Dim nighttime illumination accelerates adjustment to timezone travel in an animal model.

Jetlag reflects a mismatch between local and circadian time following rapid timezone travel [1]. Appropriately timed bright light can shift human circadian rhythms but recovery is slow (e.g., 1-2 days per timezone). Most symptoms subside after resynchronization, but chronic jetlag may have enduring negative effects [2], including even accelerated mortality in mice [3]. Melatonin, prescription drugs, and/or exercise may help shift the clock but, like bright light, require complex schedules of application [1]. Thus, there is a need for more efficient and practical treatments for addressing jetlag. In contrast to bright daytime lighting, nighttime conditions have received scant attention. By incorporating more naturalistic nighttime lighting comparable in intensity to dim moonlight, we demonstrate that recovery after simulated jetlag is accelerated when nights are dimly lit rather than completely dark.