[Clinical and salivary metabolomic characterization of patients with OSA comorbid with LPRD]

Objective: To explore the clinical and salivary metabolic component characteristics of patients with OSA combined with LPRD, and to investigate the potential co-morbid mechanisms of LPRD and OSA. Methods: A total of 98 adult patients with OSA (81 males and 17 females) who visited the Department of Otolaryngology of Peking University Third Hospital from March 2024 to May 2024 were consecutively included. The age ranged from 19 to 68 years (mean±standard deviation: 39.44±11.39 years). The severity of OSA was grouped according to the apnea-hypopnea index (AHI) [mild group (29 cases), moderate group (26 cases), and severe group (43 cases)]. Patients with a reflux symptom index score (RSI)>13 points and/or a reflux sign score (RFS)>7 points were considered LPRD positive. Among the 98 OSA patients, 48 had LPRD and 50 did not. All patients were diagnosed with OSA through out of center sleep testing(OCST) or polysomnography (PSG), and general information, laryngoscopic examination images, and RSI scales were collected. The RFS was evaluated based on the laryngoscopic examination results. Saliva samples were collected from both groups for metabolomics analysis. Chi-square test was used for categorical variable comparison, and independent sample t-test or one-way ANOVA analysis of variance was used for continuous variable comparison. Results: Stratified analysis showed that the proportion of male patients in the mild OSA group was significantly lower than that in the moderate or severe OSA groups (58.6%, 92.3%, 93.0%, χ²=16.43, P<0.001), and the BMI was significantly lower in the mild OSA group [(25.80±4.41)kg/m², (27.53±3.88)kg/m², (28.99±3.65)kg/m², F=6.91, P=0.002]. There was no statistically significant difference in the prevalence of LPRD among patients with different severity of OSA. The BMI of OSA patients with LPRD was higher than that of patients with OSA alone [(28.65±4.75)kg/m², (26.94±3.16)kg/m², t=-2.07,P=0.041], but there were no statistically significant differences in gender composition, age, AHI, and minimum blood oxygen saturation between the two groups. The metabolomics results of saliva samples from both groups showed significant differences in the levels of tryptophan pathway metabolites. The salivary serotonin metabolite level in patients with LPRD combined with OSA was significantly lower than that in patients with OSA alone (relative abundance 0.12±0.019 vs 0.22±0.046, t=2.04,P=0.045). Conclusion: Patients with OSA combined with LPRD have a greater BMI and significantly lower serotonin, a tryptophan metabolite component of saliva, which may be a potential co-morbidity mechanism between OSA and LPRD.