Figure 1

Time course of alertness, melatonin and cortisol profile and activity. Time course of the (a) Karolinska Sleepiness Scale (KSS), the (b) melatonin profile, the (c) cortisol profile and the (d) wrist activity in 26 young (left panel) and 12 older participants (right panel) under dim light (black lines), white light (red lines) or blue-enriched white light (blue lines). Data are plotted as a mean for each 2-hour bin for the KSS score, the melatonin and cortisol profile and in 3-hour bins for the wrist activity relative to elapsed time (hours) after wake-up. The error bars represent the standard error of the mean.