Clinical variables
In all, eight variables were created: four for demographics, three for comorbidities, and one for OSA surgery history. We separated each age group into three subgroups (40-60 years old, Others). Economic status was classified according to income quantiles; the top 30% had high economic status, while the bottom 70% had poor economic status. Residential areas were divided into three subgroups (Seoul, Metropolitan, and Rural). The ICD-10 code for diagnosis and medicine prescribing was used to describe comorbidities such as hypertension (HTN), diabetes (DM), and chronic kidney disease (CKD). OSA surgical history was characterized among OSA patients as those with Q2196, Q2197, Q2195, Q2280, Q2281, Q2300, or Q2310 insurance code records prior to BVFL records.