No abstract

No abstract

Adenosine and functional A 1 adenosine receptor (A 1 AR) availability are supposed to mediate sleep-wake regulation and cognitive performance. We hypothesized that cerebral A 1 AR availability after an extended wake period decreases to a well-rested state after recovery sleep. [ 18 F]CPFPX positron emission tomography was used to quantify A 1 AR availability in 15 healthy male adults after 52 h of sleep deprivation and following 14 h of recovery sleep. Data were additionally compared with A 1 AR values after 8 h of baseline sleep from an earlier dataset. Polysomnography, cognitive performance, and sleepiness were monitored. Recovery from sleep deprivation was associated with a decrease in A 1 AR availability in several brain regions, ranging from 11% (insula) to 14% (striatum). A 1 AR availabilities after recovery did not differ from baseline sleep in the control group. The degree of performance impairment, sleepiness, and homeostatic sleep-pressure response to sleep deprivation correlated negatively with the decrease in A 1 AR availability. Sleep deprivation resulted in a higher A 1 AR availability in the human brain. The increase that was observed after 52 h of wakefulness was restored to control levels during a 14-h recovery sleep episode. Individuals with a large increase in A 1 AR availability were more resilient to sleep-loss effects than those with a subtle increase. This pattern implies that differences in endogenous adenosine and A 1 AR availability might be causal for individual responses to sleep loss.S leep loss is known to impair almost every aspect of cognition, such as learning (1), long-term memory consolidation (2), attention and psychomotor vigilance (PVT) (3), and executive functions (4), including decision making (5) and emotional control (6). Sleep deprivation further typically alters the frequency distribution of the waking electroencephalogram (EEG) as an indicator of alertness corresponding to cognitive performance (7). However, large interindividual differences exist in the degree of cognitive performance decline during sleep deprivation (3). In a trait-like process, some individuals keep high-level performance during sustained wakefulness, whereas others suffer from severe performance loss (3). The neuro-molecular mechanisms in the brain responsible for these different vulnerabilities are still largely unknown. Caffeine, commonly consumed for fighting fatigue, promotes wakefulness via adenosine receptor antagonism. It seems likely that the adenosinergic system is a neurochemical link between performance and sleep (8). Adenosine is contributing to the homeostatic process of sleep-wake regulation (for review, see refs. 9-12). As has been shown in cats and rats, extracellular adenosine concentration fluctuates rhythmically in many brain regions, such as the basal forebrain, increasing during wakefulness and decreasing during sleep: it thereby induces sleep after wake extension and is in turn restored to baseline levels after recovery sleep (13). For additional information on adenosine, see...

Summary European regulations restrict the duration of the maximum daily flight duty period for pilots as a function of the duty start time and the number of scheduled flights. However, late duty end times that may include long times awake are not specifically regulated. In this study, fatigue levels in pilots finishing their duty late at night (00:00–01:59 hour) were analysed and compared with pilots starting their duty early (05:00–06:59 hour). Fatigue levels of 40 commercial short‐haul pilots were studied during a total of 188 flight duty periods, of which 87 started early and 22 finished late. Pilots used a small handheld computer to maintain a duty and sleep log, and to indicate fatigue levels immediately after each flight. Sleep logs were checked with actigraphy. Pilots on late‐finishing flight duty periods were more fatigued at the end of their duty than pilots on early‐starting flight duty periods, despite the fact that preceding sleep duration was longer by 1.1 h. Linear mixed‐model regression identified time awake as a preeminent factor predicting fatigue. Workload had a minor effect. Pilots on late‐finishing flight duty periods were awake longer by an average of 5.5 h (6.6 versus 1.1 h) before commencing their duty than pilots who started early in the morning. Late‐finishing flights were associated with long times awake at a time when the circadian system stops promoting alertness, and an increased, previously underestimated fatigue risk. Based on these findings, flight duty limitations should consider not only duty start time, but also the time of the final landing.

No abstract