Sleepiness and Jet-Lag

Abstract

Jet-lag is an expression for a range of symptoms that include difficulty in initiating or maintaining sleep, day-time sleepiness decrements in subjective alertness and performance, gastronintestinal distress and psychosomatic manifestations. These symptoms are caused by long-haul flight operations associated with rapid multiple time-zone changes and night flying. Jet-lag is a consequence of the environmental and operational conditions, since the temporal relationship between the circadian timing system and the new local time is shifted. Due to the mismatch between the internal clock and external zeitgebers, and because of night flights and irregular duty hours, sleep cannot be taken at a time, when it is expected under normal circumstances. As a result, increased fatigue and sleepiness, acute and accumulative sleep loss, and performance decrements are observed in flight crews. Although it is difficult to identify the operational significance of the different factors on flight safety, statistics of accident rates for long-haul versus short-haul commercial flights in the last 25 years indicate that human error contributes to a relatively high number of accidents in long-haul operations. In recent years, much effort was undertaken by aviation research institutions to elucidate the complex interactions of work, environment and human factors and to examine potential countermeasures for alleviation of jet-lag and inflight sleepiness.