Central Sleep Apnea | Why Does the Brain Forget to Breathe During Sleep?

Central Sleep Apnea (CSA) is a neurological sleep disorder where breathing repeatedly stops and starts during sleep. Unlike the more common Obstructive Sleep Apnea (OSA), CSA is not caused by a physical blockage of the airway. Instead, it originates in the central nervous system. Specifically, the brainstem, which houses the respiratory control center, fails to send the necessary signals to the muscles that control breathing. During a CSA episode, there is no respiratory effort because the command to breathe is absent. This control system relies on specialized neurons that monitor carbon dioxide (CO2) levels in the blood. When CO2 levels rise, these neurons are supposed to trigger an inhalation. In individuals with CSA, this feedback loop is unstable or impaired. The brain becomes less sensitive to rising CO2 levels or, in some cases, overreacts to changes, leading to a cyclical pattern of paused breathing (apnea) followed by compensatory rapid breathing (hyperpnea). This instability disrupts the normal, automatic rhythm of respiration that should be maintained even during unconsciousness, profoundly affecting sleep architecture and overall health.

The fundamental distinction between Central Sleep Apnea (CSA) and Obstructive Sleep Apnea (OSA) lies in the presence or absence of respiratory effort. In OSA, the brain correctly sends the signal to breathe, but the airway is physically obstructed, typically by the collapse of soft tissues in the throat. This leads to strained breathing efforts, often characterized by loud snoring, gasping, or choking sounds, as the person struggles against the blockage. In contrast, CSA is a problem of communication; the brain itself does not initiate the effort to breathe. Consequently, during a central apnea event, all respiratory movements cease—the chest and abdomen do not move. Snoring is much less common in pure CSA. While both conditions result in drops in blood oxygen levels and fragmented sleep, the underlying cause dictates the diagnosis and treatment. Put simply, OSA is a mechanical problem of "can't breathe," whereas CSA is a neurological problem of "won't breathe."

Central Sleep Apnea is most often a secondary condition, meaning it is caused by another medical issue. The most prevalent cause is advanced heart failure, which leads to a specific pattern called Cheyne-Stokes respiration, characterized by cyclical episodes of deep, rapid breathing followed by apnea. Neurological conditions that damage the brainstem, such as stroke, brain tumors, or infections, can directly impair the respiratory control centers. Additionally, the use of opioid medications is a significant and increasingly common cause, as these drugs suppress the central nervous system's respiratory drive. Less frequently, CSA can be idiopathic (having no known cause) or can occur in healthy individuals at high altitudes, where lower oxygen levels can destabilize the breathing pattern during sleep.

The symptoms of CSA can be subtle and may overlap with other sleep disorders, but key differences exist. While OSA is famous for loud, disruptive snoring, individuals with CSA are often quiet during their apneic pauses. The most telling sign, often reported by a bed partner, is the complete cessation of breathing movements. Sufferers themselves may experience abrupt awakenings accompanied by a sensation of shortness of breath, insomnia due to repeated arousals, or significant daytime sleepiness. Morning headaches, difficulty concentrating, and mood changes are also common due to poor sleep quality and fluctuating oxygen levels. Unlike the choking or gasping associated with OSA, the awakening from a central apnea can feel more like a sudden, unexplained arousal from sleep.

The definitive diagnosis of Central Sleep Apnea is made through an overnight sleep study known as polysomnography (PSG). This comprehensive test monitors various physiological parameters, including brain waves (EEG), eye movements, muscle activity, heart rhythm, and, most importantly, respiratory effort and airflow. The PSG can clearly distinguish between central and obstructive apneas by demonstrating a lack of respiratory effort during the breathing pause. Treatment for CSA primarily focuses on addressing the underlying medical condition, such as optimizing heart failure management or reducing opioid dosage under medical supervision. For direct treatment of the breathing issue, options include various forms of positive airway pressure (PAP) therapy. While CPAP (Continuous Positive Airway Pressure) is the standard for OSA, a more advanced therapy called Adaptive Servo-Ventilation (ASV) is often more effective for CSA. ASV is an intelligent device that adjusts its pressure support on a breath-by-breath basis to stabilize the breathing pattern and eliminate apneic events.