Making loud, strange noises while sleeping can be confusing, especially when the sleeper is unaware of the sound. This phenomenon is a sleep-related breathing disorder known as nocturnal groaning, or catathrenia. The sound is not a sign of distress or a nightmare, but rather an involuntary vocalization tied to a distinctive breathing pattern during sleep. Understanding catathrenia brings clarity to this common, yet often misunderstood, nightly occurrence.
Identifying Sleep-Related Expiratory Groaning
Catathrenia is defined by a specific sound: a long, drawn-out moan, hum, or grunt produced during exhalation. The sound is typically monotonous and can be quite loud, meaning a bed partner is often the first to notice the condition. It is a chronic disorder that usually begins in childhood or early adulthood.
The groaning episodes can last from a few seconds to almost a full minute and may occur in clusters throughout the night. This vocalization is distinct from sleep talking because the sounds are not related to language or dream content. Catathrenia is classified as a sleep-related breathing disorder due to the unusual breathing pattern and involuntary respiratory effort that accompanies the noise.
The Physiological Mechanism Behind the Groaning
The groaning sound is a byproduct of an altered breathing pattern involving the larynx, or voice box. The sequence begins with an unusually deep inhalation, followed by breath-holding against a closed glottis, the opening between the vocal cords. This action is similar to the Valsalva maneuver, which involves forced exhalation against a closed airway.
The air is then slowly released during a prolonged expiration through the partially closed larynx. This restricted airflow causes the vocal cords to vibrate, generating the characteristic groaning noise. This physiological action is often called laryngeal braking, where the airway is intentionally constricted to slow the release of air.
The respiratory pattern during an episode is characterized by slowed breathing, known as bradypnea. While catathrenia can occur in any sleep stage, it is seen more frequently during Rapid Eye Movement (REM) sleep. Researchers hypothesize the cause may involve a malfunction in the brain’s respiratory control center, which dictates the timing and duration of breaths.
How Catathrenia Differs from Snoring and Sleep Apnea
The difference between catathrenia and other common sleep noises lies in the timing of the sound. Snoring occurs during inhalation when air causes the soft tissues of the throat to vibrate. In contrast, catathrenia is exclusively an exhalation phenomenon that originates lower in the airway at the larynx.
A more significant distinction exists between catathrenia and Obstructive Sleep Apnea (OSA). OSA involves repeated episodes of upper airway collapse, leading to temporary cessation of breathing and subsequent drops in blood oxygen levels. People with OSA often experience excessive daytime fatigue resulting from fragmented sleep and oxygen deprivation.
Catathrenia is generally considered a benign condition that does not typically result in oxygen desaturation or significant health risks. While breathing is slowed during groaning episodes, the airway remains open enough to prevent the dangerous oxygen drops associated with OSA. Unlike sleep apnea, catathrenia is rarely the cause of daytime sleepiness or other serious health issues for the sleeper.
When to Seek Diagnosis and Management Options
For many individuals, catathrenia does not require treatment, especially if they live alone and are not bothered by it. However, a consultation with a sleep specialist is recommended if the groaning severely disrupts a bed partner’s sleep or if the sleeper experiences associated symptoms like a persistent sore throat or unexplained daytime grogginess. The sound can also sometimes mask or occur alongside other sleep disorders, making an evaluation important.
Diagnosis is confirmed through an overnight sleep study, called polysomnography, which monitors brain activity, breathing patterns, and vocalizations. This test helps reliably differentiate catathrenia from other conditions, such as central sleep apnea or somniloquy. The most common and effective management strategy is the use of a Continuous Positive Airway Pressure (CPAP) machine.
The CPAP device gently delivers pressurized air through a mask, which helps stabilize the airway and minimize the groaning sounds. Other management options include oral appliances, which reposition the jaw to keep the upper airway open. In rare cases, surgical evaluation may be considered, but the main goal of management is typically to ensure restorative sleep for the bed partner.