Table 2. Adjusted OR of 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
	Adjusted OR (95% CI)	p-value	Adjusted OR (95% CI)	p-value
Grade
7th–9th grade (middle school)	1.000 (reference)		1.000 (reference)
10th–12th grade (high school)	2.837 (2.678 to 3.006)	<0.001	2.420 (2.269 to 2.582)	<0.001	0.853 (0.782 to 0.930)	<0.001
Sex
Male	1.163 (1.099 to 1.230)	<0.001	1.277 (1.197 to 1.363)	<0.001	1.098 (1.008 to 1.197)	0.033
Female	1.000 (reference)		1.000 (reference)
BMI*, kg/m2	1.018 (1.010 to 1.025)	<0.001	1.022 (1.014 to 1.031)	<0.001	1.004 (0.993 to 1.015)	0.489
Residence
Rural	1.000 (reference)		1.000 (reference)
Urban	1.183 (1.121 to 1.248)	<0.001	1.179 (1.108 to 1.254)	<0.001	0.997 (0.918 to 1.082)	0.935
Current smoking	13.101 (12.084 to 14.205)	<0.001	13.984 (12.705 to 15.392)	<0.001	1.067 (0.942 to 1.210)	0.308
Depression	1.862 (1.761 to 1.970)	<0.001	1.816 (1.703 to 1.937)	<0.001	0.975 (0.895 to 1.062)	0.566
Highest educational level of parents
College or higher	1.000 (reference)		1.000 (reference)
High school or lower	1.382 (1.285 to 1.485)	<0.001	1.543 (1.426 to 1.670)	<0.001	1.116 (1.003 to 1.243)	0.044
Unknown	1.035 (0.972 to 1.102)	0.288	1.142 (1.062 to 1.228)	<0.001	1.103 (1.002 to 1.215)	0.045
Economic level
High	1.000 (reference)		1.000 (reference)
Middle-high	0.810 (0.736 to 0.893)	<0.001	0.934 (0.833 to 1.048)	0.248	1.153 (0.992 to 1.340)	0.063
Middle	0.753 (0.686 to 0.826)	<0.001	0.902 (0.808 to 1.007)	0.068	1.198 (1.037 to 1.383)	0.014
Middle low	0.822 (0.734 to 0.921)	0.001	1.050 (0.917 to 1.203)	0.479	1.277 (1.070 to 1.525)	0.007
Low	0.929 (0.779 to 1.107)	0.409	1.246 (1.017 to 1.526)	0.034	1.341 (1.026 to 1.754)	0.032
School performance
High	1.000 (reference)		1.000 (reference)
Middle-high	0.982 (0.889 to 1.084)	0.717	1.105 (0.981 to 1.245)	0.099	1.125 (0.964 to 1.314)	0.136
Middle	1.068 (0.970 to 1.176)	0.180	1.109 (0.988 to 1.245)	0.080	1.038 (0.893 to 1.207)	0.624
Middle-low	1.229 (1.113 to 1.357)	<0.001	1.257 (1.116 to 1.416)	<0.001	1.023 (0.876 to 1.194)	0.776
Low	1.426 (1.274 to 1.597)	<0.001	1.412 (1.236 to 1.613)	<0.001	0.990 (0.832 to 1.179)	0.912

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).