Fig. 2.

Effects of three days of a simulated day or night shift schedule on the temporal patterns of circulating cytokines measured under constant routine. Data are shown as group means and standard error. The gap in the line show where the 24-h constant routine protocol began/ended. Overall 24-h levels of TNF-α were reduced in the night shift condition relative to the day shift condition (top left). Additionally, IL-6 increased progressively with time awake in both conditions, but since wakefulness started 12 h later in the night shift condition, the temporal changes in IL-6 were shifted relative to the day shift condition and relative to the central circadian pacemaker (top middle). For reference, diamonds on the top of the IL-6 graph indicate the timing of the dim light melatonin onset, a marker of the timing of the central circadian pacemaker, in each condition (Skene et al., 2018).