What is Upper Airway Resistance Syndrome?
Sleep-disordered breathing disorders (SDB) include chronic conditions like snoring, upper airway resistance syndrome (UARS), obstructive sleep apnea (OSA), and central sleep apnea (CSA) along with its sub-types. All these conditions involve abnormal breathing patterns during sleep and the ways they are identified have evolved over time depending on the medical knowledge and technologies available.
UARS is a condition which has been studied for a long time, but researchers are still trying to agree on how it should be diagnosed and whether it’s a unique condition separate from OSA.
OSA and CSA are defined by the number of episodes of paused breathing (apnea) and shallow breathing (hypopnea) that happen per hour of sleep, known as the apnea-hypopnea index (AHI). On the other hand, UARS is generally defined as limited airflow due to increased efforts to breathe, which lead to wakefulness from sleep but without significant lack of oxygen in the body (desaturation). It is also associated with symptoms during the day. In more specific terms, UARS has been defined as AHI less than 5 events per hour, oxygen saturation more than or equal to 92%, and waking due to breathing efforts more than or equal to 5 times per hour. Another study defined UARS slightly differently, focusing on minimum oxygen levels, the presence of airflow limitation during sleep for at least 5% of total sleep time, and daytime sleepiness or fatigue.
This article will review the causes, prevalence, medical history and examination findings, evaluation, treatment, differential diagnosis (distinguishing between similar conditions), and complications of UARS. Information about OSA and CSA will be discussed in separate articles.
What Causes Upper Airway Resistance Syndrome?
There are several reasons why your upper airway – the part of your throat behind your nose and mouth – can narrow while you sleep. Some people have physical characteristics that make this more likely. For others, it’s because the brain and muscles aren’t working together as they should to keep the airway open. If the upper airway becomes partly narrowed, you can develop a condition known as Upper Airway Resistance Syndrome (UARS).
This condition typically happens between the hard roof of your mouth and the hanging bit at the back (the uvula), and between the uvula and the flap that covers your windpipe when you swallow (the epiglottis). The narrowing makes it more difficult to breathe in and can cause you to wake up frequently during the night, disrupting your sleep. This can make you feel tired during the day, even if you think you’ve had enough sleep. A key sign of UARS is having difficulty breathing during sleep without significant drop in oxygen levels in the blood and not necessarily meeting the definition of hypopnea, which refers to shallow or slow breathing.
UARS might be an early stage of Obstructive Sleep Apnea (OSA), a common sleep disorder that involves temporary stops in breathing during sleep. However, it’s hard to say for sure because there’s not enough research on this subject. If you have UARS, you can develop a narrowed airway during sleep over time, especially if you already have physical characteristics that make this more likely. This can cause you to wake up often during the night, leading to fragmented sleep scattered with periods of breathing trouble.
The narrowing of your airway can happen when you breathe in, breathe out, or both. This can be caused by the airway being more prone to collapse. The likelihood of this happening can be measured by using negative pressure on the airway until a critical closing pressure (Pcrit) is reached. In healthy people, this pressure is usually negative, but it can reach the positive range in people with UARS and other sleep-related breathing disorders.
How air flows and the resistance it meets in the upper airway can be explained by a principle known as Poiseuille’s law or the ‘Starling resistor’ model. This law states that the resistance in a tube (in this case, your airway) is inversely related to its diameter, meaning the smaller the airway, the greater the resistance. It also states that this resistance is directly related to the difference between the pressure at the start of the tube and Pcrit. If the pressure at the start approaches the Pcrit, the airway narrows and the airflow decreases until it stops entirely, such as in sleep apnea. In UARS, both breathing in and out can be limited because of the difference in pressure. Other chronic lung conditions like asthma and Chronic Obstructive Pulmonary Disease (COPD) can also cause snoring and trouble breathing out. One study even found that snoring while breathing out alone predicted lower airflow obstruction, also known as obstructive lung disease.
