After talking in one's sleep and snoring, the grinding and clenching of teeth--a condition known as sleep bruxism--is the third most common sleep disorder, according to the results of a new study. In fact, more than 8 percent of the population grips and grates their teeth together during sleep at least once a week, researchers write in the January issue of the journal Chest. Half of these people reported having abnormal tooth wear or muscular discomfort, or grinding their teeth so intensely that their bed partners could hear it. What is more, sleep bruxism appears to be associated with other sleeping and mental disorders.

Stanford University researcher Maurice M. Ohayon and his colleagues analyzed data collected from more than 13,000 participants in Italy, Germany and the U.K. The team found that those people who grind their teeth are significantly more likely to suffer from snoring and sleep apnea (a disorder characterized by temporary interruptions in breathing), as well as anxiety disorders and hallucinations, than are non-grinders. And around 69 percent of those individuals with sleep bruxism linked their condition to either stress, anxiety or aggravation. The new data further indicate that bruxism is unrelated to gender, and that it decreases significantly with age.

Ohayan recommends that general practitioners and dentists inquire about bruxism and sleep apnea if they observe abnormal tooth wear damage in a patient, noting that "further research is necessary on the pathophysiologic mechanisms of this largely unknown sleep disorder."