The pathophysiology of jet lag.

Jet Lag Disorder (JLD) is a recognized circadian rhythm sleep disorder characterized by insomnia or excessive daytime sleepiness (and sometimes general malaise and somatic symptoms) associated with transmeridian jet travel. It is a consequence of circadian misalignment that occurs after crossing time zones too rapidly for the circadian system to keep pace. The thesis of this review is that a rational treatment approach for jet lag can be grounded in an understanding of the biology of the human circadian timekeeping system. An overview of circadian rhythm physiology is presented with special emphasis on the role of light exposure and melatonin secretion in the regulation of circadian timing. Both timed light exposure (or avoidance) and exogenous melatonin administration have been recruited as treatment modalities to accelerate circadian realignment, based on an understanding of their role in circadian physiology. In addition to circadian misalignment, other contributing causes to jet lag are considered including travel-related sleep deprivation and fatigue. Clinical field trials that have tested the application of circadian rhythm based interventions are then reviewed.