Risk Factors and Frequency for Upper Airway Resistance Syndrome
Upper airway resistance syndrome (UARS) is a condition that affects a small proportion of the population. Specific criteria are used to define UARS, including having less than five periods of paused breathing per hour during sleep, maintaining at least 92% blood oxygen levels, experiencing restricted breathing for 5% or more of sleep time, and enduring daytime tiredness or fatigue. In a recent study, about 3.1% of people had UARS, with women being more affected than men (4.4% versus 1.5%).
On the other hand, mild Obstructive Sleep Apnea (OSA), characterized by more than five periods of paused breathing per hour during sleep, is much more common. About 24% of men and 9% of women have this condition globally, affecting roughly one billion people.
- Although we don’t know exactly how many people have UARS, we know that it accounts for about 5.3% of all breathing issues during sleep among those with OSA.
- UARS is more common in women who are around the age of menopause, compared to men or women after menopause.
- Interestingly, women with UARS reported needing more sleep (around 30 minutes extra) compared to men with the same condition.
Signs and Symptoms of Upper Airway Resistance Syndrome
Upper airway resistance syndrome is a sleep disorder where patients typically report symptoms such as snoring, feeling tired during the day, headaches in the morning, feelings of depression, and excessive sleepiness throughout the day, though they don’t usually experience noticeable lapses in breathing or gasping during sleep. They may also experience frequent interruptions to their sleep and find themselves waking up unexpectedly, particularly after going to sleep for about 2 or 3 hours. These sudden wake-ups often accompany an increase in respiratory effort, which results in fragmented sleep and leads to fatigue and excessive sleepiness during the day. Notably, studies show that individuals who have upper airway resistance syndrome as well as Obstructive Sleep Apnea experience a quality of life that is significantly lower – about 5 to 6 times worse – as compared to the average person.
Testing for Upper Airway Resistance Syndrome
If doctors suspect that a person might have a condition called Upper Airway Resistance Syndrome (UARS), they usually recommend a full sleep study called polysomnography (PSG). Home sleep tests might not catch every detail of the sleep-disordered breathing (SDB) that’s a key part of UARS, while a full PSG can. This is because the PSG looks for both limited breath flow and wakeful moments that interrupt sleep, both needed to confirm a UARS diagnosis.
When compared with Obstructive Sleep Apnea (OSA), another sleep disorder, people with UARS tend to have more slow-wave sleep and wake up less during their sleep studies. In addition, while people with UARS might have moments where they stop breathing (apneas) or have shallow breathing (hypopneas) during sleep, these periods are usually less frequent. However, they tend to have episodes where their breath doesn’t flow easily, which leads them to wake up. These episodes are commonly known as respiratory effort-related arousals or RERAs.
UARS often goes unnoticed because these RERAs can be underestimated when doctors are going over the results of the PSG sleep study. As a result, the PSG study might wrongly be reported as normal or as indicating mild OSA instead of UARS. The condition can also be identified by measuring the pressure in the esophagus or with the help of a special instrument placed above the vocal cords, but these methods aren’t commonly used in most labs.
If left untreated, UARS can lead to a poor quality of life and even potentially serious heart issues over a period of time. The symptoms usually get worse in individuals with untreated UARS. If UARS isn’t managed, it could cause high blood pressure, heart-related issues, and metabolic disorders. Therefore, it is essential to identify and treat UARS as early as possible to avoid these complications.
Treatment Options for Upper Airway Resistance Syndrome
Upper Airway Resistance Syndrome (UARS) is a sleep disorder that can be treated in several ways. The treatments mainly focus on resolving issues that cause problems in the upper airway. Such problems can include nasal allergies, abnormal dental alignment, or unhealthy lifestyle habits.
One of the most common treatments for UARS is a therapy called Continuous Positive Airway Pressure (CPAP). This treatment involves using a machine to provide a steady stream of pressurized air to keep the upper airway open during sleep. Studies have shown that CPAP can reduce issues with breathing and heart rate during sleep, and make patients feel better. However, it’s important to ensure that the CPAP machine is calibrated correctly, which is often done in a sleep lab.
