Table 4. Regression Coefficients of the Sample and Sleep Period Main Effects in Models With Different Dependent Variables^a.

Dependent variable	Participants, No.	Lockdown vs control (sample main effect)				Sleep period on scheduled days
		β (SE)	Corrected P valueb	Uncorrected P valueb	R2β* (95% CI)c	β (SE)	Corrected P valueb	Uncorrected P valueb	R2β* (95% CI)c
HRQoL	7181	0.16 (0.25)	>.99	.51	0.000 (0.000-0.001)	1.28 (0.15)	<.001	<.001	0.027 (0.020-0.034)
Alcohol consumptiond	4519	−0.48 (0.08)	<.001	<.001	0.009 (0.005-0.016)	−0.02 (0.03)	>.99	.54	0.000 (0.000-0.001)
Caffeine consumptione	7214	−0.26 (0.09)	.04	.01	0.001 (0.000-0.004)	−0.32 (0.04)	<.001	<.001	0.013 (0.009-0.019)

Abbreviation: HRQoL, health-related quality of life.

^a In all models, age, primary language, and physical illness were also included as fixed effects and school was included as a random effect. The control sample included students who completed surveys from May to July 2017, and the lockdown sample included students who completed surveys from May to June 2020 during high school closure owing to the first COVID-19 wave in Switzerland.

^b P values were corrected for multiple comparisons using the Bonferroni method. Uncorrected P values were multiplied by 3.

^c Semipartial R² statistic.³²

^d Only students older than 16 years were included. Measured using a custom scale (eTable 1 in the Supplement) with scores ranging from 1 to 15; higher scores indicate greater alcohol consumption.

^e Measured using a custom scale (eTable 1 in the Supplement) with scores ranging from 1 to 20; higher scores indicate greater caffeine consumption.