Fatal car accidents in the United States spike by 6% during the workweek following the 鈥渟pring forward鈥� to daylight saving time, resulting in about 28 additional deaths each year, according to new University of Colorado Boulder research.听
罢丑别听, published today in the journal听Current Biology,听also found that the farther west a person lives in his or her time zone, the higher their risk of a deadly crash that week.
鈥淥ur study provides additional, rigorous evidence that the switch to daylight saving time in spring leads to negative health and safety impacts,鈥� said senior author C茅line Vetter, assistant professor of integrative physiology. 鈥淭hese effects on fatal traffic accidents are real, and these deaths can be prevented.鈥�
The findings come as numerous states are considering doing away with the switch entirely amid mounting research showing spikes in heart attacks, strokes, workplace injuries and other problems in the days following the time change.
Driving tired, in the dark
For the study 鈥� the largest听to date to assess the relationship between the time change and fatal motor vehicle accidents 鈥� the researchers analyzed 732,835 accidents recorded through the U.S. Fatality Analysis Reporting System from 1996 to 2017. They excluded Arizona and Indiana, where daylight saving听time was not consistently observed.
Our results support the theory that abolishing time changes completely would improve public health.鈥�
鈥揅eline Vetter
After controlling for factors like year, season and day of the week, they found a consistent rise in fatal accidents in the week following the spring time change. Notably, that spike moved in 2007, when the Energy Policy Act extended daylight saving time to begin on the second Sunday of March instead of the first Sunday in April.
鈥淧rior to 2007, we saw the risk increase in April, and when daylight saving time moved to March, so did the risk increase,鈥� said Vetter. 鈥淭hat gave us even more confidence that the risk increase we observe is indeed attributable to the daylight saving time switch, and not something else.鈥�
With the arrival March 9 of daylight saving time, clocks shift forward by one hour, and many people will miss out on sleep and drive to work in darkness鈥攂oth factors that can contribute to crashes.听
Those on the western edge of their time zone, in places like Amarillo, Texas, and St. George, Utah, already get less sleep on average than their counterparts in the east鈥攁bout 19 minutes less per day鈥攂ecause the sun rises and sets later but they still have to be at work when everyone else does.
鈥淭hey already tend to be more misaligned and sleep-deprived, and when you transition to daylight saving time it makes things worse,鈥� said first author Josef Fritz, a postdoctoral researcher in the department of integrative physiology. In such western regions, the spike in fatal accidents was more than 8%, the study found.
Daylight time or standard time?
The increase kicks in right away, on the Sunday when the clocks spring forward, and the bulk of the additional fatal accidents occur in the morning.
Changes in accident patterns also occur after the 鈥渇all back鈥� time change, the study showed, with a decline in morning accidents and a spike in the evening, when darkness comes sooner.听But because they balance each other out, there is no overall change in accidents during the 鈥渇all back鈥� week.
In all, over the听22 years of data analyzed, 627 people died in fatal car accidents associated with the spring shift to daylight saving听time.听
Because the data only include the most severe听accidents, the authors believe the results underestimate the true risk increase to drivers when time springs forward.
鈥淥ur results support the theory that abolishing time changes completely would improve public health,鈥� said Vetter. 鈥淏ut where do we head from here? Do we go to permanent standard time or permanent daylight saving time?鈥�
Research has shown it鈥檚 better for sleep听and overall health to have more morning light and less evening light. Under permanent daylight saving time, mornings would stay dark later in winter all over the country, with the western parts of each time zone seeing the sun the latest, Vetter noted.
鈥淎s a circadian biologist, my clear preference is toward standard time.鈥�
