Methods
Study data were collected from the Korea National
Health Insurance (KNHI) Claims Database of the Health
Insurance Review and Assessment Service (HIRA) for
2006–2010. In Korea, 97% of the population is obligated
to enroll in the KNHI program. Healthcare providers are
required by the health insurance policies to allow HIRA
to review the medical costs incurred. The remaining 3%
of the population is under the Medical Aid Program.
Thus, the HIRA database contains information on all
claims for approximately 50 million Koreans, and nearly
all information about the volume of disease can be ob-
tained from this centralized database with the exception
of procedures that are not covered by insurance, such as
cosmetic surgery. Many epidemiological analyses have
been published from this database. According to the Act
on the Protection of Personal Information Maintained
by Public Agencies, HIRA prepares the claims data by
concealing individual identities. Studies using data can,
therefore, be exempt from institutional review board re-
view [16]. The database we received included an uniden-
tifiable code representing each individual together with
age, diagnosis, and a list of prescribed procedures.