Figure 1. Melatonin and cortisol levels and expression profiles of peripheral clock genes in 15 subjects in blood samples collected every 4 h for a 24 h period.

Data of melatonin and cortisol are expressed as mean ± SD. Data of mRNA levels (means ± SD) are showed as % relative levels compared to the max value (acrophase) set to 100%. The shaded region represents sleep time. A statistically significant circadian rhythm was validated for both melatonin and cortisol levels and for expression of all clock genes with the exception of Clock gene with ANOVA repeated measures and Cosinor analysis (p < 0.05).