Martin Vejvoda

Jet lag and sleepiness in aircrew.

SUMMARY  Jet‐lag and day‐time sleepiness cannot be avoided in transmeridian operations, because work hours of aircrews interfere with the circadian system through irregular work‐rest schedules and rapid time‐zone transitions. Although the primary cause of accidents is usually the human factor, jet lag and sleepiness have seldom been officially identified as causes of inadequate functioning in the cockpit. However, research clearly indicates that flights at night and/or across time zones will impair performance and reduce safety. Research on countermeasures have focused on on‐board napping, crew augmentation, behavioural strategies against jet‐lag, light treatment and melatonin administration. Regrettably, scientific knowledge has been successfully transmitted to only a very few national authorities responsible for work hours of aircrews.

CHRONOBIOTIC EFFECTS OF THE MELATONIN AGONIST LY 156735 FOLLOWING A SIMULATED 9H TIME SHIFT: RESULTS OF A PLACEBO-CONTROLLED TRIAL

Introduction: The melatonin agonist LY 156735 (LY) is a new investigational drug under development to treat circadian rhythm disorders. The present study assessed the efficacy of LY to alleviate the symptoms of shift lag and to enhance readaptation of desynchronized circadian rhythms to a new time zone. Subjects and methods: Eight healthy male volunteers of age 25–35 yr participated in three identical trials of 13d duration in a temporal isolation unit separated by washout intervals. A high dose (HD) of 5 mg and a low dose (LD) of 0.5 mg of LY and placebo (PL) were administered double-blinded in a three-period cross-over design. Each trial consisted of an adaptation period, a pre-shift period for baseline measurements, a simulated 9h phase-advance shift, and a post-shift period for follow-up. The time shift was performed at 23:00h of day 6 by advancing the laboratory time to 08:00h of day 7. Double-blind study medication was administered at 14:30h on day 6, and at 22:30h on days 7–10. Subjective ratings of jet lag, alertness, tenseness, and daytime fatigue were assessed using visual analog scales (VAS) and standardized questionnaires. The objective markers of readaptation included core body temperature, wrist actigraphy, cortisol and electrolyte excretion, and a battery of computerized performance tests. Results: HD but not LD enhanced the readaptation speed of all physiological rhythms investigated, as demonstrated by a significantly faster movement of acrophases towards the post-shift target time. HD (p=0.05) significantly blunted the post-shift deterioration of performance in those tests that were sensitive to shift lag. Parameters of subjective well-being were not significantly affected by either dose. Conclusion: This pilot study demonstrates the chronobiotic efficacy of LY when taken at a dose of 5 mg/d.

Performance impairment during four days partial sleep deprivation compared with the acute effects of alcohol and hypoxia

OBJECTIVE Subjects were exposed to cumulated partial sleep deprivation (psd), alcohol intake and hypoxia in a sequential design to examine the impact on neurobehavioral performance. METHODS Sixteen healthy male volunteers were enrolled in this study and were exposed in turn, after adaptation and baseline measurements, to one day of periods of hypoxia, one day of alcohol intake and one day for recovering (with 8h time in bed TIB). Subsequently the exposition of those conditions is that the subjects spent 5h night restriction daily for four consecutive days, followed by two recovery days. Performance was tested five (or six) times per day with reaction time task (SRT) and unstable tracking task (UTT). RESULTS The performance impairment showed to be cumulative in both tests over the four sleep deprivation days and differed significantly from baseline. Corresponding performance deficits under the influence of the stressors were for SRT: four days psd, 13% O(2) concentration and a blood alcohol concentration (BAC) of around 0.4-0.6 per thousand for UTT: four days psd, 13% O(2) concentration and a BAC of around 0.6 per thousand. One night of 8h sleep restored performance nearly to baseline level. CONCLUSIONS A sleeping time of 5h per night for four consecutive days impairs performance in such a way that traffic safety may be compromised.

Pilot workload during approaches: comparison of simulated standard and noise-abatement profiles.

INTRODUCTION A new noise-reduced landing approach was tested--a Segmented Continuous Descent Approach (SCDA)-with regard to the resulting workload on pilots. METHODS Workload of 40 pilots was measured using physiological (heart rate, blood pressure, blink frequency, saliva cortisol concentration) and psychological (fatigue, sleepiness, tension, and task load) parameters. Approaches were conducted in A320 and A330 full-flight simulators during night shift. SCDA was compared to the standard Low Drag Low Power (LDLP) procedure as reference. RESULTS Mean heart rate and blood pressure during the SCDA were not elevated, but were partly, even significantly, reduced (on average by 5 bpm and 4 mmHg from the flying captain). Cortisol levels did not change significantly with mean values of 0.9 to 1.2 ng ml(-1). Landing was the most demanding segment of both approaches as indicated by significant increases in heart rate and decreases in blink frequency. Subjective task load was low. DISCUSSION Both approach procedures caused a similar workload level. Interpreting the results, methodological limitations have to be considered, e.g., the artificial and controlled airspace situation in the flight simulator. Nevertheless, it can be concluded that under these ideal conditions, the SCDA is operable without a higher workload for pilots compared to the common LDLP.

Significance of time awake for predicting pilots' fatigue on short‐haul flights: implications for flight duty time regulations

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.