Grinding of Teeth (Bruxism) During Sleep Associated with Other Disorders

The grinding or clenching of teeth during sleep on a weekly basis affects more than 8% of the population and is associated with other disorders such as daytime sleepiness and anxiety, according to a new study. The study, based on 13,057 participants in Italy, Germany, and the United Kingdom, was reported in the January issue of CHEST, the peer-reviewed journal of the American College of Chest Physicians.

The condition is known as sleep bruxism, an oral habit characterized by rhythmic activity of the jawbone muscles that cause a forced contact between dental surfaces during sleep. It has been linked to headaches, joint discomfort and muscle aches, premature loss of teeth, and sleep disruption for both the person with bruxism as well as his or her bed partner.

Study Methodology

The study, carried out in the three European countries, aimed to document the prevalence of sleep bruxism in the general population, the risk factors associated with the disorder, and its links to other health-related and sleep-related issues.

Prevalence is the estimate of a disease as a whole in a given population in a given time. It is usually based on a set of criteria for that disease that can be utilized in a questionnaire administered on a large scale. It does not require clinical evaluations.

The International Classification of Sleep Disorders (ICSD) suggests the following as minimal criteria for sleep bruxism: the presence of teeth grinding during sleep and, at least one of the following associated features - abnormal tooth wear, muscular discomfort, or sound associated with the tooth grinding. The participants in the study were divided into one of three groups: those who met the ICSD criteria, those with tooth-grinding alone, and those without tooth grinding.

Participants were interviewed by phone, with interviews averaging 40 minutes in length. The information gathered was entered into a Sleep-EVAL system, a software system designed to conduct epidemiologic studies on sleep, sleep habits, and mental disorders in the general population. Validation of the data was conducted at Stanford University's Sleep Disorder Center in Palo Alto, California and the Regensburg University Sleep Disorders Center in Germany.

Tooth grinding during sleep is classified as one of the parasomnias by the ICSD. It is found most often in non-REM sleep stages, mostly in stage 2, although it can occur in REM sleep.

Study Findings

Tooth grinding which occurred at least weekly during sleep was reported by 8.2% of the participants. More than 54% of those with tooth grinding reported some related problem, including 23% who said they needed dental work because of the grinding and 8% who claimed discomfort of their jaw muscles upon awakening. More than 23% said the grinding was loud enough for bed partners to hear it. The total, then, for all those in the study population who met the ICSD criteria was 4.4%, suggesting that bruxism is the third most common form of parasomnia following talking in one's sleep and snoring.

Snoring, breathing pauses during sleep, and obstructive sleep apnea were significantly more frequent in the sleep bruxism group and the tooth-grinding alone group than in the rest of the participants. The sleep-bruxism group reported significantly more frequent episodes of nocturnal awakenings, morning headaches, and a subjective sense of blocked breathing and choking during sleep. Obstructive sleep apnea showed a prevalence of 4.8% in the sleep-bruxism group, 3.4% in the tooth-grinding alone group, and only 1.4% in the non-tooth-grinding group.

The relationship between obstructive sleep apnea and sleep bruxism is usually related to an arousal response. The ending of an apneic event may be accompanied by a number of mouth phenomena, such as snoring, gasps, mumbles, and tooth grinding.

Sleep bruxism was also associated with daytime sleepiness. About one third of the bruxism group reported being sleepy during the day. There was no significant association with other sleep disorders, such as insomnia, restless legs syndrome, or periodic limb movement disorder.

Mental disorders, mainly anxiety disorders and hallucinations, were also significantly related to tooth grinding during sleep. About 69% of those with sleep bruxism related their condition to aggravation, stress, or anxiety. Daily use of alcohol, tobacco, or caffeine was also associated with sleep bruxism.

Researchers also noted that bruxism was unrelated to gender and decreased significantly with age. The highest prevalence was observed in the 19- to 44-year-old group, at 5.8%.

What are the Risks?

Speaking on behalf of his colleagues, Maurice M. Ohayon, M.D., Stanford University School of Medicine, said "the results of this study raise an important concern about the risk of sleep apnea for sleep bruxers. A plausible explanation for this association," he said, "could rely on the shared anatomic problems proposed by some research such as mandibular (jawbone) deficiency, temporomandibular abnormalities, and craniofacial abnormalities."

Dr. Ohayon said that sleep bruxism should be considered in patients with sleep-disordered breathing disorders. He called on general practitioners to inquire about sleep bruxism and sleep apnea symptoms when abnormal tooth wear damage is identified. He also urged dentists to ask about symptoms of sleep-disordered breathing when dental signs of bruxism are present.

"Finally," he said, "further research is necessary on the pathophysiologic mechanisms of this largely unknown sleep disorder."

In Summary

Sleep bruxism is common in the general population, and is the third most frequent parasomnia. Persons with anxiety and sleep-disordered breathing have a higher number of risk factors for sleep bruxism, as do persons with certain other characteristics (see table below).

Characteristics	Odds Ratio for Sleep Bruxism
Obstructive Sleep Apnea	1.8
Loud Snorers	1.4
Moderate Daytime Sleepiness	1.3
Heavy Alcohol Drinkers	1.8
Caffeine Drinkers	1.4
Smokers	1.3
Highly stressful life	1.3
Anxiety	1.3