Investigation of the relationship between sleep disorders and xerostomia.

OBJECTIVES: To investigate the relationship between sleep disorders, morning hyposalivation, and subjective feeling of dry mouth. MATERIALS AND METHODS: A cross-sectional, observational, clinical study was carried out in a homogenous population sample which consists of Greek male soldiers without any medical history. After the application of oral modified Schirmer test, the sample was divided into a study group (n = 63) (MST < 25 mm/3 min) and a control group (n = 110) (MST ≥ 25 mm/3 min). In order to assess daytime sleepiness, risk of obstructive sleep apnea (OSA), sleep quality, sleep bruxism (SB), and subjective feeling of dry mouth, all the participants filled in the following scales in Greek version: Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Index (PSQI), Berlin Questionnaire (BQ), a SB questionnaire, and Xerostomia Inventory (XI) respectively. In every subgroup that came of ESS, PSQI, BQ, and SB questionnaire scoring, subjective feeling of dry mouth was evaluated, based on XI values. RESULTS: Statistically significant difference (p < 0.001) through PSQI scores was found between the study and control group. In contrast, a statistically significant difference was not obtained for the scores of ESS (p = 0.293), BQ (p = 0.089), and SB questionnaire (p = 0.730). XI scores introduced statistically significant difference between the subgroups of PSQI (p < 0.001), BQ (p = 0.001), SB questionnaire (p = 0.004)  and statistically weak between the subgroups of ESS (p = 0.049). CONCLUSIONS: This is the first research study so far suggesting that patients with morning hyposalivation exhibit poor sleep quality using an objective method. The present results have, also, shown that subjective feeling of dry mouth is related to excessive daytime sleepiness, poor sleep quality, high risk of obstructive sleep apnea, and sleep bruxism, but larger-scale studies are still needed. CLINICAL RELEVANCE: These findings should keep dentists aware of a possible association between xerostomia and sleep disorders and support larger-scale studies.