Introduction
Obstructive sleep apnea (OSA) is a disorder in which multiple upper airways are intermittently blocked during sleep1,2. The estimated prevalence of moderate to severe OSA requiring treatment varies depending on age group and sex, ranging from 3 to 50%3,4. OSA is known to be an independent risk factor for cardiovascular and cerebrovascular diseases, both of which are associated with an individual’s mortality5. Consequently, the importance of OSA diagnosis is steadily increasing.

Recent studies have suggested that chronic intermittent hypoxia due to OSA can activate inflammatory pathways and increase oxidative stress, as indicated by high serum levels of interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor (TNF)-α6,7,8. The systemic inflammatory mechanisms of OSA are well-documented for many chronic diseases such as hypertension, diabetes mellitus (DM), and other metabolic syndromes. It has been suggested that OSA is also associated with chronic inflammatory diseases such as CRS9,10,11. Chronic rhinosinusitis (CRS) refers to the inflammation of the nose and paranasal sinuses. The role of the nose in OSA is already well known because people breathe through the nose during sleep12,13. Moreover, previous studies have reported that OSA and sleep disruption are highly prevalent in patients with CRS14,15. Currently, there is a lack of research assessing how the presence and symptoms of CRS in the general population are related to the STOP-Bang questionnaire.

The gold standard diagnostic tool for OSA is polysomnography16. However, due to limited access to sleep laboratories, OSA is underdiagnosed in the general population17. Therefore, the STOP-Bang questionnaire is widely used as an alternative screening test. The STOP-Bang questionnaire is a concise and easy-to-use screening tool for identifying patients at high risk of underlying moderate to severe OSA15,16. The STOP-Bang questionnaire was designed as a screening tool for OSA, comprising 4 self-reportable factors (STOP: snoring, tiredness, observed apnea, and high blood pressure) and four demographic variables (Bang: body mass index (BMI), age, neck circumference, and gender)18. A STOP-Bang score of 3 or higher demonstrates excellent sensitivity in discriminating mild, moderate, and severe OSA (sensitivity: 84%, 93%, and 100%, respectively in the original validation trial)18,19. The diagnostic accuracy of a STOP-Bang score of 3 or higher in detecting moderate to severe OSA was greater than 0.8018. The significance of STOP-Bang lies not only in its ability to measure the risk of OSA, but also in its role as a predictor of detrimental outcomes such as cardiovascular risk associated with OSA20.

The Korea National Health and Nutrition Examination Survey (KNHANES) is an annual survey conducted by Korea Disease Control and Prevention Agency to assess nationwide health and nutrition statistics21. This nationally representative cross-sectional survey annually includes approximately 10,000 individuals and gathers data on socioeconomic status, health-related behaviors, quality of life, clinical profiles relevant to non-communicable diseases, and other related factors22. The increasing clinical importance of OSA prompted the inclusion of the STOP-Bang questionnaire as a survey item for adults aged 40 and above starting in 2019 (The KNHANES VIII)21.Therefore, the aim of this study was to assess the relationship between OSA risk and CRS by analyzing correlations between the STOP-Bang questionnaire and CRS presence and symptoms in the nationwide study.

Results
Relationship between presence of CRS and STOP-Bang questionnaire
The KNHANES survey period for the STOP-Bang and CRS-related questions was from 2019 to 2021. Out of the 22,559 individuals sampled during this period, 9,541 who did not complete the STOP-Bang questionnaire and an additional 2937 individuals who did not complete the CRS-related questionnaire were excluded. Therefore, a total of 10,081 subjects were included in this study. The final sample consisted of 390 (3.9%) individuals with CRS and 9691 individuals without CRS (Fig. 1). The median STOP-Bang score was 3.0 for patients with CRS (Mean ± standard deviation; 2.8 ± 1.6) and 2.0 for those without CRS (2.5 ± 1.5) (Fig. 2). The power size was 0.963. CRS patients exhibited higher percentages of snoring (25.4%), tiredness (46.2%), observed apnea (11.3%), and thick neck circumference (41.8%) compared to subjects without CRS (17.3%, 27.0%, 7.8%, 35.2%, respectively). However, age was significantly lower in patients with CRS (median age, with CRS: 58.0, without CRS: 60.0; P < 0.001). Additionally, the percentage of individuals over the age of 50 was significantly higher in the CRS group. This contrasts with the known association of increasing age with a higher risk of OSA (Table 1). Cigarette smoking was significantly (49.2% of CRS patients and 39.6% of subjects without CRS; P < 0.001) more prevalent in the CRS group, while alcohol use was not significantly (P = 0.161) different between the two groups. Asthma and AR were significantly more prevalent in the CRS group (Asthma: 9.4% of CRS patients and 3.0% of without CRS subjects; AR: 49.7% of CRS patients and 11.0% of without CRS subjects). There were no significant differences in house income (P = 0.212) or economic activity (P = 0.128). However, education level was higher in the CRS group (73.3% of CRS patients are highly educated level, compared to 65.5% of subjects without CRS; P = 0.003).

