Central sleep apnea (CSA) is a sleep disorder where breathing repeatedly stops and starts during sleep. This occurs because the brain temporarily fails to send the necessary signals to the muscles that control breathing.
Understanding How Central Sleep Apnea Occurs
Normal breathing during sleep is a process controlled by the brain’s respiratory center. This center, located in the brainstem, sends electrical signals through nerves to the diaphragm and other breathing muscles, prompting them to breathe.
In central sleep apnea, the issue is with this command center. Unlike obstructive sleep apnea (OSA), where a physical blockage prevents air from reaching lungs despite breathing effort, CSA involves a lack of effort to breathe. The brain does not send the signal to inhale, causing temporary pauses. Pauses can last 10 to 30 seconds and reduce blood oxygen levels.
The brain’s respiratory drive is dependent on carbon dioxide levels. When carbon dioxide levels rise, the brainstem signals the respiratory muscles to breathe more. In CSA, this feedback mechanism can become unstable, causing periods of both reduced and increased breathing that cycle.
Medical Conditions That Lead to Central Sleep Apnea
Several medical conditions can directly impact the brain’s ability to regulate breathing during sleep, leading to central sleep apnea.
One cause is severe heart failure, resulting in Cheyne-Stokes breathing. In this pattern, breathing effort and airflow gradually increase and decrease, sometimes stopping entirely before the cycle repeats. This cyclical breathing is common in congestive heart failure, reflecting the body’s unstable response to oxygen and carbon dioxide changes.
Impaired kidney function, including end-stage renal disease, can contribute to CSA. When kidneys fail, they are unable to filter waste products, disrupting chemical balance. This imbalance can affect the brain’s control over breathing, leading to irregular respiratory patterns during sleep.
Neurological disorders affecting the brainstem or cerebellum are also causes. These regions are important for respiratory control. Conditions like stroke, brain tumors, or degenerative diseases (e.g., Parkinson’s) can damage these areas, interfering with consistent breathing signals. Damage to these pathways impacts respiration rhythm and depth, especially during sleep when voluntary control is absent.
Thyroid disorders, like hypothyroidism, can contribute to central sleep apnea. An underactive thyroid can slow metabolic processes influencing respiratory drive. This slows respiratory effort during sleep, leading to periods of central apnea.
Medications and Environmental Factors
External influences, including certain medications and environmental conditions, can also induce or worsen central sleep apnea.
Opioid medications are a common cause of central sleep apnea. These pain relievers depress the central nervous system, including the brain’s respiratory drive. Opioids can reduce the brain’s sensitivity to carbon dioxide, leading to reduced breathing effort and sleep pauses. The effect can be seen with opioid use.
Ascending to high altitudes is another environmental factor. Less oxygen at high altitudes changes the body’s oxygen and carbon dioxide balance. The body compensates by breathing faster, but this can lead to too much carbon dioxide exhaled. This low carbon dioxide then suppresses the brain’s signal to breathe, causing central apneas. This is seen as periodic breathing.
Other medications that depress the central nervous system, like sedatives or tranquilizers, can also contribute to CSA. These substances can reduce the brain’s responsiveness to breathing cues. Certain cardiac medications may also affect respiratory regulation, contributing to CSA.
Central Sleep Apnea Without a Clear Cause
Sometimes, central sleep apnea occurs without any identifiable medical condition, medication, or environmental trigger. This form is often referred to as idiopathic or primary central sleep apnea. The brain’s respiratory control does not function correctly during sleep for unknown reasons.
When no specific cause is found after evaluation, the diagnosis of primary central sleep apnea is made by exclusion. This means that doctors have ruled out known contributing factors. Despite extensive research, the mechanisms behind this type of CSA remain an area of ongoing study, highlighting the complexity of the brain’s role in regulating breathing during sleep.