Effects of Circadian Chronotype on PVT Performance in a Chronically Sleep Deprived Condition

Morning and evening chronotypes have been used to classify individuals into categories that represent differences in endogenous circadian preferences and periods of peak performance. This study investigated the influence circadian chronotype has on psychomotor vigilance test (PVT) performance during a 45-day spaceflight analog sleep restriction experiment. Twenty healthy participants (ages 29-55; 11 males) were restricted to five hours of sleep during weekdays and eight hours of sleep on weekends. Every third day, participants completed five PVT sessions throughout the day. PVT data of interest were compared from the first and last mission day of each sleep condition. PVT measures analyzed were mean response time (RT), mean speed (1/RT), and mean lapses. Mean RTs were faster overall for evening chronotypes regardless of the mission day or sleep condition. Mean speed was faster and mean lapses were fewer for evening chronotypes. A mixed effects ANOVA determined that there was no significant three-way interaction between circadian chronotype, sleep condition, and mission day. There was a significant difference between performance on the first and the last mission day of a sleep condition. For all chronotypes, performance was poorer on the last mission day after having experienced many days of chronic sleep deprivation. These results suggest that circadian chronotype does not have a large effect on individual performance, but confirms that chronic sleep deprivation over time impairs cognitive performance