Sleep Apnea: Causes, Symptoms, Diagnosis & Treatment

Sleep apnea is a serious sleep disorder characterized by repeated interruptions in breathing during sleep. These breathing pauses, called apneas, can last 10 seconds or longer and may occur dozens to hundreds of times per night. Each event triggers a brief arousal from sleep—often without the person's awareness—that fragments sleep architecture and reduces blood oxygen levels.

The most common form, obstructive sleep apnea (OSA), occurs when the muscles in the back of the throat relax excessively during sleep, causing the upper airway to narrow or collapse completely. This creates a physical obstruction to airflow despite continued respiratory effort. The brain detects the drop in oxygen and briefly wakes the sleeper to reopen the airway, often accompanied by a gasp or snort.

Sleep apnea affects an estimated 22 million Americans, though up to 80% of moderate-to-severe cases remain undiagnosed. It is more than a nuisance—untreated sleep apnea is associated with hypertension, heart disease, stroke, type 2 diabetes, motor vehicle accidents, and reduced life expectancy. Effective treatment exists and can dramatically improve quality of life and long-term health outcomes.

Obstructive Sleep Apnea (OSA)

The most common type, accounting for approximately 84% of cases. OSA occurs when soft tissues in the upper airway collapse during sleep. Severity is measured by the Apnea-Hypopnea Index (AHI): mild (5-15 events/hour), moderate (15-30), or severe (>30).

Central Sleep Apnea (CSA)

Less common, CSA occurs when the brain fails to send proper signals to the muscles controlling breathing. Unlike OSA, there is no physical obstruction—the airway is open, but respiratory effort is absent. CSA is associated with heart failure, stroke, opioid use, and high-altitude exposure.

Complex (Treatment-Emergent) Sleep Apnea

A combination of obstructive and central events. Some patients initially diagnosed with OSA develop central apneas after starting CPAP therapy. This condition often resolves over time but may require specialized bilevel or adaptive servo-ventilation devices.

Sleep apnea symptoms are divided into nighttime signs (often noticed by a bed partner) and daytime consequences:

Nighttime Symptoms

• Loud, chronic snoring — typically loudest when sleeping on the back
• Witnessed breathing pauses — a bed partner observes you stop breathing
• Gasping or choking episodes — waking suddenly with a sensation of suffocation
• Restless sleep — frequent position changes, tossing and turning
• Nocturia — waking multiple times to urinate
• Night sweats — unrelated to room temperature

Daytime Symptoms

• Excessive daytime sleepiness — difficulty staying alert during passive activities
• Morning headaches — dull, pressing headaches that resolve within hours
• Dry mouth or sore throat upon waking
• Difficulty concentrating — brain fog, memory problems
• Mood changes — irritability, depression, anxiety
• Decreased libido

Importantly, many people with sleep apnea are unaware of their nighttime symptoms. They may attribute daytime fatigue to aging, stress, or poor sleep habits rather than recognizing it as a sign of a treatable medical condition.

Several anatomical, demographic, and lifestyle factors increase the likelihood of developing obstructive sleep apnea:

• Excess weight: The strongest modifiable risk factor. Fat deposits around the upper airway narrow the breathing passage. A neck circumference greater than 17 inches (men) or 16 inches (women) significantly increases risk.
• Age: Risk increases with age, particularly after 40, due to decreased muscle tone in the airway.
• Male sex: Men are 2-3 times more likely to have OSA than premenopausal women. After menopause, the gender gap narrows.
• Family history: Genetic factors influencing facial structure and airway anatomy contribute to hereditary risk.
• Anatomy: Large tonsils, retrognathia (recessed jaw), macroglossia (large tongue), or a narrow palate all predispose to obstruction.
• Alcohol and sedatives: These substances relax upper airway muscles, worsening existing OSA or unmasking latent apnea.
• Smoking: Increases inflammation and fluid retention in the upper airway.
• Nasal congestion: Chronic obstruction from allergies or deviated septum increases negative inspiratory pressure.

