What is Central Sleep Apnea?
Central sleep apnea (CSA) is a type of sleep disorder that involves temporary decrease or stopping of breath due to the occurrence of issues in the part of the brain that controls breathing. With CSA, there’s a brief lack of air exchange (breathing) during sleep, making it part of a group of sleep-related breathing conditions. People with CSA experience cycles of breathlessness or shallow breathing (apnea or hypopnea), alternated with deep, rapid breathing (hyperpnea) during sleep. Despite no apparent effort made to breathe during these periods, it’s observed that the throat passage constricts or almost closes up. This narrowing often happens at the back of the throat during CSA.
Even though CSA is less common compared to obstructive sleep apnea (OSA), a person can have features of both conditions. The International Classification of Sleep Disorders – Third Edition has listed several types of CSA, each with its unique clinical features and sleep test results. These categories are Primary CSA, CSA with Cheyne-Stokes Breathing (CSB), CSA due to a medical disorder without CSB, CSA because of periodic high-altitude breathing, CSA because of a medication or substance, and Treatment-emergent CSA.
Both low and excessive breathing can lead to CSA, each through a different biological mechanism. Thus, the level of breathing can often serve as an alternative way to categorize CSA. For instance, patients with heart failure often have low carbon dioxide levels during wakefulness which can lead to CSA associated with over-breathing. Contrastingly, CSA related to under-breathing is common in conditions like a neuromuscular disease (like amyotrophic lateral sclerosis and brainstem stroke), certain medication use (like opioids) with central nervous system side effects, cervical spinal cord injury, or with physical abnormalities that affect lung function, like kyphoscoliosis.
What Causes Central Sleep Apnea?
People suffering from various health issues can experience changes in their breathing during sleep, leading to a condition called central sleep apnea (CSA). Conditions like heart rhythm disorders (atrial fibrillation), heart failure (whether with preserved or reduced heart pumping power), stroke, spinal cord injuries, kidney failure and long-term use of opioids can make someone more likely to develop CSA due to changes in their breathing.
CSA is particularly common in individuals with heart-related conditions, and can even be a standalone risk factor that leads to poor health outcomes. In some rare cases, there are no clear causes of CSA, and these cases are known as idiopathic or primary.
Risk Factors and Frequency for Central Sleep Apnea
Research by Bixler and his team showed that older adults are more likely to suffer from central sleep apnea compared to middle-aged people (12.1% vs. 1.8%). It’s noteworthy that the likelihood of having central sleep apnea increases as people age, particularly in those over the age of 65. A specific study found that 2.7% of men aged 65 and older have central sleep apnea, according to a widely used classification system.
- Older adults are more likely to have central sleep apnea than middle-aged people based on a study by Bixler’s team.
- The likelihood of having central sleep apnea goes up with age, especially among those over 65 years old.
- A study found 2.7% of men aged 65 and above to have central sleep apnea.
One explanation for this trend is that older people are more chemically responsive, which makes them prone to central sleep apnea, particularly during non-rapid eye movement sleep. Women, in comparison to men, are less susceptible and typically need a higher level of hypocapnia (abnormally low levels of carbon dioxide in the blood) to develop central sleep apnea.
Signs and Symptoms of Central Sleep Apnea
Central sleep apnea (CSA) causes individuals to often experience poor sleep quality, frequent waking up during the night, broken sleep patterns, excessive sleepiness during the day, headaches in the morning, fatigue, and difficulties concentrating. On the other hand, snoring isn’t usually a major symptom with CSA, unlike other forms of sleep apnea. Although Obstructive sleep apnea (OSA) and CSA are separate health conditions, there are situations where a patient might experience symptoms of both. OSA is commonly related to higher body weight, whereas individuals with CSA are generally less overweight.
Extra symptoms can surface in CSA patients due to underlying health conditions, particularly in those with hypercapnic central apnea, which involves high levels of carbon dioxide in the body. Interestingly, people with heart failure often don’t report or notice symptoms during the daytime, even when testing shows they are excessively sleepy. This phenomenon could be because the body’s “fight or flight” system is more active during the day, increasing alertness and offsetting the feeling of sleepiness.
In a recent study, researchers found that the less sleepy a person feels during the day, the higher their risk of mortality. Hence, doctors should consider sleep apnea as a possible diagnosis in older heart failure patients who report fatigue, even if they don’t exhibit the standard excessive daytime sleepiness.
Testing for Central Sleep Apnea
Diagnosing Central Sleep Apnea (CSA) is not always straightforward based solely on patient reports of poor sleep. The best way to confirm CSA is through a diagnostic test called nocturnal polysomnography (PSG). These standards for diagnosing CSA have been provided by the American Academy of Sleep Medicine, and it can differ depending on the specific kind of CSA. Diagnosis typically involves recurrent patterns of central apnea, which is when there is a pause in breathing lasting at least 10 seconds during sleep without any effort made to breathe.
If the PSG test shows that there are 5 or more central apneas and/or central hypopneas (shallow breaths) for every hour of sleep, and these central events make up more than half of all breathing events during sleep, then a primary CSA diagnosis can be made. This is as long as there is no evidence of a type of breathing called Cheyne-Stokes breathing (CSB). In addition, the patient must also report at least one symptom related to disrupted sleep, like sleepiness, insomnia, waking up short of breath, snoring, or instances of stopped breathing that have been observed.
The criteria for diagnosing CSA with CSB are the same as those for primary CSA, but the patient must also have three or more consecutive central apneas or hypopneas that are spaced out between cycles of increased and decreased breathing that each last for at least 40 seconds.
