"Secondhand smoke exposure" induces "sleep bruxism" through "poor sleep quality".

July.06.2020RESEARCH HIGHLIGHTS

Release Subtitle: Associations between secondhand smoke, sleep quality, and sleep bruxism.

Release Summary Text:
Sleep bruxism is non-functional activity and sometimes harmful to oral health. Present study reports that association between secondhand smoke, sleep bruxism, sleep quality and sleep quality in Japanese young adult females. Poor sleep quality is indirectly associated with secondhand smoke through it. So, we should pay attention to a new harmful aspect of secondhand smoke exposure for good sleep and healthy life

Full text of release:
Highlight
・Sleep quality was directly associated with secondhand smoke (SHS) exposure in females.
・SHS exposure was indirectly associated with sleep bruxism in females.
・No associations were observed in males between SHS exposure, sleep quality and sleep bruxism.

Introduction
Sleep bruxism, a major sleep disorder that adversely affects oral health, is defined by the American Academy of Sleep Medicine as “repetitive jaw muscle activity characterized by the clenching or grinding of teeth and/or bracing or thrusting of the mandible”. It can lead to tooth wear, tooth or restoration fracture, hypersensitive or painful teeth, loss of periodontal support, pain in the temporomandibular joint or jaw muscles, headaches, and masticatory muscle hypertrophy [Beddis et al, 2018]. Thus, dentists often encounter the adverse effects of sleep bruxism in the clinical setting.

Sleep bruxism is considered a multifactorial disease. Some studies have reported risk factors for sleep bruxism, including gender, age, alcohol drinking, gastroesophageal reflux disease, and disorders of the dopaminergic system [Câmara-Souza et al, 2019]. However, the causes of sleep bruxism remain unclear.

Smoking is also known to be a risk factor for sleep bruxism [Rintakoski et al, 2010] and to affect sleep quality adversely [Purani et al, 2019]. Tobacco smoke includes over 4000 chemicals, more than 200 of which are harmful [Roemer et al, 2004]. Sleep bruxism can be induced by smoking, which also adversely affects sleep quality. Smokers can harm health of their family as well as own health. However, the effect of secondhand smoke (SHS) exposure on sleep quality and sleep bruxism remain unclear. The objective of present study was to clarify the associations between sleep bruxism, sleep quality, and SHS exposure.

Methods
The inclusion criteria were adults aged between 18 and 19 years, non-smokers and non-alcohol drinkers. The exclusion criteria were failing to complete the questionnaire in full. We performed oral examinations and self-questionnaires for Japanese university students, and then assessed SHS exposure, sleep quality, and sleep bruxism, as shown below:
・SHS exposure
Q. Does anyone in your family smoke? (current smoker/past smoker/nonsmoker)
・Sleep quality
The Japanese version of the Pittsburgh Sleep Quality Index (PSQI-J) (score: 0-21).
The score >5 was considered “poor sleep”.
・Sleep bruxism
The third edition of the International Classification of Sleep Disorders (ICSD-3).
In self-administered questionnaires, we asked “Has anyone heard you grinding your teeth while you were asleep at night? (yes/no)”, “How often is your jaw fatigued or sore on walking in the morning? (frequently/sometimes/rarely/never)”, “How often do you have a temporal headache in the morning? (frequently/sometimes/rarely/never)”.
・Other
Gender, age, smoking and drinking status

Results
A total of 1781 Japanese young adults (970 males [54.5%] and 811 females [45.5%]) were analyzed in present study. Young adult females who had been exposed to SHS had worse sleep quality than those who had not. Young adult females with worse sleep quality showed higher prevalence of sleep bruxism than those with better sleep quality. Finally, we showed that SHS exposure was indirectly associated with sleep bruxism through poor sleep quality in Japanese young adult females. However, no association was found among young adult males between SHS exposure, sleep quality, and sleep bruxism.

Conclusion
SHS exposure indirectly related to sleep bruxism via poor sleep quality among Japanese young females. The specific point of present study is that SHS exposure influenced sleep quality and oral health. As SHS exposure is a main topic in public health, we should pay attention to a new harmful aspect of SHS exposure for getting good sleep and healthy life.

Author comment
Toyama said “I emphasize that SHS exposure can influence sleep quality and oral health from our study. In Japan, smoking in public places is prohibited to prevent secondhand smoke exposure from April 2020. I think that secondhand smoke exposure at home is also mattered. I hope that the present study is a chance to think about risks of SHS at home. Then, in the near future, I believe that there are no children and adolescents who experience undesired SHS exposure all over the world.”

DoI: 10.1016/j.sleep.2019.09.003

Contact Person: TOYAMA Naoki

Reference:
Title of original paper: Associations Between Sleep Bruxism, Sleep Quality, and Exposure to Secondhand Smoke in Japanese Young Adults: A Cross-Sectional Study
Journal: Sleep Medicine
DOI: http://dx.doi.org/10.1016/j.sleep.2019.09.003[New window]

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