Table 4. Nationwide trends in average sleep time from Korean adults in Community Health Survey, 2009-2021.

Before the pandemic					During the pandemic	Sleep time trend, β (95% CI)		Trend difference, βdiff (95% CI)
	2009-2011	2012-2014	2015-2017	2018-2019	2020-2021	Before the pandemic	During the pandemic
Overall	6.710 (6.707 to 6.713)	6.628 (6.625 to 6.631)	6.556 (6.553 to 6.558)	6.628 (6.624 to 6.631)	6.773 (6.770 to 6.777)	-0.028 (-0.029 to-0.027)	0.023 (0.022 to 0.024)	0.051 (0.050 to 0.052)
Income
< 3 million won	6.685 (6.680 to 6.690)	6.599 (6.594 to 6.604)	6.539 (6.535 to 6.544)	6.592 (6.586 to 6.599)	6.649 (6.643 to 6.656)	-0.024 (-0.026 to-0.023)	0.007 (0.006 to 0.008)	0.031 (0.030 to 0.033)
≥ 3 million won	6.698 (6.693 to 6.703)	6.630 (6.626 to 6.635)	6.575 (6.571 to 6.579)	6.645 (6.640 to 6.650)	6.861 (6.856 to 6.866)	-0.020 (-0.022 to-0.018)	0.042 (0.040 to 0.043)	0.062 (0.059 to 0.064)
Unknown	6.756 (6.751 to 6.762)	6.690 (6.683 to 6.696)	6.504 (6.473 to 6.535)	6.658 (6.650 to 6.667)	6.822 (6.814 to 6.830)	-0.031 (-0.033 to-0.028)	0.027 (0.025 to 0.029)	0.058 (0.055 to 0.061)
Current smoking status
No	6.714 (6.710 to 6.717)	6.631 (6.627 to 6.634)	6.559 (6.556 to 6.563)	6.629 (6.625 to 6.633)	6.761 (6.757 to 6.765)	-0.028 (-0.029 to-0.027)	0.021 (0.020 to 0.021)	0.048 (0.047 to 0.050)
Yes	6.698 (6.692 to 6.704)	6.619 (6.612 to 6.625)	6.539 (6.532 to 6.546)	6.620 (6.611 to 6.629)	6.837 (6.828 to 6.846)	-0.030 (-0.033 to-0.028)	0.034 (0.032 to 0.036)	0.064 (0.061 to 0.068)
Alcohol consumption, days/month
0	6.714 (6.710 to 6.719)	6.621 (6.617 to 6.626)	6.535 (6.531 to 6.540)	6.605 (6.599 to 6.610)	6.690 (6.684 to 6.696)	-0.031 (-0.033 to-0.030)	0.012 (0.011 to 0.013)	0.043 (0.041 to 0.045)
1–4	6.731 (6.726 to 6.736)	6.658 (6.654 to 6.663)	6.594 (6.590 to 6.599)	6.672 (6.666 to 6.679)	6.851 (6.843 to 6.858)	-0.027 (-0.029 to-0.025)	0.032 (0.031 to 0.034)	0.059 (0.057 to 0.062)
5–30	6.671 (6.665 to 6.677)	6.600 (6.594 to 6.606)	6.544 (6.537 to 6.550)	6.618 (6.610 to 6.626)	6.850 (6.844 to 6.856)	-0.021 (-0.023 to-0.018)	0.040 (0.038 to 0.042)	0.061 (0.058 to 0.064)
BMI
Under and normal	6.754 (6.750 to 6.758)	6.671 (6.666 to 6.675)	6.598 (6.594 to 6.603)	6.682 (6.676 to 6.688)	6.821 (6.815 to 6.826)	-0.027 (-0.028 to-0.025)	0.021 (0.020 to 0.022)	0.048 (0.046 to 0.050)
Over and obese	6.661 (6.657 to 6.665)	6.584 (6.579 to 6.588)	6.515 (6.511 to 6.519)	6.587 (6.582 to 6.592)	6.735 (6.730 to 6.740)	-0.025 (-0.027 to-0.024)	0.024 (0.023 to 0.025)	0.049 (0.047 to 0.051)
Education background
≤High school	6.696 (6.692 to 6.700)	6.603 (6.599 to 6.607)	6.519 (6.515 to 6.523)	6.586 (6.581 to 6.591)	6.662 (6.657 to 6.667)	-0.032 (-0.033 to-0.031)	0.010 (0.009 to 0.011)	0.042 (0.041 to 0.044)
≥College	6.740 (6.735 to 6.744)	6.673 (6.669 to 6.678)	6.617 (6.612 to 6.621)	6.698 (6.692 to 6.703)	6.948 (6.943 to 6.953)	-0.022 (-0.024 to-0.019)	0.051 (0.049 to 0.052)	0.072 (0.070 to 0.075)
Occupational group
White-collar	6.629 (6.623 to 6.635)	6.575 (6.569 to 6.580)	6.527 (6.522 to 6.532)	6.603 (6.596 to 6.610)	6.874 (6.867 to 6.880)	-0.019 (-0.022 to-0.016)	0.066 (0.063 to 0.068)	0.085 (0.081 to 0.089)
Blue-collar	6.669 (6.665 to 6.673)	6.600 (6.596 to 6.604)	6.525 (6.520 to 6.529)	6.585 (6.579 to 6.590)	6.728 (6.722 to 6.733)	-0.030 (-0.032 to-0.029)	0.025 (0.023 to 0.026)	0.055 (0.053 to 0.057)
Unknown	6.793 (6.787 to 6.798)	6.693 (6.687 to 6.698)	6.610 (6.604 to 6.616)	6.690 (6.683 to 6.697)	6.771 (6.764 to 6.777)	-0.027 (-0.029 to-0.026)	0.010 (0.009 to 0.011)	0.037 (0.035 to 0.039)
Marital status,
Married	6.712 (6.708 to 6.715)	6.632 (6.628 to 6.635)	6.563 (6.560 to 6.567)	6.623 (6.619 to 6.628)	6.742 (6.738 to 6.746)	-0.031 (-0.032 to-0.030)	0.020 (0.019 to 0.021)	0.051 (0.049 to 0.053)
Single	6.706 (6.700 to 6.712)	6.618 (6.612 to 6.625)	6.537 (6.531 to 6.543)	6.637 (6.630 to 6.644)	6.835 (6.828 to 6.842)	-0.023 (-0.025 to-0.021)	0.026 (0.025 to 0.028)	0.049 (0.047 to 0.051)

Abbreviation: BMI, body mass index; CI, confidence interval; OR, odds ratio.
The bold numbers indicate a significant difference (p <0.05)