Table 2.

Results of the mixed-model analyses of variance for the primary outcomes (endogenous melatonin and frontal slow-wave activity (SWA) and secondary outcomes (subjective sleepiness and sustained attention performance). P-values adjusted using False discovery rates (FDR). Data presented as mean and 95% confidence intervals. Young group: n = 31 and older group: n = 16

	Young group			Older group			Group	Light condition	Group × light condition
Light condition	6500 K	3000 K	2500 K	6500 K	3000 K	2500 K	P-value*	P-value*	P-value*
Melatonin	26.6 (25, 28.3)	49.4 (47, 51.7)	48.3 (46.1, 50.5)	47.7 (44.5, 50.9)	49 (45.5, 52.2)	48.4 (45.2, 51.6)	<0.001	<0.001	<0.001
Sleepiness (KSS)	17.7 (16.7, 19)	31 (29.3, 32.7)	31.9 (30.2, 33.7)	37.7 (35.7, 39.7)	39.4 (37, 41.8)	39.1 (36.3, 41.8)	0.002	<0.001	0.004
PVT median RT	−15.2 (−21, -8.6)	−2 (−4.9, 1)	0.3 (-2.5, 3.3)	−1.6 (−4.2, 1.1)	2.2 (−0.1, 4.5)	2.4 (−9.2, 4.5)	0.01	0.006	0.002
PVT fastest RT	−15.3 (−22, -8.5)	−0.03 (−2.9, 2.9)	0.9 (−1, 2.8)	−1.2 (−3.3, 0.8)	−0.7 (−4, 2.5)	−0.2 (−3.9, 3.5)	0.01	0.002	0.007
PVT slowest RT	−4.2 (−7.9, 0.5)	−0.9 (−5.2, 3.4)	2.9 (-1.5, 7.3)	−6.1 (−14.2, 1.9)	5.6 (1.6, 9.6)	−3 (−11, 4.9)	0.8	0.02	0.1
All-night frontal SWA*	2 (2, 2.1)	2.2 (2.1, 2.2)	2.2 (2.1, 2.2)	1.9 (1.9, 2)	1.9 (1.8, 2)	1.9 (1.8, 2)	<0.001	0.006	0.07
Dynamics of frontal SWA**	2.3 (2.2, 2.3)	2.4 (2.3, 2.4)	2.3 (2.2, 2.4)	2 (1.9, 2.1)	2 (1.9, 2.1)	2 (1.8, 2.1)	<0.001	0.003	0.2

Melatonin levels, subjective sleepiness levels (Karolinska sleepiness scale, KSS) and psychomotor vigilance task (PVT) reaction time (RT) data expressed as percentage of baseline (see “Statistical analyses” for details on data normalization for each outcome measure)

*Slow-wave activity (SWA) data were log-transformed

**Mean and 95% confidence intervals for 1st non-rapid eye movement (NREM)—rapid eye movement (REM) sleep cycle. Mixed-model analyses of variance also included main effect “Sleep cycle”: p < 0.001, and the interaction of “Group” by “Light condition” by “Sleep cycle”: p = 0.005