Figure 1. Altered molecular circadian rhythms of salivary cortisol and relative PER1/ARNTL expression levels following bright light exposure before bedtime.

Twenty-five young, healthy male subjects were exposed to 150 lux artificial light at night (ALAN) before bedtime for 2 consecutive days. The circadian rhythms of salivary cortisol concentration (A) and relative PER1/ARNTL expression levels (B) are indicated as black circles connected with a continuous black line. After the 150 lux ALAN exposure, the same 25 subjects were exposed to 1,000 lux ALAN for 5 consecutive nights. The circadian rhythms of salivary cortisol concentration (A) and relative PER1/ARNTL expression levels (B) are indicated by white closed circles connected with a dashed black line. Data are expressed as mean ± standard error of the mean (SEM).