Relationship between Lip Seal Strength, Tongue Pressure, and Daytime Sleepiness in Japanese Workers: A Cross-Sectional Study

Abstract Background: This cross-sectional study aimed to examine the relationship between lip seal strength, tongue pressure, and daytime sleepiness, among Japanese workers. Methods: A self-administered questionnaire composed of Epworth Sleepiness Scale (ESS) was conducted on 496 workers, and excessive daytime sleepiness defined by an ESS score of 11 or over. Lip seal strength and tongue pressure were measured in all participants, and multiple regression analyses were performed to examine the effects of lip seal strength and tongue pressure on daytime sleepiness. Results: The median ESS score was 5.0 (25th, 75th percentile: 2.0, 8.0), and 60 (12.1%) workers with excessive daytime sleepiness. The median lip-seal strength was 13.5 N (11.4, 16.3) and tongue pressure was 41.7 kPa (35.2, 48.3). Workers with excessive daytime sleepiness had significantly lower lip seal strength than did those without after adjustment for age and body mass index (BMI) (β (95% confidence interval): –0.043 [–0.081, –0.004]). However, tongue pressure was not significantly associated with excessive daytime sleepiness after adjustment for age and/or BMI. Conclusions: These results suggest that maintaining moderate lip-seal strength may help prevent excessive daytime sleepiness in Japanese workers regardless of age or BMI.