Researchers in various studies have concluded that traffic accidents, heart attacks, and strokes occur in the days following our clock-changing ritual.
As most North Americans prepare to turn their clocks forward an hour in a couple weeks, the debate over whether that’s a good idea is gaining steam.
Part of the reasoning behind the calls for doing away with daylight saving time has to do with its health impacts, at least in the days following the time shift.
The Finnish government will actively push the European Union to do away with the time changes, the Scandinavian nation’s parliament decided last fall. Numerous online petitions are calling for the U.S. government to do the same.
“Stop the unnecessary flip flopping of time,” one petition states. “It’s an antiquated practice that only aggravates people.”
Another petition cites research noting the increase in traffic accidents and heart attacks in the days and weeks after the “spring forward” time change.
Those health impacts largely stem from the disruption, however minor, to people’s sleep cycle.
“We know that insufficient sleep can have serious consequences for our health and performance, including contributing to accidents, impaired work productivity and academic performance, reduced quality of life, poor health, and even death,” Natalie Dautovich, an environmental scholar at the National Sleep Foundation and psychology professor at Virginia Commonwealth University, told Healthline.
She added that it’s hard to nail down specific health impacts of daylight saving time due to the “lack of systematic reviews or controlled studies.”
A few studies, however, have found ties between the time shift and health impacts.
The researchers suspected increased stress from losing an hour of sleep precipitated the heart attacks, particularly in people already prone to them.
A 2016 study found an 8 percent jump in the incidence of strokes in the two days following the spring time change, particularly during the morning hours. They attributed the spike to previously known ties between strokes and disruptions of people’s circadian rhythms. Those over 65 were 20 percent more likely to have a stroke during those days.
A 2016 study found daylight saving time was responsible for more than 30 traffic fatalities. That was built on previous research that had also found jumps in traffic deaths, likely tied to people being — even just slightly — more tired after the small loss of sleep and disruption to their rhythms.
That’s only a tiny fraction of the 30,000 deaths on the U.S. roadways every day, but, critics of daylight saving time say, what’s the point?
The practice is archaic, they say. It was started in the United States during World War II as a way to save fuel by giving Americans more daylight in the evening, thereby reducing their need to use energy for lighting.
In the decades since, daylight saving time has been expanded, now lasting from the second Sunday in March to the first Sunday in November in the United States. (Guam, Hawaii, the Navajo Nation, and Puerto Rico do not observe it.)
But the health impacts aren’t all negative.
The 2015 study, for instance, found a 21 percent reduction in heart attacks on the Tuesday following when clocks “fall back” in November.
“Any negative effects are transitional effects that occur at the clock change and last a day or a few days. Some of these have opposite effects at the other clock change,” David Prerau, author of “Seize the Daylight: The Definitive Book on Daylight Saving Time,” told Healthline.
Prerau also pointed to health benefits of people remaining active later into the evening due to the increased hours of sunlight after the traditional workday.
“Healthy sleep is a critical part of a healthy lifestyle that also consists of adequate exercise,” added Dautovich. “Ideally, after a good night’s sleep we can spend some time outside in the morning to set our ‘body clocks.’ This, in turn, helps to regulate our sleep.”
Over the long run, proponents say, daylight saving time may cause some deaths in the immediate period following the time shift, but the quality-of-life improvements from evening daylight over the course of the spring and summer leads to net long-term health benefits.