Obstructive Sleep Apnea in Adults
Pathophysiology and diagnosis
OSA results from recurrent upper airway collapse during sleep, driven by anatomic narrowing, reduced pharyngeal muscle tone, and impaired arousal. Risk factors include obesity, male sex, age, craniofacial features, and menopause. Symptoms are snoring, witnessed apneas, unrefreshing sleep, and daytime sleepiness. Diagnosis requires AHI of 5 or more with symptoms, or AHI of 15 or more regardless of symptoms.
Severity and consequences
Mild is AHI 5-15, moderate 15-30, severe above 30. Untreated OSA associates with hypertension, atrial fibrillation, stroke, and metabolic dysfunction. The Epworth Sleepiness Scale quantifies subjective sleepiness but does not diagnose OSA.
Treatment
Positive airway pressure is first-line for moderate-severe disease. Alternatives include mandibular advancement devices for mild-moderate OSA or CPAP intolerance, positional therapy, weight loss, and surgery. Adherence to PAP is defined by usage of 4 or more hours per night on 70% of nights.
Traps
- AHI vs ODI: oxygen desaturation index may differ; do not equate them.
- Central events on PAP (treatment-emergent central apnea) can appear after obstructive events resolve.
- Normal BMI does not exclude OSA; craniofacial anatomy matters.
Rule of thumb
Match severity to therapy: mild with positional component may respond to positional therapy; moderate-severe warrants PAP first.