Table 2. National trends of the prevalence of asthma and β-coefficients of odds ratios before and during the COVID-19 pandemic in Koreans, weighted % (95% CI), in the data obtained from the KNHANES

Year	Pre-pandemic					During the pandemic		Trends in the pre-pandemic era, β(95% CI)	Trends in the pandemic era, β(95% CI)	βdiff between 1998-2019 and 2019-2021 (95% CI)	P-value for βdiff
	1998-2005	2007-2009	2010-2012	2013-2015	2016-2019	2020	2021
Overall	1.61 (1.50 to 1.73)	3.12 (2.85 to 3.39)	3.50 (3.17 to 3.83)	3.13 (2.84 to 3.42)	2.92 (2.68 to 3.16)	2.83 (2.34 to 3.32)	2.97 (2.44 to 3.50)	0.200 (0.127 to 0.272)	0.028 (-0.254 to 0.310)	-0.17 (-0.46 to 0.12)	0.248
Sex
Male	1.59 (1.43 to 1.75)	2.99 (2.65 to 3.33)	3.62 (3.15 to 4.08)	2.85 (2.45 to 3.24)	2.85 (2.51 to 3.19)	3.02 (2.30 to 3.74)	2.62 (1.91 to 3.32)	0.174 (0.074 to 0.273)	-0.117 (-0.504 to 0.269)	-0.29 (-0.69 to 0.11)	0.153
Female	1.64 (1.49 to 1.79)	3.24 (2.86 to 3.62)	3.39 (2.96 to 3.81)	3.40 (3.02 to 3.78)	2.99 (2.68 to 3.30)	2.63 (2.00 to 3.27)	3.33 (2.60 to 4.07)	0.225 (0.130 to 0.320)	0.173 (-0.221 to 0.568)	-0.05 (-0.46 to 0.35)	0.802
Region of residence
Urban	1.47 (1.35 to 1.59)	3.04 (2.73 to 3.34)	3.66 (3.28 to 4.05)	3.04 (2.73 to 3.36)	2.80 (2.55 to 3.06)	2.75 (2.20 to 3.31)	2.98 (2.38 to 3.58)	0.195 (0.118 to 0.273)	0.088 (-0.227 to 0.402)	-0.11 (-0.43 to 0.22)	0.515
Rural	2.29 (1.98 to 2.59)	3.45 (2.89 to 4.01)	2.84 (2.26 to 3.41)	3.53 (2.85 to 4.20)	3.56 (2.82 to 4.30)	3.25 (2.24 to 4.26)	2.94 (1.95 to 3.93)	0.236 (0.044 to 0.429)	-0.309 (-0.921 to 0.303)	-0.55 (-1.19 to 0.10)	0.096
Education
High school or lower education	1.93 (1.78 to 2.07)	3.27 (2.93 to 3.61)	3.60 (3.16 to 4.04)	3.51 (3.11 to 3.92)	3.15 (2.82 to 3.49)	3.63 (2.86 to 4.40)	3.27 (2.57 to 3.98)	0.255 (0.162 to 0.348)	0.062 (-0.315 to 0.440)	-0.19 (-0.58 to 0.20)	0.331
College or higher education	0.86 (0.70 to 1.02)	1.96 (1.55 to 2.37)	2.49 (2.00 to 2.98)	2.72 (2.22 to 3.22)	3.02 (2.59 to 3.45)	2.72 (1.87 to 3.57)	3.25 (2.36 to 4.14)	0.462 (0.334 to 0.590)	0.120 (-0.365 to 0.606)	-0.34 (-0.84 to 0.16)	0.182
Income
Income (lowest-second quartile)	2.23 (2.04 to 2.43)	3.75 (3.33 to 4.18)	3.91 (3.45 to 4.38)	3.30 (2.86 to 3.75)	3.47 (3.08 to 3.86)	3.66 (2.87 to 4.44)	3.48 (2.78 to 4.18)	0.162 (0.049 to 0.275)	0.007 (-0.389 to 0.404)	-0.15 (-0.57 to 0.26)	0.461
Income (third-highest quartile)	1.10 (0.98 to 1.23)	2.69 (2.35 to 3.03)	3.18 (2.73 to 3.64)	3.01 (2.62 to 3.40)	2.56 (2.25 to 2.86)	2.34 (1.77 to 2.91)	2.68 (1.99 to 3.37)	0.241 (0.148 to 0.335)	0.063 (-0.307 to 0.432)	-0.18 (-0.56 to 0.20)	0.358

Abbreviations: CI, confidence interval; KNHANES, Korea National Health and Nutrition Examination Survey.