Diagnosing sleep apnea requires objective sleep testing because symptoms alone cannot reliably determine severity or confirm the diagnosis. The diagnostic process typically follows these steps:

Clinical Evaluation

Your physician assesses symptoms, examines your upper airway anatomy, measures neck circumference, and reviews medical history. Screening questionnaires (STOP-BANG, Epworth Sleepiness Scale) help quantify risk but are not diagnostic.

Sleep Study (Polysomnography)

The gold standard for diagnosing sleep apnea. An overnight in-lab polysomnogram records brain activity, breathing, oxygen levels, heart rhythm, and body movements. The key metric is the Apnea-Hypopnea Index (AHI):

• Normal: AHI less than 5 events per hour
• Mild sleep apnea: AHI 5-15
• Moderate sleep apnea: AHI 15-30
• Severe sleep apnea: AHI greater than 30

Home Sleep Apnea Test

A portable device used at home that measures airflow, oxygen saturation, and respiratory effort. Appropriate for patients with high pre-test probability of moderate-to-severe OSA without significant comorbidities. A negative home test does not rule out sleep apnea in symptomatic patients.

Continuous Positive Airway Pressure (CPAP)

The first-line treatment for moderate-to-severe OSA. CPAP delivers pressurized air through a mask worn during sleep, acting as a pneumatic splint to keep the airway open. When used consistently, CPAP eliminates apneas, normalizes oxygen levels, reduces daytime sleepiness, and lowers cardiovascular risk.

Oral Appliance Therapy

Custom-fitted dental devices that advance the lower jaw forward during sleep, enlarging the airway space. Recommended for mild-to-moderate OSA or for patients who cannot tolerate CPAP. Fitted by a dentist specializing in dental sleep medicine.

Positional Therapy

For patients whose apnea occurs predominantly when sleeping supine (on the back), positional devices prevent back-sleeping. This may be sufficient for mild positional OSA but is rarely adequate as standalone treatment for moderate-to-severe disease.

Weight Management

Weight loss of 10-15% can significantly reduce OSA severity and may cure mild cases. Bariatric surgery has shown dramatic improvements in patients with morbid obesity and severe OSA.

Surgical Options

Various surgical procedures address specific anatomical obstructions: uvulopalatopharyngoplasty (UPPP), tonsillectomy, maxillomandibular advancement, and hypoglossal nerve stimulation (Inspire therapy). Surgery is typically considered when conservative treatments fail or specific anatomical issues are identified.

Lifestyle Modifications

• Avoid alcohol within 3 hours of bedtime
• Discontinue sedative medications when possible
• Treat nasal congestion and allergies
• Maintain consistent sleep schedule
• Elevate head of bed 30 degrees

Untreated sleep apnea carries significant health consequences beyond daytime fatigue:

• Cardiovascular disease: OSA independently increases risk of hypertension, coronary artery disease, heart failure, and atrial fibrillation due to repeated oxygen desaturations and sympathetic nervous system activation.
• Stroke: Moderate-to-severe OSA doubles stroke risk, particularly in men.
• Type 2 diabetes: Intermittent hypoxia impairs glucose metabolism and insulin sensitivity.
• Motor vehicle accidents: Drowsy driving due to untreated sleep apnea increases crash risk 2-7 times. Commercial drivers with untreated sleep apnea face mandatory treatment requirements.
• Cognitive decline: Chronic sleep fragmentation and oxygen deprivation contribute to memory problems and may accelerate dementia progression.
• Depression: The relationship between OSA and depression is bidirectional; treating OSA often improves depressive symptoms.
• Surgical risk: Patients with undiagnosed OSA face higher perioperative complications, particularly with general anesthesia.

The good news: effective treatment of sleep apnea significantly reduces these risks and often improves or resolves associated conditions, particularly hypertension and cardiac rhythm abnormalities.