Catathrenia

Catathrenia or nocturnal groaning is a sleep-related breathing disorder, consisting of end-inspiratory apnea (breath holding) and expiratory groaning during sleep. It describes a rare condition characterized by monotonous, irregular groans while sleeping. Catathrenia begins with a deep inspiration. The person with catathrenia holds his or her breath against a closed glottis, similar to the Valsalva maneuver. Expiration can be slow and accompanied by sound caused by vibration of the vocal cords or a simple rapid exhalation. Despite a slower breathing rate, no oxygen desaturation usually occurs. The moaning sound is usually not noticed by the person producing the sound, but it can be extremely disturbing to sleep partners. It appears more often during expiration REM sleep than in NREM sleep.

Catathrenia is distinct from both somniloquy (sleep talking) and obstructive sleep apnea (OSA). The sound is produced during exhalation, as opposed to snoring, which occurs during inhalation.