Pathophysiology of sleep apnea.

Area of Science:

• Sleep Medicine
• Respiratory Physiology
• Neuroscience

Background:

• Sleep-induced apnea and disordered breathing, or obstructive sleep apnea (OSA), involves intermittent airflow reduction due to upper airway collapse.
• Reduced tonic input to upper airway dilator muscles during sleep contributes to pharyngeal airway collapse in compromised airways.

Observation:

• Neurochemical regulation of pharyngeal motor neurons and airway patency involves neurotransmitters and neuromodulators.
• Pharmacotherapies for sleep-induced airway obstruction have shown limited specificity.
• Long-term sequelae of severe OSA are studied via CPAP in humans and intermittent hypoxemia (IH) in animal models.

Findings:

• Cardiovascular: Strong evidence links severe OSA to daytime systemic hypertension, with less conclusive links to pulmonary hypertension, stroke, coronary artery disease, and arrhythmias. Mechanisms include enhanced chemoreceptor sensitivity, sympathetic overactivity, and inflammation.
• Metabolic: Intermittent hypoxemia and sleep disruption negatively impact insulin sensitivity and glucose regulation, but their independent contribution to the metabolic syndrome, apart from obesity, is debated.
• Neurocognitive: Hypoxic-induced neural injury results in daytime sleepiness, impaired memory, and concentration.

Implications:

• Understanding the pathophysiology of sleep apnea is crucial for developing novel treatments for both the breathing disorder and its associated health consequences.
• Future research should focus on uncovering new therapeutic strategies targeting the underlying mechanisms of OSA and its sequelae.
• Addressing OSA is critical for mitigating risks of cardiovascular disease, metabolic dysfunction, and neurocognitive impairment.