Sleep Medicine · OSA · Clinical Pearl
A normal overall AHI can hide clinically important REM-predominant OSA
Lede: Whole-night averaging can dilute a substantial REM-specific obstructive burden, especially when REM occupies only a limited fraction of total sleep time.
Why it matters
Upper-airway muscle tone falls during REM sleep, making the airway more vulnerable to collapse. REM events are often longer and more desaturating than NREM events, and observational data link REM-predominant OSA with hypertension and possible cardiometabolic risk. However, definitions vary and the clinical significance of REM-only disease—particularly when the overall AHI is below the conventional diagnostic threshold—remains an area of uncertainty.
The pearl
Always inspect the REM AHI, oxygen pattern, REM duration, and clinical context rather than relying on the whole-night AHI alone.