Oral appliances are another useful treatment option, especially for those who can’t tolerate CPAP or don’t want to have surgery. These appliances work by moving the lower jaw and surrounding soft tissues forward, which opens up more space behind the tongue. This can help ease stress symptoms of UARS. There are different types of oral appliances like devices that hold the tongue in place, lift the soft palate, or restrain the tongue.
Surgery becomes a consideration if a patient is not able to tolerate other therapies like CPAP or oral appliances. There are various surgical procedures that can be used to treat UARS, including surgeries involving the soft palate at the back of the mouth.
There is also interest in using medications as another form of treatment, but so far no drugs have been officially approved for this use. Some drugs called hypnotics that can help with sleep have been studied, showing mixed results. For example, there are studies on a drug called zolpidem where some showed it can help decrease sleep-related breathing problems, but others didn’t show any effect. So for now, drug treatment is deemed experimental and may possibly be used in conjunction with other treatments.
What else can Upper Airway Resistance Syndrome be?
Upper airway resistance syndrome is a condition that can appear similar to various other ailments. Conditions that might be confused with it include sleep disorders where breathing gets interrupted, such as:
- Obstructive sleep apnea syndrome
- Sleep-related breathing disorder
- Respiratory sleep disorder
- Sleep-disordered breathing
Even though these different conditions have unique names, they all share a common trait – they can cause abnormal breathing during sleep.
What to expect with Upper Airway Resistance Syndrome
Upper Airway Resistance Syndrome (UARS) is a condition that falls somewhere in between healthy sleep patterns and mild-to-moderate sleep apnea. The patient’s best shot at getting better largely depends on their doctor’s ability to diagnose and treat the condition early. However, research has shown that if UARS is left untreated, it may increase the risk of high blood pressure. Furthermore, UARS can progress into obstructive sleep apnea, especially if the patient gains weight or has other health conditions as they age.
Possible Complications When Diagnosed with Upper Airway Resistance Syndrome
Continuous interruptions in breathing during sleep can lead to repeated waking up due to increased efforts to breathe, causing fragmented sleep. This phenomenon, known as upper airway resistance syndrome (UARS), can lead to extreme tiredness during the day. Prolonged periods of limited airflow during sleep can cause increased levels of carbon dioxide, leading to possible daytime symptoms and impaired brain function. If UARS is not diagnosed and treated, patients can experience a lower quality of life and symptoms such as fatigue, insomnia, and depression.
A research study from Peru compared patients with UARS with individuals having obstructive sleep apnea (OSA) and the general population. The study showed that those with UARS have a lower quality of life, similar to those with OSA, but significantly below the general population. It also showed that symptoms like muscle pain, the use of psychotropic drugs, obesity, and depression were linked with lower quality of life scores for individuals with UARS. Additionally, untreated UARS can lead to high blood pressure and severe heart conditions, even without any significant reduction in oxygen levels.
A key characteristic of UARS patients is a condition that can cause a shift in the heart chamber wall between heartbeats, along with a drop in blood pressure during inspiration. These are caused by the long-lasting periods of limited airflow experienced by the patient during sleep. These periods can slightly increase carbon dioxide levels, which can trigger the sympathetic nervous system activity and raise the risk of high blood pressure.
Common Symptoms:
- Repeated waking up due to increased efforts to breathe
- Extreme tiredness during the day
- Inability to focus or think clearly
- Fatigue
- Insomnia
- Depression
- Muscle pain
- Use of psychotropic drugs
- Obesity
- Low quality of life
- High blood pressure
- Severe heart conditions
Preventing Upper Airway Resistance Syndrome
When dealing with upper airway resistance syndrome, it’s important for doctors to discuss with patients about their condition. They would use simple, everyday language to explain the problem and its possible effects on the patient’s health. They will also discuss different treatments available to the patient. If the treatment involves using special equipment, like a CPAP machine or mouth devices, the doctor will show the patient how to use them properly. Of course, throughout this process, the doctor will answer any questions the patient may have.
