Table 1. Crude OR difference in pandemic-related factors associated with alcohol use among Korean youth in KYRBS, 2019 versus 2021

Variables	Pre-COVID-19 pandemic (n=55,748)		COVID-19 pandemic (n=53,445)		Ratio of OR† (95% CI)	p-value
	Crude OR (95% CI)	p-value	Crude OR (95% CI)	p-value
Grade
7th–9th grade (middle school)	1.000 (reference)		1.000 (reference)
10th¬12th grade (high school)	3.455 (3.277 to 3.642)	<0.001	3.104 (2.924 to 3.295)	<0.001	0.898 (0.830 to 0.973)	0.008
Sex
Male	1.308 (1.247 to 1.372)	<0.001	1.402 (1.325 to 1.483)	<0.001	1.072 (0.996 to 1.154)	0.066
Female	1.000 (reference)		1.000 (reference)
BMI*, kg/m2	1.057 (1.051 to 1.064)	<0.001	1.049 (1.041 to 1.056)	<0.001	0.992 (0.983 to 1.002)	0.114
Residence
Rural	1.000 (reference)		1.000 (reference)
Urban	1.181 (1.125 to 1.239)	<0.001	1.228 (1.160 to 1.299)	<0.001	1.040 (0.965 to 1.120)	0.304
Current smoking	18.010 (16.681 to 19.446)		20.470 (18.682 to 22.429)	<0.001	1.137 (1.009 to 1.281)	0.035
Depression	2.062 (1.963 to 2.165)	<0.001	2.042 (1.928 to 2.162)	<0.001	0.993 (0.918 to 1.068)	0.800
Highest educational level of parents
College or higher	1.000 (reference)		1.000 (reference)
High school or lower	1.690 (1.586 to 1.801)	<0.001	1.876 (1.748 to 2.013)	<0.001	1.110 (1.009 to 1.221)	0.031
Unknown	1.233 (1.166 to 1.304)	<0.001	1.406 (1.317 to 1.501)	<0.001	1.140 (1.046 to 1.243)	0.003
Economic level
High	1.000 (reference)		1.000 (reference)
Middle-high	0.864 (0.794 to 0.941)	0.001	0.977 (0.881 to 1.084)	0.666	1.131 (0.954 to 1.340)	0.157
Middle	0.924 (0.854 to 1.001)	0.051	1.074 (0.975 to 1.183)	0.151	1.162 (1.026 to 1.317)	0.018
Middle low	1.332 (1.209 to 1.467)	<0.001	1.644 (1.460 to 1.851)	<0.001	1.234 (1.059 to 1.438)	0.007
Low	1.927 (1.659 to 2.239)	<0.001	2.422 (2.031 to 2.889)	<0.001	1.257 (0.997 to 1.584)	0.053
School performance
High	1.000 (reference)		1.000 (reference)
Middle-high	1.013 (0.926 to 1.108)	0.784	1.155 (1.035 to 1.290)	0.010	1.140 (0.989 to 1.314)	0.070
Middle	1.232 (1.131 to 1.342)	<0.001	1.372 (1.236 to 1.524)	<0.001	1.114 (0.973 to 1.275)	0.119
Middle-low	1.668 (1.529 to 1.819)	<0.001	1.857 (1.670 to 2.066)	<0.001	1.113 (0.970 to 1.277)	0.126
Low	2.588 (2.351 to 2.850)	<0.001	2.828 (2.518 to 3.175)	<0.001	1.093 (0.940 to 1.270)	0.249

BMI, body mass index; CI, confidence interval; OR, odds ratios
Body mass index was calculated as weight in kilograms divided by height in meters squared.
Ratio of odds ratios was calculated as OR_{during-pandemic} divided by OR_pre-pandemic.
The ratio of odds ratios was calculated for one unit increase in body mass index (1 kg/m²).
Numbers in bold indicate a significant difference (p <0.05).