Table 6.

Subjective sleepiness score predictions based on sleep condition and time-of-day effects in the final mixed-effects model.

	Sleepiness rating
Fixed-effect predictors	Estimates	CI	p
(Intercept)	5.81	5.47–6.16	<0.001
TSD condition at baseline (22:30)	−0.80	−1.27 to −0.33	<0.01
Session 1 (08:00)	−1.23	−1.63 to −0.83	<0.001
Session 2 (12:30)	−2.57	−2.97 to −2.17	<0.001
Session 3 (16:30)	−1.57	−1.97 to −1.17	<0.001
TSD	3.44	2.98–3.89	<0.001
TSD:Session 1 [TSD effect compared to session 3]	−0.74	−1.28 to −0.20	<0.01
TSD:Session 2 [TSD effect compared to session 3]	0.01	−0.53–0.55	0.97
Observations
Marginal R2	0.46

Note: CI, 95% confidence interval; TSD, total sleep deprivation; Marginal R² represents the variance explained by the fixed-effects predictors (Nakagawa et al., 2017). All rows representing categorical variables report the effect compared to a reference level. The reference level for session was the baseline session (22:30 h) therefore all other effect estimates for different levels of session compare to performance at 22:30 h. The reference level for TSD was the normal sleep group. For models including an interaction between TSD and session, the effect estimate for TSD refers to the effect of TSD on performance at Session 3. Interactions between TSD and session therefore refer to differences in the effect of TSD between the stated Sessions (i.e., 1 or 2) and Session 3.