The Cost of Permanent Daylight Saving Time: The Unhealthy Impact On Children

Ending the twice-yearly clock change sounds appealing. But keeping daylight saving time year-round would move winter sunrise an hour later, and a new University of Washington study suggests children would pay a substantial price: at least 2 billion additional trips to school before sunrise across the United States.

The researchers also found a troubling safety pattern. In their analysis of U.S. traffic records, fatal crashes involving school-aged pedestrians were roughly twice as likely during dark mornings as after sunrise. They published their findings on October 29 in Current Biology.

“It's called the ‘Sunshine Protection Act’ because you get an extra hour of light at the end of the day. But you will take that hour from the morning,” said senior author Horacio de la Iglesia, a University of Washington biology professor. “Nobody wants their kids to go to school in the dark.”

What the researchers counted

Nineteen states have approved measures supporting permanent daylight saving time, contingent on a change in federal law. To see what that change could mean for students, the research team examined 14 of those states. They used school enrollment, start times, and locations to estimate how many trips to school would happen before sunrise under permanent daylight saving time, then compared that figure with the current system.

The difference was striking. Washington state would see nearly 35 million additional dark school commutes. Georgia would see about 71 million—the largest increase among the states studied. Extrapolating to the whole country, the researchers estimated at least 2 billion additional trips to school in darkness.

That national figure may be low. For the projection, the team assumed students would leave for school around 8 a.m. Many leave earlier, especially those who attend before-school programs or eat breakfast at school.

“That's pretty late, so our calculation is likely an underestimation of the real number,” said lead author Guadalupe Rodríguez Ferrante, a postdoctoral researcher in biology at the University of Washington.

The effects would not be evenly spread. Communities near the western edges of time zones already see later sunrises, so places such as Forks, Washington, would be especially affected. Early school schedules would compound the problem. In Mississippi and Alabama, where schools start before 8 a.m. on average, the study estimated that dark school trips would rise from roughly 2 million per state under the current system to more than 20 million per state.

Morning light matters, too.

The concern isn't limited to traffic. Morning sunlight helps set the body's circadian clock, which influences sleep, mood, appetite, and other daily functions. A later sunrise could make that light harder for children to get, particularly when school schedules require them to be up and out early.

“When we send kids to school in the dark, we are depriving them from an opportunity to get that morning daylight,” Rodríguez Ferrante said.

How dark mornings can affect sleep and learning

Morning light is one of the strongest signals that tells the brain when a new day has begun. Light reaching the eyes helps reset the circadian clock, which coordinates daytime alertness and nighttime sleepiness. When sunrise comes later, children may get less of that signal before school—especially in winter, when they might spend much of the morning indoors.

That matters for a still-developing brain. If a child's body clock drifts later while school still starts at the same time, falling asleep early enough can become difficult. Too little sleep can make it harder to concentrate, remember new information, regulate emotions, and stay alert in class. Teenagers may be particularly vulnerable because their circadian rhythms naturally shift later during adolescence.

A dark commute does not, by itself, show that a child's brain has been harmed. The study counted trips before sunrise; it did not measure students’ sleep or brain function. Its findings do raise a practical question: if permanent daylight saving time makes morning light harder to get, how will children get the light and sleep they need?

Later school start times might seem like an answer, especially for teenagers, whose biological clocks tend to shift later. But the researchers argue that adjusting school schedules to recover morning daylight could push other parts of the day later as well.

Permanent daylight saving time offers a simple promise: more light after work and school, without changing the clocks each fall. The study asks policymakers to weigh that promise against what happens before the school day begins—when millions of children could be traveling in the dark.