To diagnose what’s known as treatment-emergent central apnea, there must first be a primary diagnosis of Obstructive Sleep Apnea (OSA) that shows an apnea-hypopnea index of 5 or more obstructive respiratory events per sleep hour. Following the resolution of the OSA, if central apnea still persists or appears during a treatment method known as positive airway pressure therapy study, and isn’t caused by any other condition or substance, then this type of CSA can be diagnosed.
Treatment Options for Central Sleep Apnea
The main aim in treating central sleep apnea (CSA) is to stabilize sleep and manage related health conditions. Various devices and treatments are available, such as Positive Airway Pressure (PAP) which helps to prevent breathing interruptions. There are several types of PAP, including continuous PAP (CPAP) and Bi-level PAP (BPAP). Other potential treatments include oxygen supplements, carbon dioxide, and medication.
Since CSA can vary greatly from patient to patient, it requires personalized treatment plans. These could include mechanical devices, such as CPAP, oxygen treatment, nerve stimulators, or medication.
Looking at mechanical devices:
– CPAP, which stops the airway from closing when you’re asleep, is often the first treatment suggested. Many research studies have shown it to be beneficial. While it doesn’t significantly reduce the risk of death, it can notably decrease the number of breathing interruptions during sleep in patients with CSA and heart failure (HF).
– BPAP can be useful, particularly if the patient doesn’t respond to CPAP. This treatment improves ventilation and air volume in the lungs. It’s been found to be helpful in patients with HF and CSA.
– Adaptive servo-ventilation (ASV) is another type of PAP that adjusts to the patient’s breathing effort and provides controlled pressure. It can be good for patients who have a preserved ejection fraction (EF), which is a measure of how well the left ventricle of the heart pumps blood with each beat. However, a large study showed that it increased mortality in HF patients with a reduced EF so it’s not advised for these people.
Other treatment options include:
– Night-time oxygen therapy, which has been shown to reduce apnea episodes and improve quality of life and the heart’s ability to pump blood.
– Placement of phrenic nerve stimulators, a treatment that helps control the diaphragm’s movements, has been associated with improved CSA severity and quality of life, regardless of the patient’s HF status.
– Various medications have been thought to potentially help manage CSA, such as sleeping pills which can increase overall sleep time while reducing the central apnea index, or respiratory stimulants that increase the need to breathe and lower the frequency of central apneas. But there’s currently no approved drug treatment for CSA. Other possible medicines need to be extensively studied and tested before they can be officially used for treatment.
What else can Central Sleep Apnea be?
There are several health issues that can cause symptoms similar to central sleep apnea. Doctors need to investigate these conditions before confirming a diagnosis of central sleep apnea. Some of these conditions may cause excessive sleepiness during the day or other symptoms that could interfere with a good night’s sleep. The conditions to consider include:
- Obstructive sleep apnea (a disorder where your breathing stops and starts while you sleep)
- Periodic limb movements of sleep (a disorder that causes your limbs to move involuntarily while you’re sleeping)
- Narcolepsy (a chronic sleep disorder characterized by overwhelming daytime drowsiness and sudden attacks of sleep)
- Obstructive and restrictive lung diseases (conditions that make it hard to breathe)
- Neuromuscular diseases (conditions that affect the nerves controlling your muscles)
- People who work night shifts or have inconsistent sleep schedules
Therefore, it is crucial for a doctor to carefully consider these possibilities and carry out tests in order to make an accurate diagnosis.
What to expect with Central Sleep Apnea
Patients with heart failure who also experience certain types of sleep problems tend to have a poorer outlook, and their treatment often involves better management of their heart failure.
Adaptive servo-ventilation (ASV) is a treatment that uses a machine to physically assist your breathing, applying different amounts of pressure during inhalation and exhalation. However, a 2015 study found that patients with a reduced measure of how much blood the heart is pumping out (known as the ejection fraction, or EF) that were treated with ASV reportedly experienced increased rates of death from any cause and heart problems without significant improvement in their symptoms or quality of life. Therefore, the usage of ASV in heart failure patients with reduced EF has been associated with higher death rates.
Possible Complications When Diagnosed with Central Sleep Apnea
People who have sleep apnea syndrome often have a higher chance of experiencing several health issues. These could include:
- Systemic hypertension (high blood pressure throughout the body)
- Pulmonary hypertension (high blood pressure in the lungs)
- Arrhythmias including atrial fibrillation (irregular heartbeat issues)
- Sleep disturbances that result in excessive sleepiness during the day
- Mood disorders
- Chronic respiratory failure (long-term inability of the respiratory system to function properly)
- Narcolepsy (a neurological disorder causing excessive daytime sleepiness)
- Hypercapnic respiratory failure (respiratory failure due to high levels of carbon dioxide in the blood)
Preventing Central Sleep Apnea
Patients and their families need to understand how sleep apnea works. Usually, when we sleep, air flows in and out of our lungs at a normal pace. However, for people with a type of sleep apnea known as central sleep apnea, there can be brief pauses in breathing. This happens because the controls for their breathing rhythm alter. This condition can affect their long-term health and quality of life, leading to symptoms like restless sleep, fatigue, trouble focusing, memory issues, and waking up still feeling tired.
The most reliable way to diagnose sleep apnea is with a sleep study named polysomnogram. This test measures the person’s breathing effort and airflow, vital signs, and the level of oxygen in their blood during different sleep stages. The treatment process includes identifying and dealing with any underlying causes. Ideally, patients should be reviewed by a doctor who specializes in sleep disorders.