Spike in fatal car crashes in U.S. linked to time change
Sleep experts analyze daylight saving time
Clocks around Canada are springing forward on Sunday for daylight saving time, effectively robbing Canadians of an hour of sleep.
The practice of moving clocks ahead in the spring and pulling them back in the fall to conserve daylight hours has been around for more than a century, but scientists have long warned the change could pose negative health effects.
Now, a new study published in Current Biology says there’s a link between the spring DST transition and an increase in fatal car accidents in the U.S.
According to researchers, the rate of fatal car accidents in America increases by about six per cent the week after the clocks move forward an hour each year, which could be caused by the ensuing sleep deprivation and misalignment of drivers’ circadian sleep rhythms.
Céline Vetter, senior author of the study and director of the Circadian and Sleep Epidemiology Laboratory at the University of Colorado Boulder, said the team analyzed a database of fatal accidents in the U. S. between 1996 and 2017. In total, it looked at 732,835 cases and documented the date and time of each collision.
Vetter told the National Post that, broken down, it comes out to 28 deaths a year that could be attributed to the DST shift.
“It’s what you would consider a modest effect,” Vetter said. “What’s really important is it affects everybody. If you have a large portion of the population that is affected, then you would say even a small effect definitely has a public health impact.”
She added that the underlying causes for the increase, including disruption of sleep and light changes, should be transferable to Canada.
While there are other possible variables the team had to look at to determine whether DST was a factor in these accidents — such as changing weather patterns — there was one factor that proved the link between the time change.
In 2007, Canada and the U. S. extended the duration of daylight saving time by around four to five weeks. Before 2007, DST would start on the first Sunday in April and end on the last Sunday of October. But since then it begins on the second Sunday of March and ends on the first Sunday of November.
“If it’s really DST that leads to that increase in traffic accident risk,” Vetter said, “then we should see that before 2007, the peak in traffic accident risk in spring that has been reported before should move to that week.”
By analyzing the accident data, researchers found that the uptick in fatal car crashes did indeed move from April to March in 2007 when DST did, and they didn’t see any increases in April since.
“It’s hard when you use this large scale observational data, so it’s always really hard for us to say it’s really that thing,” Vetter said. “But this is a novel piece of evidence that further supports our observations.”
it affects everybody. ... even a small effect (has) a public health impact.
Vetter said the accident rate actually increases in the western time zones. Since the sun rises at a later time there than in the east, people required to wake up earlier for work or studies will be exposed to less morning sunlight, which will cause them to likely feel less awake — a term she calls “social jet lag.”
“Because DST is changing the timing of when you have to get to work — it doesn’t change when the sun comes up, it’s just a change of your clock — you get less morning light and more evening light,” Vetter said.
The study concludes by recommending DST be abolished and that countries such as Canada and the U. S. return to Standard Time, which is how the clocks currently operate between November and March.
Vetter said one of the most significant aspects of her team’s findings is that the 28 deaths a year could potentially be preventable if we made the switch, especially because she believes there’s no real reason to stay on daylight saving time.
Since 1966, Saskatchewan stopped switching their clocks over, and stays in perpetual daylight saving time, and the government of Yukon announced on Wednesday that it was going to stop the clock change and remain on DST as well.
But Vetter is advocating to stay specifically on Standard Time, worrying that on permanent DST, you would lack important morning light and get too much evening light, which would shift your sleep patterns to a later schedule.
“Translation always takes some time. I think every change is hard,” Vetter said. “I think now is a good time.”