Inhibitory Effect of Olfactory Stimuli on Sleep Bruxism

Sleep bruxism (SB) is a type of sleep disorder. Because pharmacotherapy for sleep disorders (sleeping drugs, antidepressants etc.) is associated with strong side effects, a complementary therapy in the form of olfactory stimulation with aromas was focused on. The purpose of this study was to investigate how olfactory stimulation with aromas affects SB. The subjects were 26 healthy, dentulous individuals (male: 21, female: 5, mean age: 24.8±3.2 years). Before starting the experiment, SB was confirmed in all 26 subjects using polysomnography (PSG) during nighttime sleep. Lavender (LA) was used for olfactory stimulation, and deionized water was used as the control (CO). The 26 subjects were randomly divided into the LA group and the CO group, and a crossover test, in which olfactory stimulation alternatingly administered, was performed. To eliminate the influence of initial night effects and obtain baseline data, PSG and masseter electromyography (EMG) measurements were performed using a portable high-precision EMG device on three consecutive nights. When crossing over, to eliminate any carry-over effects of each condition, the olfactory stimulation type was switched after a 1-week washout period, and PSG and EMG measurements were performed in the same manner over two consecutive nights. Sleep variables were evaluated with PSG analysis, and the number of SB events was calculated based on masseter EMG analysis. This resulted in the following conclusions.1. Olfactory stimulation with LA improved the sleep state significantly for five of six sleep variables.2. As compared to the baseline and the CO group, the number of SB events in the LA group decreased significantly.3. Results suggested that olfactory stimulation using LA may reduce the number of SB events regardless of a subjective sense of favorable or poor sleep.The results demonstrated the possibility that olfactory stimulation with applying LA improves the sleep state while reducing the number of SB events.