Obstructive Sleep Apnea: Pathophysiology, Clinical Impact, and Evidence-Based Management

What is obstructive sleep apnea?

Obstructive sleep apnea (OSA) is the most prevalent sleep-related breathing disorder and is characterized by repeated episodes of partial or complete upper airway obstruction during sleep. These events lead to transient cessations of breathing, known as apneas, or to shallow breathing episodes, known as hypopneas. Each episode disrupts normal sleep architecture and alters blood oxygen levels.

OSA occurs when the muscles of the throat relax excessively during sleep, allowing the airway to narrow or collapse. This obstruction is intermittent and can happen dozens or even hundreds of times per night. Snoring is a common clinical sign, but not all individuals who snore have obstructive sleep apnea.

Untreated OSA is associated with significant cardiovascular, metabolic, neurocognitive, and psychosocial consequences. Because symptoms often develop gradually, many individuals remain undiagnosed for years.

Mechanisms underlying airway obstruction

During sleep, especially in rapid eye movement (REM) phases, muscle tone throughout the body decreases. In susceptible individuals, this reduction in tone affects the muscles supporting the soft palate, uvula, tongue, and lateral pharyngeal walls.

When these structures collapse inward, airflow is reduced or completely blocked. As oxygen levels fall and carbon dioxide rises, the brain briefly arouses the individual from sleep to restore airway patency. These arousals are typically so short that the person has no conscious memory of them.

This cycle of airway collapse, oxygen desaturation, and arousal may occur more than five times per hour and prevents restorative deep sleep. Over time, the repetitive physiological stress contributes to systemic disease.

Clinical manifestations

Nocturnal symptoms

Common symptoms occurring during sleep include:

• Loud, habitual snoring

• Observed pauses in breathing, often reported by a partner

• Gasping, choking, or snorting sounds

• Restless sleep

• Frequent nighttime urination

Daytime symptoms

Symptoms during waking hours reflect chronic sleep fragmentation and intermittent hypoxia:

• Excessive daytime sleepiness

• Morning headaches

• Dry mouth or sore throat upon waking

• Difficulty concentrating and impaired memory

• Mood disturbances, including irritability and depressive symptoms

• Reduced libido

• Poor work performance and increased accident risk

Many individuals with OSA are unaware that their sleep is disrupted and may underestimate the severity of their symptoms.

Risk factors

Several factors increase susceptibility to obstructive sleep apnea:

• Excess body weight, particularly central and upper airway fat deposition

• Male sex, with increased risk after menopause in women

• Advancing age

• Family history of obstructive sleep apnea

• Anatomical features such as enlarged tonsils, a narrow airway, or craniofacial abnormalities

• Chronic nasal obstruction

• Tobacco use

• Certain endocrine and metabolic disorders, including hypothyroidism and insulin resistance

OSA frequently coexists with systemic conditions such as hypertension, diabetes mellitus, cardiovascular disease, and mood disorders.

Diagnostic evaluation

Diagnosis begins with a detailed clinical history and physical examination focused on sleep patterns, daytime functioning, and risk factors. Confirmation typically requires objective sleep assessment.

Polysomnography remains the diagnostic standard and measures respiratory events, oxygen saturation, sleep stages, and arousal frequency. In selected cases, validated home sleep testing may be used.

Early diagnosis is essential, as effective treatment can significantly reduce morbidity and improve quality of life.

Therapeutic approaches

Management of obstructive sleep apnea is individualized and depends on disease severity, anatomical factors, and patient preference.

Non-invasive therapies

Positive airway pressure therapy delivers pressurized air through a mask to keep the airway open during sleep and remains the most effective treatment for moderate to severe OSA.

Oral appliances that reposition the lower jaw may be beneficial in selected patients with mild to moderate disease.

Weight reduction can significantly improve symptoms in individuals with excess body mass and may reduce disease severity.

Surgical options

Surgical intervention may be considered in patients with specific anatomical obstructions or in those who do not tolerate non-invasive therapies. Procedures aim to enlarge or stabilize the airway.

Complications of untreated obstructive sleep apnea

Chronic untreated OSA is associated with serious health consequences:

• Persistent fatigue and cognitive impairment

• Increased risk of motor vehicle and workplace accidents

• Hypertension and accelerated cardiovascular disease

• Coronary artery disease, heart failure, and stroke

• Cardiac arrhythmias and sudden cardiac death

• Poor glycemic control in diabetes

• Increased perioperative risk

• Worsening of mood and anxiety disorders

In children and adolescents, OSA may manifest as behavioral problems, attention deficits, and impaired academic performance.

Prevention and long-term management

While not all cases are preventable, risk reduction strategies include:

• Maintaining a healthy body weight

• Avoiding tobacco use

• Managing nasal obstruction

• Addressing contributing medical conditions

• Seeking evaluation for persistent snoring or excessive daytime sleepiness

Long-term follow-up is important, as obstructive sleep apnea is often a chronic condition requiring ongoing management.

Scientific references

1. Young T, Peppard PE, Gottlieb DJ. Epidemiology of obstructive sleep apnea: a population health perspective. American Journal of Respiratory and Critical Care Medicine. 2002;165(9):1217–1239.

2. Jordan AS, McSharry DG, Malhotra A. Adult obstructive sleep apnoea. The Lancet. 2014;383(9918):736–747.

3. Epstein LJ, Kristo D, Strollo PJ, et al. Clinical guideline for the evaluation, management and long-term care of obstructive sleep apnea in adults. Journal of Clinical Sleep Medicine. 2009;5(3):263–276.

4. Marin JM, Carrizo SJ, Vicente E, Agusti AGN. Long-term cardiovascular outcomes in men with obstructive sleep apnea. The Lancet. 2005;365(9464):1046–1053.

5. Punjabi NM. The epidemiology of adult obstructive sleep apnea. Proceedings of the American Thoracic Society. 2008;5(2):136–143.