Healthcare system in Korea
Since 2000, various health insurance systems in South Korea have merged into a single system run by the National Health Insurance Service (NHIS). Consequently, most people living in South Korea are currently insured by the NHIS. Our study data were collected from the Korea National Health Insurance (KNHI) claims database from 2007–2015. In Korea, 97% of the population is obligated to enroll in the KNHI program; the remaining 3% are under the Medical Aid Program. Therefore, the KNHI claims database contains information on all claims for approximately 50 million Koreans, and almost all information about disease incidence can be obtained from this centralized database, with the exception of procedures not covered by insurance, such as cosmetic surgery.