes upper airway muscles, dramatically worsening OSA |
| Sedative medications | Benzodiazepines and muscle relaxants worsen airway tone |
| Smoking | Causes airway inflammation, increasing OSA risk |
| Family history | Genetic component to airway anatomy and neuromuscular control |
| Hypothyroidism, acromegaly | Both cause soft tissue changes that narrow the airway |
The Apnea-Hypopnea Index (AHI): Severity Classification
The primary metric used to diagnose and classify sleep apnea severity is the Apnea-Hypopnea Index (AHI) — the average number of apneas and hypopneas per hour of sleep, measured during a sleep study.
| AHI | Severity | Notes |
|---|---|---|
| 0–4 events/hour | Normal | Some snoring may occur without significant sleep disruption |
| 5–14 events/hour | Mild OSA | Symptoms may be minimal; treatment decision based on symptoms and comorbidities |
| 15–29 events/hour | Moderate OSA | Treatment generally recommended; significant symptom burden |
| 30+ events/hour | Severe OSA | Treatment strongly indicated; high health risk if untreated |
AHI alone doesn't capture the full picture — oxygen desaturation level (how far oxygen drops during events), sleep fragmentation degree, and symptom burden all factor into treatment urgency. Some people with moderate AHI have minimal symptoms; others with the same AHI are severely impaired.
Diagnosis: Home Sleep Test vs. Lab Polysomnography
Home Sleep Apnea Test (HSAT)
A simplified, portable monitoring device worn at home overnight. Typically measures airflow, breathing effort, oxygen saturation, and heart rate. Advantages: lower cost, no need to sleep in a lab, more natural sleep environment. Limitations: cannot measure brain activity (sleep staging), misses positional and stage-specific OSA patterns, may underestimate severity (patients often sleep less well with the device and miss some REM-related events). Appropriate for: suspected uncomplicated moderate-to-severe OSA in otherwise healthy adults.
In-Lab Polysomnography (PSG)
The gold standard sleep study, conducted overnight in a sleep laboratory with full monitoring including EEG (brain waves), EOG (eye movements), EMG (muscle activity), ECG (heart), airflow, breathing effort, oxygen saturation, body position, and limb movements. Provides comprehensive data on all sleep stages and the full range of sleep disorders. Advantages: complete, definitive diagnosis for complex cases. Limitations: cost, inconvenience, "first night effect" (some patients sleep differently in the lab). Recommended when: CSA is suspected, HSAT is negative but symptoms persist, comorbid sleep disorders (narcolepsy, REM behavior disorder) need evaluation, or HSAT is technically inadequate.
Treatment Options
CPAP (Continuous Positive Airway Pressure)
CPAP is the gold standard first-line treatment for moderate and severe OSA, and for symptomatic mild OSA. A CPAP machine delivers a continuous stream of pressurized air through a mask worn over the nose or nose and mouth. The positive pressure acts as a pneumatic splint, preventing the upper airway from collapsing during sleep.
- Effectiveness: When used consistently, CPAP eliminates apnea events in most patients (AHI typically reduced to <5), resolves daytime sleepiness, normalizes cardiovascular stress markers, and improves cognitive function
- Adherence: The primary limitation of CPAP is adherence — approximately 30–50% of patients use it less than the clinically recommended 4 hours/night. Mask fit, pressure comfort, claustrophobia, noise, and relationship disruption are common barriers
- Improving adherence: Mask selection (multiple styles — nasal pillows, nasal masks, full face masks), pressure ramp-up features, humidification, and consistent troubleshooting with a sleep specialist significantly improve adherence
APAP (Auto-Adjusting Positive Airway Pressure)
APAP machines automatically titrate pressure within a set range based on real-time airway conditions — increasing pressure when apneas or snoring are detected, decreasing when not needed. Generally more comfortable than fixed-pressure CPAP because pressure is lower on average. Now the standard prescription for most OSA patients.
BiPAP (Bilevel Positive Airway Pressure)
BiPAP delivers different pressures for inhalation (higher) and exhalation (lower), making exhalation easier. Indicated for patients who cannot tolerate the constant pressure of CPAP, those with high pressure requirements, and central sleep apnea. More expensive than CPAP.
Oral Appliances (Mandibular Advancement Devices — MADs)
Custom-fitted dental devices that hold the lower jaw (mandible) forward during sleep, enlarging the upper airway space and reducing collapsibility. Effective for mild-to-moderate OSA and significantly easier to tolerate and travel with than CPAP. Efficacy is generally lower than CPAP for severe OSA. Side effects include tooth soreness, jaw joint (TMJ) discomfort, and bite changes with long-term use. Must be fitted by a qualified dentist specializing in dental sleep medicine.
Positional Therapy
OSA is often position-dependent — significantly worse when sleeping on the back (supine), where gravity promotes airway collapse. Positional therapy uses devices (vibrating position alarms, special pillows, anti-snore belts) to prevent supine sleeping. Effective for "positional OSA" (AHI at least 2x higher supine than lateral) as sole therapy or supplement to other treatments.
Weight Loss
Since obesity is a major risk factor, weight loss significantly reduces OSA severity. Even a 10–15% reduction in body weight can reduce AHI by 30–50% in obese patients. Weight loss alone rarely eliminates severe OSA but can reduce it to mild levels where other treatments become effective. For patients who achieve significant weight loss through bariatric surgery, OSA can resolve completely in some cases.
Surgery
Several surgical options address specific anatomical contributors to OSA:
- Uvulopalatopharyngoplasty (UPPP): Removes excess tissue from the soft palate and throat; variable effectiveness for OSA
- Tonsillectomy/adenoidectomy: Highly effective for OSA in children with enlarged tonsils and adenoids; less commonly indicated in adults
- Maxillomandibular advancement (MMA): Surgically advances the upper and lower jaws to expand the airway; high success rates for carefully selected patients
- Nasal surgery: Corrects septal deviation or nasal polyps that contribute to mouth breathing and worsened OSA
Upper Airway Stimulation (Inspire Therapy)
A surgically implanted device that stimulates the hypoglossal nerve (which controls tongue position) in sync with breathing, preventing tongue base collapse. Approved for moderate-to-severe OSA patients who cannot tolerate CPAP. Requires specific anatomical criteria (confirmed with drug-induced sleep endoscopy). Highly effective for appropriate candidates — a significant advance in treatment options.
What to Expect at a Sleep Study
For an in-lab polysomnography: you arrive at the sleep lab in the early evening (usually 8–9 PM). A technician attaches 20+ monitoring sensors using conductive paste (they are painless and do not require needles). Sensors include EEG electrodes on the scalp, sensors around the eyes and chin, breathing sensors at the nose and mouth, a pulse oximeter on the finger, effort belts around the chest and abdomen, and EMG electrodes on the legs.
You sleep (or try to) in a private room with a camera and monitoring equipment. The technician watches your data in real time from an adjacent room and can intervene if needed (for CPAP titration in a split-night study). Most patients sleep adequately despite the setup. The study typically ends at 6–7 AM.
Results are scored by a registered polysomnographic technologist and interpreted by a board-certified sleep medicine physician. A follow-up appointment reviews findings and establishes a treatment plan — typically within 1–2 weeks.