Respiratory Effort-Related Sleep Arousal (RERA)
Respiratory effort-related arousals (RERAs) are brief awakenings from sleep that happen after short periods of slowed breathing. Recurring RERAs during the night can cause fragmented sleep and daytime drowsiness.
RERAs are one type of breathing-related sleep disruption associated with obstructive sleep apnea (OSA). RERAs are generally diagnosed and treated in the same way as OSA.
What Is a Respiratory Effort-Related Arousal (RERA)?
A respiratory effort-related arousal (RERA) is a temporary awakening from sleep that occurs after 10 or more seconds of decreased nasal breathing.
When breathing slows, it can trigger a brief arousal so that normal breathing can be resumed. Even though sleepers usually do not remember these awakenings, the disruptions can throw off sleep cycles and worsen sleep.
RERAs can only be detected during an in-clinic sleep study that monitors breathing and brain activity. The sensors used in a sleep study can show RERAs, which involve a drop in airflow through the nose followed by a spike in brain activity caused by a partial awakening .
RERA vs. Other Sleep-Related Breathing Disruptions
RERAs are not the only type of sleep disruptions caused by irregular breathing. When testing for sleep apnea, RERAs are distinguished from apneas and hypopneas.
- Apneas: Apneas involve significant pauses in breathing. To be classified as an apnea, a person’s breathing must slow by 90% or more for at least 10 seconds.
- Hypopneas: Hypopneas are partial reductions in breathing. During a sleep study, hypopneas are identified when breathing slows by 30% or more for a period of at least 10 seconds, leading to a brief awakening or a 3% drop in blood oxygen levels.
- RERAs: Breathing reductions in RERAs are more mild than with apneas or hypopneas. RERAs involve 10 or more seconds of decreased nasal breathing immediately followed by an arousal from sleep.
While apneas, hypopneas, and RERAs all indicate a slowing of breathing during sleep, an important difference is that RERAs do not involve a drop in blood oxygen levels.
A person whose sleep disruptions are mostly RERAs may be described as having a subtype of OSA called upper airway resistance syndrome (UARS). Among people with OSA, those with UARS usually have more mild sleep fragmentation. They may also be less likely to have cardiovascular complications since they do not have repeated drops in their blood oxygen levels during sleep.
Causes of RERA
Like apneas and hypopneas, RERAs are caused when breathing is restricted by a narrowing of the upper airway. These sleep disruptions repeatedly occur during the night in people with OSA.
RERAs are more common in people with certain facial features that inhibit airflow through the nose. Some other factors that can increase the risk of OSA include nasal congestion, obesity, and being of an older age.
Symptoms of RERAs
When a person experiences multiple RERAs during the night, it can interfere with their sleep. Symptoms of recurring RERAs can include:
- Snoring that may involve snorting or choking
- Waking up unrefreshed
- Excessive fatigue or sleepiness during the day
- Difficulty concentrating or thinking
Other potential symptoms of obstructive sleep apnea, which frequently involves RERAs and other breathing disruptions, include:
- Dry mouth
- Morning headaches
- Having a hard time staying asleep through the night
- Frequent urination at night
Anyone with these symptoms should talk with a doctor to determine whether they may be caused by OSA.
Diagnosing RERA
The only way to dependably identify RERAs is to do an overnight sleep study in a sleep lab. During the study equipment tracks various bodily functions, including brain activity, sleep stages, and breathing. With this data, a sleep technician can detect apneas, hypopneas, and RERAs.
However, not all sleep studies include a count of RERAs. In some labs, only apneas and hypopneas are considered when diagnosing sleep apnea.
Many sleep labs report a metric called the respiratory distress index (RDI), which is the combined total of apneas, hypopneas, and RERAs divided by the time a person spent sleeping. The apnea-hypopnea index (AHI) is a similar calculation that does not include RERAs. Both the AHI and RDI can be used to assess the severity of sleep apnea, but there is no consensus among experts about which metric is most useful.
Although home sleep apnea tests can diagnose OSA in some people, these tests cannot measure RERAs because they do not monitor brain activity. Positive airway pressure (PAP) devices, like CPAPs, also cannot measure RERAs.
“Having RERAs are only something one would know from a sleep study. What’s most important is speaking to your doctor if you have any symptoms that could indicate OSA, like loud snoring/gasping, excessive daytime sleepiness, dry mouth or morning headaches.”
Dr. Dustin Cotliar, Sleep Physician
Treatment for RERA
Isolated or infrequent RERAs may not require treatment. However, treatment may be needed when RERAs occur as part of OSA and when they cause significant sleep disruptions.
For people with OSA, the goal of treatment is to eliminate as many apneas, hypopneas, and RERAs as possible. One of the most common treatments involves using a continuous PAP (CPAP) or auto-adjusting PAP (APAP) device during sleep. These devices send pressurized air into the upper airway to prevent breathing from being restricted.
Other approaches to treating OSA and RERAs may include:
- Wearing a custom-fitted oral appliance during sleep
- Making behavioral changes like losing weight, changing sleep position, and avoiding alcohol before bed
- Having surgery to implant a device to stimulate nerves that affect muscles around the airway
- Having surgery to remove or modify tissue that can block the airway
Not all of these treatments are viable options for everyone with OSA or RERAs. It is important to consult with a doctor about the most appropriate treatment in any specific person’s situation.
Eric Suni has over a decade of experience as a science writer and was previously an information specialist for the National Cancer Institute.
Dustin Cotliar holds a medical degree from the State University of NY (SUNY) Downstate College of Medicine, and a master’s in public health from Columbia University, where he focused on healthcare policy and management. He is board-certified in Emergency Medicine, with over eight years of practice that includes emergency medicine, urgent care, and telemedicine.
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