Population of this study
This study passed the scrutiny of the Institutional Review Board of
Jeonbuk National University Hospital (IRB number 2020-08-012). This time
series analysis was conducted using the anonymized Korea National Health
Insurance Service-National Sample Cohort (KNHIS-NSC) database, and data
in the period from January 1, 2007 to December 31, 2012 were analyzed.
This database includes day of hospital visit, the patient’s age, sex,
residential area, economic level, diagnosis, medical history, and
disease code. The diagnostic codes from KNHIS-NSC are based on the
International Classification of Diseases, Tenth Revision (ICD-10). In
2007, the population in Korea was 49,194,085, of which 1 million cohorts
of randomly stratified samples were used by the KNHIS-NSC databases.
The inclusion criteria of the CE population from this database were: 1)
patients assigned code J441 in the ICD-10 classification at the time of
the hospital visit; 2) patients taking oral steroids; and 3) patients
with chest computed tomography scans.5,6 Individuals
were divided into four age groups: preschool age (0 to 4 years old),
school age (5 to 19 years old), adult (20 to 59 years old), and elderly
(≥60 years old).