Some sleeping problems tend to go unnoticed. If the main symptoms can’t be perceived by a person when they are sleeping, they may not be aware of the problem.
That is the case for both obstructive sleep apnea (OSA) and sleep-related bruxism. OSA is a disorder characterized by diminished oxygenation with or without awakening due to increased breathing effort as the upper airway becomes obstructed to some degree. One’s bed partner may report loud snoring, gasping, choking, snorting or interruptions in breathing while sleeping. Sleep-related bruxism involves repetitive jaw-muscle activity during sleep, often characterized by teeth grinding or clenching.
With a broad definition, OSA has been estimated to affect approximately 15-30% of males and 10-30% of females. Using a more restrictive definition, 2-9% of adults are affected and 2–5% of children at any age however, it is often believed to be underdiagnosed. Sleep-related bruxism may affect up to 50% of children, around 15% of adolescents, 8% of middle-aged adults, and 3% of elderly people.
In addition to looking at their prevalence independently, studies have found that a surprising number of people have both OSA and sleep-related bruxism. In fact, one of the main risk factors for sleep-related bruxism is OSA. To date, though, it’s still unclear whether there is causation or only correlation.
There are several potential explanations for the co-occurence of OSA and sleep-related bruxism. These hypotheses are explained in the following sections, but further research will be necessary to clarify the nature of the relationship between these conditions.
Multiple types of research studies have found a higher-than-expected percentage of people have both OSA and sleep-related bruxism.
Epidemiological studies, which examine patient records and datasets, identified that many people with OSA were also prone to grind their teeth. Though not all of these studies have found the same rates of co-occurrence, a general pattern emerged showing a correlation between teeth grinding and sleep apnea.
The same correlation has also been found in studies using polysomnography, which is a type of in-depth sleep study done in a specialized clinic. Because it involves close observation of a sleeper, polysomnography provides greater confidence than some other studies that rely on surveys of self-reported sleep apnea or teeth grinding.
While research studies have shown a correlation between sleep apnea and sleep-related bruxism, they don’t clearly explain the underlying nature of that association.
Sleep scientists have formulated several hypotheses about how these conditions are connected. These hypotheses include that OSA triggers sleep-related bruxism, that sleep bruxism triggers OSA, that they occur independently, and that they are involved in a complex and multidimensional relationship.
The following sections review these hypotheses, but it is important to highlight that research so far has not been able to establish any of them as definitive or to show conclusively that there is a direct connection between teeth grinding and sleep apnea.
One hypothesis holds that sleep apnea gives rise to episodes of teeth grinding. The concept behind this view is that teeth grinding occurs as a response to the pauses in breath that happen because of OSA.
Some argue that when the airway becomes constricted from OSA, movement of the muscles of the mouth that are involved in chewing, may help to reopen it leading to teeth grinding. Another possibility is that the clenching and grinding helps to lubricate the tissue in the back of the throat that can become dried out from labored breathing from sleep apnea.
In this view, sleep-related bruxism is seen as part of the body’s response to try to protect itself from the effects of OSA. Even though it may not apply to all people with OSA, this hypothesis may describe a subset of OSA patients who experience teeth grinding subsequent to disturbed breathing episodes during sleep.
A less common view is that sleep bruxism may be a contributing factor to sleep apnea. The underlying mechanism by which this may occur has to do with signals from the nervous system that affect heart rate, muscles around the jaw, and the nasal passages. Signals that initiate teeth grinding may also increase congestion and airway restriction, creating disordered breathing.
A challenge to this view is that sleep studies of people with both sleep-related bruxism and OSA have found that teeth grinding episodes precede OSA-related breathing episodes only about 25% of the time.
Another potential explanation is that OSA and sleep-related bruxism are correlated but that there is no causal link from one to the other. Instead, the two conditions arise independently of one another, although they could both be related to another, separate cause.
An argument in favor of this hypothesis is that OSA and teeth grinding episodes don’t follow a consistent sequence. If there were a strong causal relationship, you would expect to see one type of episode almost always follow the other.
But that type of clear pattern hasn’t been found in studies to date. While it is more common for teeth grinding to happen shortly after disrupted breathing, it can also happen before. And at other points during sleep, a person may grind their teeth or have disordered breathing without the other issue arising.
Given this inconsistency, a separate mechanism may influence the development of OSA and sleep-related bruxism and make them more likely to co-occur. Early research has identified abnormalities in pathways of dopamine and serotonin, chemicals of the nervous system known as neurotransmitters, as one possible underlying mechanism.
According to some expert opinions, there is a multifaceted and complex relationship between sleep apnea and teeth grinding that can manifest in distinct ways in different individuals.
OSA is a complicated disorder that involves the nervous, cardiovascular, and respiratory systems. It can be tied to both genetic and environmental factors as well as a person’s weight, anatomy in the head-and-neck region, sleeping position, among other influences. Similarly, there can be diverse contributing factors to sleep bruxism.
Given the complexity of these conditions, the most plausible explanation is that there is no direct, causal relationship between the two in all cases. Instead, different subsets of patients may reflect elements of each hypothesis, which could explain the inconsistent and inconclusive findings in research studies conducted so far.
Until future research uncovers the exact nature of the relationship between sleep apnea and sleep-related bruxism, it is hard to know whether the correlation between them is clinically important.
In the meantime, people who have OSA or sleep-related bruxism should be aware that they may occur together. This can help them be on the lookout for symptoms and raise the issue with their doctor who can determine whether further testing or treatment would be beneficial.
When both conditions are present, their identification may play a role in optimizing treatment. For example, a case study revealed that therapy with a positive airway pressure (PAP) device, successfully treated both conditions. In addition, some mouthpieces, such as mandibular advancement devices (MADs) that hold the tongue and lower jaw forward, may help treat OSA and also reduce teeth grinding.