Bruxism is associated with nicotine dependence: a nationwide Finnish twin cohort study.
OBJECTIVE
To investigate the association of smoking with bruxism while controlling for genetic and environmental factors using a co-twin-control design. Especially, the role of nicotine dependence was studied in this context.


METHODS
The material derives from the Finnish Twin Cohort consisting of 12,502 twin individuals who responded to a questionnaire in 1990 (response rate of 77%). All were born in 1930-1957, the mean age being 44 years. The questionnaire covered 103 multiple choice questions, 7 dealing with tobacco use and 22 with sleep and vigilance matters, including perceived bruxism. In addition, a subsample derived from the Nicotine Addiction Genetics Finland Study containing 445 twin individuals was studied.


RESULTS
In age- and gender-controlled multinomial logistic regression, both monthly and rarely reported bruxism associated with both current cigarette smoking (odds ratio [OR] = 1.74 and 1.64) and former cigarette smoking (OR = 1.64 and 1.47). Weekly bruxism associated with current smoking (OR = 2.85). Current smokers smoking 20 or more cigarettes a day reported weekly bruxism more likely (OR = 1.61-1.97) than those smoking less. Among twin pairs (N = 142) in which one twin was a weekly bruxer and the cotwin a never bruxer, there were 13 monozygotic pairs in which one twin was a current smoker and the other twin was not. In all cases, the bruxer was the smoker (p = .0003). Nicotine dependence associated significantly with bruxism.


CONCLUSIONS
Our twin study provides novel evidence for a possible causal link between tobacco use and bruxism among middle-aged adults. Nicotine dependence may be a significant predisposing factor for bruxism.
Institute of Dentistry, University of Helsinki, PL 41, Helsinki 00014, Finland. katariina.koivumaki@helsinki.fi
K
K
Rintakoski
J
J
Ahlberg
C
C
Hublin
U
U
Broms
P A F
PA
Madden
M
M
Könönen
M
M
Koskenvuo
F
F
Lobbezoo
J
J
Kaprio
D000368:Aged; D002012:Bruxism / Q000453:epidemiology*; D015984:Causality; D015331:Cohort Studies; D015897:Comorbidity; D004200:Diseases in Twins / Q000453:epidemiology; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D012907:Smoking / Q000453:epidemiology*; D014029:Tobacco Use Disorder / Q000453:epidemiology*; D014427:Twins