Daylight saving time is one big experiment for scientists


To some people, the transition to daylight saving time means a few days of sleep deprivation, or the chance to leave work before the sky is completely dark. To others, it’s a perfect opportunity to conduct scientific research.

Not just sleep-related research. If you ever wondered whether changing the clocks twice a year would lead to more cyberloafing at work, you’ll be glad to know that business school professors wondered that too. Got a hunch that daylight saving time affects air quality? So did a geophysicist in Chile.

“Daylight saving time shifts can be looked upon as large-scale natural experiments,” researchers wrote in a 2012 study that examined whether lost sleep translated into a greater risk of heart attacks. (It did: Among Swedish adults, the the incidence of heart attacks was 4% higher than usual in the first week of daylight saving time.)


Here are some other discoveries made possible by springing forward and falling back:

Daylight saving time combats childhood obesity. The more daylight available in the evening hours, the more time kids spend getting some kind of exercise, according to a 2014 study in the International Journal of Behavioral Nutrition and Physical Activity. Researchers figured this out by putting fitness trackers on more than 23,000 kids and teens from nine countries. A 2012 study in the Journal of Physical Activity and Health found that British children got more exercise when there was more daylight between 5 and 8 p.m. “This strengthens the public health arguments for daylight saving measures,” the researchers concluded.

Daylight saving time can improve public safety. More natural light during the evening commute improves visibility for drivers, which translates into fewer crashes, according to a 2010 report in the Journal of Safety Research. On the flip side, many research groups have speculated that the sleep disturbances brought on by daylight saving time could lead to more workplace accidents. But studies in Canada and Finland found no change in the number of accidents after the clocks changed.

Good DNA won’t help you cope with daylight saving time. A 2014 study in the Annals of Human Biology examined whether people with particular variants of genes called CLOCK and PER3 adjusted more easily to losing an hour of sleep. They didn’t.

Daylight saving time can be stressful. People produced more of the hormone cortisol — which is released by the body in response to stress, among other triggers — when sunrise got pushed back. According to a 2014 study in the journal Chronobiology International, each one-hour delay was associated with a 5% median increase in cortisol in the bloodstream.

Springing forward really is more difficult than falling back. Italian researchers persuaded 14 college students to wear actigraphs in the weeks before and after the start and end of daylight saving time. The time change in the spring caused greater disruptions in the sleep/wake cycle, with students spending more time in bed and waking up more often during the night, among other things. These findings appeared in 2013 in Chronobiology International.

Changing the clocks can influence air quality. A study that examined the concentration of air pollutants hour by hour over 13 years found that the air was cleaner in the days after daylight saving time ended in the fall. These measurements, taken in Santiago, Chile, were reported in 2012 in the Journal of the Air & Waste Management Assn.


Springing forward prompts people to waste time on the Internet. When workers are tired due to lost or low-quality sleep, they are less likely to resist the temptation to goof off online, according to a 2012 study in the Journal of Applied Psychology. “The shift to Daylight Saving Time (DST) results in a dramatic increase in cyberloafing behavior at the national level,” the study authors concluded.

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