WashU Expert: Brace yourself, it’s fall-back time again

Biologist Erik Herzog on the abrupt time changes that mark the beginning and end of daylight saving time

At 2 a.m. Sunday, Nov. 1, people around the world will adjust their clocks to 1 a.m., observing the end of daylight saving time by waking an hour later. Falling back is easier than springing forward, said Erik Herzog, PhD, an expert on circadian rhythms from Washington University in St. Louis. But in both cases, we’re jumping out of sync with the environmental light cycle.


The consequences are not trivial. Herzog, professor of biology in Arts & Sciences who studies biological clocks, said jamming our biological clocks into forward and reverse, as daylight saving time does, does, in fact, affect our health and performance.

“The spring advance of our wall clocks is particularly pernicious,” Herzog said. “It is associated with statistically higher rates of traffic accidents over the following three days, and heart attacks over the following two days.

“In effect, we have a form of jet lag, where the internal clock takes several days to adjust to a new schedule. But springing forward is, in many ways, more difficult than traveling across time zones because the local light cycle has not changed.”

The fall schedule change isn’t as rough on us, but when fall comes, spring and another round of circadian stress is not far behind.

“If this fall marked the end of daylight saving time forever, we would all sleep better,” Herzog said.