005), with a trend for the delay group to be more alert than the control group on N3 (P?=?0.06). There were no group effect or group????day interactions when the analyses were conducted on Pexidartinib price the first KSS and VAS of the night (Fig.?5c,d). Group effect and group????day interaction were not significant for mood evaluations. No significant group effect or group????day interaction were found for any of the five reaction-time parameters extracted from the PVT, although a significant day effect was found in all of them (F4,140?>?5.58; P?<?0.001). Averaged results during baseline daytime work (BL) and during the fourth night shift (N4) are shown in Table?2 for each of the three groups. Spectral power of wake EEG (5?C9?Hz) revealed no group effect or group????day interaction. A significant day effect was found (F4,140?=?9.05; P?<?0.001) as spectral power was higher on N1, during the first night shift, than on all other days. Significant correlations were observed between DLMO absolute phase shift and mean INK-128 subjective evaluations of alertness (VAS, r?=?0.47; P?<?0.01), sleepiness (KSS, r?=??0.39; P?<?0.05) and mood (r?=?0.57; P?<?0.001) over the last night shift (N4). When a larger phase shift occurred, subjects felt more alert, less sleepy and in a better mood, regardless of the direction of the shift (Fig.?6). Absolute phase shift was not correlated with objective measures of vigilance nor with any measure of daytime sleep quality. Similarly, no significant correlation was found with the proportion of the episode of melatonin production during daytime sleep or during night work, or with the clock time of final DLMO. Finally, none of the individual parameters (chronotype check details score, age, DLMO at baseline and habitual bedtime-DLMO phase angle) showed a significant correlation with sleep and vigilance quality at the end of the protocol. The small partial circadian adjustments observed in this study produced limited effects on daytime sleep quality during simulated night work. Sleep efficiency and total sleep time showed small effect sizes (<?0.14), confirming the absence of group differences on PSG variables. The only indication for improvement was the return to baseline SWA levels after the third night shift (D3) in the delay group (Fig.?4b). This observation suggests that partial circadian adjustment by phase delay may decrease the accumulation of sleep debt over consecutive night shifts. Previous studies that tested the effects of partial circadian adjustment on daytime sleep quality have yielded ambiguous results. In a PSG study of simulated night work, increased total sleep time and sleep efficiency have been reported, with a phase shift of about 6?h in the experimental group compared to 2.4?h in the control group (Dawson and Campbell, 1991). In a report using sleep diaries, daytime sleep duration after two night shifts was 2?h longer in an experimental group having a 3-h phase delay compared to a control group with <?1?h of phase shift (Lee et?al., 2006).