Simulation of jet lag following a trip with stopovers by intermittent schedule shifts

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Abstract
The time course of resynchronization of the circadian activity rhythm in hamsters was observed following a 10‐hr advance or delay in the light‐dark cycle (LD 12:12). Twenty‐six shift patterns of the lighting schedule were studied, which consisted of daily, 3‐step, 2‐step and 1‐step shifting. So long as the daily shift of the lighting schedule was 1 hr or less, the locomotor rhythm followed the shift perfectly. As the amount of daily shift increased, the time course of activity onset deviated more from the time of lights off. The tendency was more marked in advancing shifts. Responses of the rhythm to the stepwise shift were essentially the same, but it took more days before entrainment was achieved. Shift error and time constant estimates were given by fitting the time course of entrainment to an exponential model. The time constant became shorter with increasing amount of daily shift up to 2 hr per day, increasing number of shift steps, and/or reduced amount of the initial shift of the series. The shift error estimated was 0.51 ± 0.12 hr, indicating precise resynchronization. Hence, a quicker resynchronization will be expected when a multiple step shift with a moderate initial shift is employed. Graphical follow‐ups revealed that from a practical viewpoint a 2‐step shift (in a case of 10‐hr shift, for example, a shift of 3 hr followed by another 7 hr) was recommendable because of less inconvenience to travelers.

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