Catathrenia

Catathrenia, or nocturnal groaning, is a sleep-related breathing disorder consisting of end-inspiratory apnea, meaning breath holding, and expiratory groaning during sleep, producing monotonous and irregular groans while a person sleeps. It begins with a deep inspiration, after which the person holds their breath against a closed glottis, similar to the Valsalva maneuver; expiration can be slow and accompanied by a sound from vocal cord vibration or a simple, rapid exhalation, and despite the slower breathing rate no oxygen desaturation usually occurs. The moaning sound is usually not noticed by the person producing it but can be extremely disturbing to sleep partners, and it appears more often during REM sleep than NREM sleep. Catathrenia is distinct from both somniloquy, or sleep talking, and obstructive sleep apnea, since the sound is produced during exhalation rather than inhalation as with snoring. It was initially classified as a parasomnia in the ICSD-2 and reclassified as a respiratory disorder in the ICSD-3.