Catathrenia is a sleep-related breathing disorder defined by the involuntary production of a groaning or moaning sound during sleep, often called nocturnal groaning. The person experiencing the sound is typically unaware it is happening, which often causes confusion for bed partners.
What Exactly is Catathrenia?
Catathrenia involves a distinct breathing pattern. The event begins with a deep inhalation, followed by a prolonged, strained exhalation that produces a monotonous vocalization. This groaning sound originates from the larynx (voice box) and results from a subtotal closure of the glottis during the expiratory phase.
The vocalization is highly variable, often lasting from a few seconds up to nearly 50 seconds. Although historically considered a parasomnia, catathrenia is currently classified as a sleep-related breathing disorder due to its physiological mechanism. Episodes occur most frequently during the Rapid Eye Movement (REM) stage of sleep, though they can also manifest during non-REM stages.
Understanding the Prevalence
Catathrenia is generally considered an uncommon disorder, and its true prevalence remains unestablished in the general population. Limited data comes primarily from specialized sleep centers, which introduces a selection bias for people already seeking treatment. This suggests the condition is significantly underreported.
Specific reports from sleep clinics indicate very low rates among those undergoing studies. For instance, an incidence of 0.17% was reported from a large series of over 15,000 patients at a Japanese sleep center. Similarly, a study in Norway noted an incidence of 0.4% among patients undergoing nocturnal polysomnography.
The difficulty in obtaining concrete statistics stems from the fact that catathrenia is frequently misdiagnosed or overlooked. It can be easily mistaken for simple snoring, sleep talking, or certain types of sleep apnea.
Distinguishing Catathrenia from Other Sleep Sounds
The primary distinction between catathrenia and common snoring lies in the respiratory phase during which the sound is produced. Snoring occurs during inhalation, as air causes soft tissues in the pharynx to vibrate. Conversely, catathrenia is an expiratory sound, meaning the groaning happens as the individual breathes out.
The source of the sound also differs; catathrenia originates in the larynx, while snoring comes from the throat. Catathrenia is separate from obstructive sleep apnea (OSA), which involves breathing pauses and often gasping or choking sounds upon inhalation. Individuals with catathrenia generally do not experience the significant drops in blood oxygen saturation that characterize severe OSA.
The protracted exhalation of catathrenia may sometimes resemble central sleep apnea (CSA) on a sleep study. However, the event is typically preceded by a deep inhalation, and the characteristic vocalization confirms it as nocturnal groaning, not a central respiratory effort issue. Unlike both types of apnea, catathrenia is not associated with serious health consequences, making it more of a social disturbance than a medical threat.
Diagnosis and Management
Confirmation of catathrenia requires a full nocturnal polysomnography (PSG), a specialized overnight sleep study. This comprehensive test measures brain waves, heart rate, breathing, and muscle activity, and includes audio recording to capture the specific nature of the sound. The PSG is necessary to differentiate the expiratory groaning from other sleep disorders.
Management strategies are primarily aimed at improving the sleep quality of the bed partner, as the affected individual is often asymptomatic. Continuous Positive Airway Pressure (CPAP) therapy is a common treatment, delivering pressurized air to help keep the airway open and reduce or eliminate the groaning events. Some patients may also find relief using a custom-fitted oral appliance that helps maintain an open upper airway.