Sleep bruxism and perceived stress: assessment using salivary cortisol levels, a biomarker of stress

Sleep bruxism (SB) corresponds to physiologically based manducatory muscle reactions, with no identifiable neuropathic cause, in relation to anxiety disorders, respiratory disorders or behavioral "tocs". The aim of this study was to assess the relationship between SB and perceived stress by measuring salivary cortisol levels. The study included 61 consenting adult participants: 31 for the study group (bruxers) and 30 for the control group (no bruxers). The diagnosis of BS was made using a standard bruxism assessment questionnaire defined by the American Academy of Sleep Medicine (AASM). The preliminary diagnosis was confirmed by clinical assessment according to AASM criteria. The BRUXi index, a tool proposed by Orthlieb, was used to determine the intensity of bruxism. Perceived stress was measured using the Perceived Stress Scale questionnaire. Unstimulated whole saliva was collected and morning salivary cortisol levels were determined by ELISA. Non-parametric statistical methods were used to analyze the data. The bruxers (study group) had significantly high levels of mean salivary cortisol (12.3±4.2 ng/mL or 34.5±14.6 nmol/L) than the non-bruxers (control group) (5.3±1.2 ng/mL or 14.5±4.6 nmol/L) (p<0.001). The elevated salivary cortisol level was positively associated with perceived stress and SB (p<0.0001) in the study group. These results suggest that bruxing activity is associated with higher levels of perceived psychological stress and salivary cortisol. Despite the absence of polysomnographic recording for the diagnosis of SB, a positive correlation between SB and salivary cortisol levels was observed in bruxers.