Reentrainment of the circadian pacemaker during jet lag: East-west asymmetry and the effects of north-south travel

• Published in: Journal of theoretical biology Vol. 437; pp. 261 - 285
• Main Authors: Diekman, Casey O., Bose, Amitabha
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 21-01-2018
• Subjects: Algorithms; Biological rhythms; Circadian Clocks - physiology; Circadian oscillator; Circadian Rhythm - physiology; Computer Simulation; Entrainment; Humans; Jet Lag Syndrome - physiopathology; Light-dark cycles; Models, Theoretical; Photoperiod; Poincaré map; Sleep - physiology; Sleep Wake Disorders - physiopathology; Translatitudinal travel; Travel; Biological rhythms; Entrainment; Translatitudinal travel; Poincaré map; Light-dark cycles; Circadian oscillator
• ISSN: 0022-5193; 1095-8541
• DOI: 10.1016/j.jtbi.2017.10.002

•We use a mathematical model of the human circadian clock to study jet lag.•Jet lag severity depends on the traveler’s internal clock and the season of the year.•Our analysis explains when eastward travel is worse than westward and vice versa.•We predict north-south travel can cause jet lag even when no time zones are crossed.•Methods can be used by travelers visiting multiple destinations to minimize jet lag.
The normal alignment of circadian rhythms with the 24-h light-dark cycle is disrupted after rapid travel between home and destination time zones, leading to sleep problems, indigestion, and other symptoms collectively known as jet lag. Using mathematical and computational analysis, we study the process of reentrainment to the light-dark cycle of the destination time zone in a model of the human circadian pacemaker. We calculate the reentrainment time for travel between any two points on the globe at any time of the day and year. We construct one-dimensional entrainment maps to explain several properties of jet lag, such as why most people experience worse jet lag after traveling east than west. We show that this east-west asymmetry depends on the endogenous period of the traveler’s circadian clock as well as daylength. Thus the critical factor is not simply whether the endogenous period is greater than or less than 24 h as is commonly assumed. We show that the unstable fixed point of an entrainment map determines whether a traveler reentrains through phase advances or phase delays, providing an understanding of the threshold that separates orthodromic and antidromic modes of reentrainment. Contrary to the conventional wisdom that jet lag only occurs after east-west travel across multiple time zones, we predict that the change in daylength encountered during north-south travel can cause jet lag even when no time zones are crossed. Our techniques could be used to provide advice to travelers on how to minimize jet lag on trips involving multiple destinations and a combination of transmeridian and translatitudinal travel.