2.1 | Study design and participants
This study was designed as a secondary data analysis using and
interpreting data drawn from the third through thirteenth Korean Youth
Risk Behavior Web-based Surveys (KYRBSs) completed across 7 years from
2013 to 2019. KYRBS was initiated by the Korean Ministry of Education,
Ministry of Health and Welfare, and Centers for Disease Control and
Prevention (KCDC) in 2005. The KYRBS is a cross-sectional,
self-administered, anonymous, online survey that is conducted annually
in a nationally representative sample of Korean adolescents aged 12–18
years. The Institutional Review Board (IRB) of the KCDC approved this
online statistical research during the entire survey every year. In
order to obtain a nationally representative sample, the KYRBS used the
stratified three stage random cluster sampling method, which included
stratification, sample allocation, and stratified cluster sampling, as
is described. The study population was stratified by geographic region
and school type to minimize sampling error. In sample allocation, 400
middle schools and 400 high schools were selected by proportional
sampling to match the study population every year. In stratified cluster
sampling, sample classes were selected by simple randomization sampling
from the selected schools. All of the participants provided written
informed consent (both directly and from their parents or legal
guardians) for approval of survey access. Every student participated
voluntarily and completed the survey by logging on to the survey’s
Internet webpage at their school’s computer laboratory using a randomly
assigned unique identification number. The participants were not able to
skip to subsequent questions without providing proper answers to every
question. The online system does not accept omitted responses. Data were
considered to be missing if there was any logical error or if there was
outlier. In the present study, we obtained the raw data that are
publicly available from the online site of KYRBSs
(https://www.cdc.go.kr/yhs/home.jsp). The reasons for drop-out or
non-participation were not available. Our study protocol for secondary
analysis and interpretation was reviewed and approved by the IRB of
Samsung Changwon Hospital (IRB No. 2020-06-009).