A 45-year-old obese male reports loud snoring, witnessed apnoeic episodes, and non-restorative sleep with excessive daytime somnolence. He scores 16 on the Epworth Sleepiness Scale. Overnight polysomnography shows Apnoea-Hypopnoea Index (AHI) = 32 events/hour. The investigation of choice to confirm and quantify this disorder has been performed. What is the AHI threshold for SEVERE Obstructive Sleep Apnoea?

• A >5 events/hour
• B >30 events/hour ✓
• C >15 events/hour
• D >50 events/hour

Explanation

Obstructive Sleep Apnoea (OSA) severity is graded by AHI: Mild OSA: 5–15 events/hour; Moderate OSA: 15–30 events/hour; Severe OSA: >30 events/hour. This patient's AHI of 32 represents severe OSA, requiring immediate CPAP therapy. The Epworth Sleepiness Scale >10 is clinically significant; >16 indicates severe daytime somnolence. Gold-standard diagnosis is overnight in-lab polysomnography; portable home sleep apnoea testing (HSAT) is an acceptable alternative for moderate-severe uncomplicated suspected OSA. CPAP therapy reduces cardiovascular mortality, improves neurocognitive function, and reduces accident risk.

Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.

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Written and medically reviewed by the StethoPrep medical team.