SCN & Rapid Changes

Hear Ye Hear Ye as the old town crier used to say. The SCN or brain’s internal circadian rhythm clock does NOT react well to rapid changes in light and dark (outside of the sun’s regular rise and setting). Rapid changes produce circadian disruption problems that can cause sleep dysfunction, daytime sleepiness, an increase in accidents, suppressed immune system, and so on. Rapid changes may be seen in shift work, especially if the shifts change frequently, and in jet lag. The number of time zones that are crossed is the factor in jet lag. Estimates are that it can take one day for every time zone crossed for the SCN or brain’s internal circadian rhythm clock to catch up. E-W or W-E flights are more problematic than N-S or S-N flights. Going straight north or south might have no time changes at all. Going West to East  is more problematic because you lose an hour. Going East to West is still problematic but slightly less so but milder because you gain time, which seems to hit the SCN less dramatically.