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A Wash U Professor Explains Why Daylight Saving Time Is Bad For Us

Gayle Harper/File photo
Daylight saving time for 2020 ends Sunday, which will make it seem like the sun is rising earlier.

This weekend, weary Halloween revelers across the U.S. will dutifully set their clocks to “fall back” — signaling the end of daylight saving time for 2020. The annual ritual may give some people an extra hour of sleep on Saturday night, but for others, including parents of young children and shift workers, it’s an annoying complication that takes days of adjustment.

And is it really necessary? A growing body of evidence suggests that our twice-yearly tradition of changing our clocks to gain or lose an hour of morning sunlight isn’t just irritating: It’s actually dangerous. In the first days after the switch to daylight saving time in the spring, heart attacks and traffic accidents both increase.

Several states are now contemplating an end to daylight saving time. Last year, the Illinois Senate actually passed a bill to abolish the practice, which dates back to World War I and was presented as an energy saver (research, it’s worth noting, is “decidedly mixed”).

On Thursday’s St. Louis on the Air, Erik Herzog explained why scientists increasingly believe we need to scrap the time shifting. A professor of biology and neuroscience at Washington University, he focuses on understanding circadian clocks and their role in behavior and health.

“What we experience is this shifting of the clock on the wall. Nothing in the world changes,” he said. “The only thing that's going to happen is we're going to ask everyone to somehow change their biology, which tells you when to wake up and when to go to sleep, to adjust to this social cue on the wall. And that’s a real challenge to our biology.”

While “falling back” has been associated with positive things (including a reduction in car crashes in the days after the shift), the price we pay is true havoc in the spring.

“When we spring forward, that loss of an hour of sleep is really challenging,” Herzog said. “We see things like three days of increased risk for car accidents, and three days of risk associations for heart attacks. … It’s one hour that cumulatively, over many days, can have a big impact on our health.”

Many callers shared Herzog’s assertion that the time changes aren’t worth it. But some argued that we should actually shift permanently to daylight saving time, giving up some light in the morning in exchange for increased evening sunlight. Sen. Marco Rubio is pushing a bill to do just that in Congress, and Herzog noted that the golf lobby (yes, there is a golf lobby) is a big fan.

But both the Society for Research on Biological Rhythms and the American Academy of Sleep Medicine say morning is when we really need the sunlight.

“Our circadian clocks depend upon light to help us synchronize to the local light-dark schedule,” Herzog said. “Having light in the morning helps us align our biology to local time. If we’re forcing ourselves to wake up before sunrise, that turns out to be against our biology.”

Herzog noted that when President Richard Nixon moved the U.S. to year-round daylight saving time in 1974, people hated it. It barely lasted a year.

“The popular demand was to get rid of it, and the practice was ended,” he said. “They returned within a year to the switching.”

St. Louis on the Air” brings you the stories of St. Louis and the people who live, work and create in our region. The show is hosted by Sarah Fenske and produced by Alex Heuer, Emily Woodbury, Evie Hemphill and Lara Hamdan. The audio engineer is Aaron Doerr.

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Sarah Fenske served as host of St. Louis on the Air from July 2019 until June 2022. Before that, she spent twenty years in newspapers, working as a reporter, columnist and editor in Cleveland, Houston, Phoenix, Los Angeles and St. Louis.