Sleep bruxism frequency and platelet serotonin transporter activities in young adult subjects

Purpose: To evaluate correlations between serotonin transporter (SERT) uptake ability in human peripheral platelets and sleep bruxism (SB) frequency. Methods: Subjects were consecutively recruited from sixth-year students at Okayama University Dental School. Subjects were excluded if they (1) were receiving orthodontic treatment, (2) had a dermatological disease, (3) had taken an antidepressant within 6 months, or (4) had used an oral appliance within 6 months. SB frequency was determined as the summary score of three consecutive night assessments using a self-contained electromyography detector/analyzer in their home. Fasting peripheral venous blood samples were collected in the morning following the final SB assessment. SERT amount and platelet number were quantified via an ELISA assay and flow cytometry, respectively. Functional SERT characterization, 5-hydroxytryptamine (5-HT) uptake, maximum velocity (V_max), and an affinity constant (K_m) were assessed with a [³H] 5-HT uptake assay. The correlations between these variables and SB level were evaluated. Results: Among 50 eligible subjects (26 males, mean age 25.4 ± 2.41 years), 7 were excluded because of venipuncture failure, smoking, and alcohol intake during the experimental period. A small but significant negative correlation between SB level and [³H] 5-HT uptake was observed (Spearman’s correlation R² = 0.063, p = 0.04). However, there were no significant correlations between SB level and total platelet amount, SERT, V_max, and K_m values (p = 0.08, 0.12, 0.71, and 0.68, respectively). Conclusions: Platelet serotonin uptake is significantly associated with SB frequency, yet only explains a small amount of SB variability.