Additionally, our study is the first to investigate specific symptoms of CRS in relation to OSA, while also identifying which components of the STOP-Bang questionnaire are associated with CRS in the general population. Among the four symptoms of CRS (nasal congestion, discharge, facial pain/pressure, and decreased sense of smell), nasal congestion and decreased sense of smell were increased in the high risk group. According to a previous study, participants with these typical CRS symptoms had an increased risk of various sleep-related problems such as snoring, difficulties in initiating sleep, difficulties in maintaining sleep, early morning awakening, and excessive daytime sleepiness compared to those without CRS symptoms15. Interestingly, within the STOP-Bang questionnaire, we found positive correlations of CRS with snoring, tiredness, and observed apnea. This finding suggests that airflow disturbance can increase the risk of OSA in CRS patients, providing additional information beyond previous studies that suggest a potential link between the two conditions through shared systemic inflammatory pathophysiological mechanisms9. We did not observe significant differences in hypertension, BMI, or sex among components of the STOP-Bang questionnaire for CRS patients. Similarly, a previous study has shown that patients with CRS tend to exhibit a higher risk of OSA even with lower BMI levels23. Our data showed that patients with CRS were relatively younger in age, despite the well-established association between increasing age and a higher risk of OSA24. Nevertheless, CRS patients still had a higher risk of OSA.

CRS is a heterogeneous multifactorial disease25. It is known to be associated with microbial infections, smoking, pollutants, allergens, and other social factors such as a correlation with low socioeconomic status26,27. However, in our study, it was not related to household income or economic activity. The prevalence of CRS was higher in the group with higher education. Regarding comorbidities of CRS, previous research has indicated that the presence of persistent AR in addition to CRS can further amplify the risk of sleep problems15. Moreover, conditions that are well-known risk factors for OSA, such as AR and asthma, were found to be more prevalent in patients with CRS. The presence of these conditions, which are frequently observed in CRS, is considered to increase the risk of OSA. CRS is classified into type 2 and non-type 2 according to endotypes28. In Korea, there has been an eosinophilic shift, and the prevalence of type 2 CRS is increasing29,30. Comorbidities such as AR and asthma are also on the rise, which may increase the risk of OSA.

The association between CRS and OSA is complex. Although such association is not fully established yet, some studies have suggested that these two conditions might be bidirectionally related. As mentioned earlier, CRS has been identified as a risk factor for OSA. However, some studies also suggest that OSA may increase the development of CRS31. According to Garvey et al., patients with both CRS and OSA show higher rates of antibiotic and steroid usage than those with CRS alone31. In particular, among the group of patients with both OSA and CRS who did not receive continuous positive airway pressure or sleep surgery, the likelihood of using antibiotics or steroids remained higher even when compared to groups receiving similar rates of endoscopic sinus surgery31.

A limitation of our study was that it was designed as a cross-sectional study, making it difficult to establish causal relationships. However, in our research, CRS treatment status did not significantly correlate with the OSA risk. Additional study is needed to further investigate this. Another limitation of our study was that the KNHANES included the STOP-Bang questionnaire only for individuals aged 40 and above. Consequently, our study was limited to participants within this age group, and the findings may not be representative of all age groups. Additionally, we did not diagnose OSA through objective tests but relied on a questionnaire-based approach. To enhance the reliability of our findings, we utilized various indicators from multiple questionnaires. Furthermore, since this study relied on survey data, defining CRS through endoscopic or CT findings was not possible, nor was obtaining nasal tissue for endotyping. Future prospective studies should incorporate endoscopic examinations, CT scans, and tissue sampling from participants to address these limitations.

Conclusions
Our study showed that the subjects with CRS had significantly higher STOP-Bang questionnaire score. This finding was associated with increased occurrences of snoring, tiredness, and apnea. Among symptoms of CRS, nasal obstruction and decreased sense of smell were found to be linked to an increased risk of OSA.