Catathrenia groans may only last a couple of seconds in duration or go on for nearly a minute (via Sleep Foundation). Affecting both kids and adults, the cause of the condition is not entirely known. Those who have a family member with this particular sleep issue may be more susceptible to the condition. Abnormal neural activity in the brain region associated with breathing is another theory. People living with catathrenia also tend to share certain physical characteristics, such as a small jaw, smaller upper airways, and limitations in airflow.
Researchers from a 2011 case report published in the European Respiratory Journal conducted a laryngoscopy on a woman in her late 20s experiencing nighttime groaning and other occasional sleep issues. Study findings showed that while inhaling, the woman’s glottis stayed open. Critical for both breathing and voice production, the glottis acts as a valve situated between the mouth and the lungs that expands, contracts, and vibrates (via ScienceDirect). When the woman exhaled, however, the glottis closed almost entirely, prompting a groaning sound.