Study design and participants
We analyzed the Korean National Health Information Database (NHID), which combines information obtained from the National Health Insurance Service (NHIS) collected for claims and reimbursement as well as the results of general health examinations provided to all Korean adults13,14. NHIS is a non-profit, single-payer health care organization administered by the government of South Korea that covers virtually all Koreans (approximately 97% of the Korean population is enrolled in the National Health Insurance program, while 3% is covered by medical aid programs). The NHID includes qualification tables (age, sex, location, socioeconomic status, disability, death), treatment tables (statements, details of treatment and prescription, type of disease), clinic tables, and medical check-up tables. It is recommended that all policyholders undergo a health…
