Legal psychoactive substances as risk factors for sleep-related bruxism: a nationwide Finnish Twin Cohort study.

AIMS Different psychoactive factors including alcohol, coffee and tobacco, are considered as risk factors for bruxism. Often, heavy drinking and generous intake of coffee are correlated with smoking. Interactions between these agents may confound studies. The aim was to investigate the possible independent effects of drinking alcohol and coffee consumption on the occurrence of bruxism. METHODS Data derived from the Finnish Twin Cohort study consisting of 12,502 twin individuals (45.6% men, 54.4% women, mean age 44 years) born during the 1930-1957. The twins responded to a questionnaire sent in 1990 (response rate of 77%) consisting of 103 multiple-choice questions, seven dealing with tobacco use, four on alcohol use, one about coffee consumption and two with bruxism. RESULTS Increasing alcohol intake raised the risk for weekly bruxism even when adjusted for smoking status [heavy drinking odds ratio (OR) 1.9; 95% CI 1.23-2.84, binge drinking OR 1.6; 95% CI 1.28-2.12, and passing-out due to excessive alcohol intoxication at least twice within the previous year OR 1.5; 95% CI 1.09-2.18]. The situation was similar to that for coffee consumption of more than eight cups per day (OR 1.4; 95% CI 1.01-1.98). Interaction analyses for 'smoking with risk factors' revealed no statistically significant interactions. Current smoking was an independent risk factor for bruxism in all models (OR 2.3-2.7). CONCLUSION Given the observed associations between alcohol drinking, binge drinking, passing-out due to excessive alcohol intake and coffee consumption, the results support our hypothesis of an independent association of both alcohol use, and coffee consumption with bruxism.