The U.S. Senate passed a bill last week that would make daylight saving time permanent. If it gains full congressional approval, the change would take place in fall 2023 and would keep evenings lighter year-round, eliminating the seasonal adjustments of springing forward and falling back to move in and out of standard time.
Many rejoiced. Others pointed out that a two-year shift to daylight saving time was attempted in the 1970s but quickly repealed.
The scientific consensus is that standard time — which most of the nation currently observes from November through March — is actually better for our health and circadian rhythms. Erik Herzog, PhD, a professor of biology and neuroscience at Washington University, told St. Louis on the Air that the effects of switching to daylight saving time are both immediate and long-lasting.
“The problems seem to persist for many days, especially if you think about things like traffic accidents and heart attacks,” Herzog said. “Those go up for about three days after the switch to daylight saving time.”
But, he added, it’s now just about the days after we spring forward. Standard time aligns more closely with our biology than daylight saving time.
“We as scientists and physicians have advocated that standard time, which is when a time zone has the sun directly overhead at noon, in the middle of the time zone — that’s the schedule that we should have our clocks on,” he said. “So that we, as biological entities living on this planet, are best aligned to the light-dark cycle.”
Not being aligned to that cycle can have significant health risks. Herzog said living in daylight saving time year-round would lead to an increase in obesity, heart attacks and cancer. He pointed to one study showing how just living on the western edges of time zones — an experience similar to daylight saving time — has had impacts on people’s health.
“We see an average of 10% increase in cancer rate for every 5 degrees west you travel. And then suddenly, as soon as you get to the next boundary, the next eastern edge of a time zone, the cancer rates drop again,” he said. “So this suggests that humans are doing their best to be aligned to the natural light cycle, and that those who have to wake up in the dark on the western edges of time zones are at risk for things like health risks, even lower sleep and lower economic earning potential.”
Herzog said waking up with the light is key to our health. During standard time, he said, our daily rhythms are all in the right order.
“Sort of like the ingredients going into a cake in the right order, and you end up with a good cake,” he said. “The idea is that during daylight saving time, we have a one-hour discrepancy between our body clock and the environmental clock. So we’re having a hard time waking up in the mornings, we’re more dependent upon our alarm clocks.”