Participants

This study used aggregated data from the 2007–2009, 2010–2012, and 2013–2015 cycles of the KNHANES. The KNHANES is a national cross-sectional survey gathered annually by the Korea Centers for Disease Control and Prevention, and is designed according to multistage stratified and cluster sampling. The data includes health questionnaire and blood test results. Participants who were at least 18 years old, and who had occupational information were included in this study. Individuals who had Hepatitis B and Hepatitis C were excluded from the analysis. In addition, individuals with missing values for major variables and covariates were also excluded. Finally, 51,402 were excluded from the analysis and a total of 21,951 participants were included in the analysis (Fig. 1).

KNHANES: Korea National Health and Nutrition Examination Survey.