While its origin is often debated, daylight saving time has been practiced for decades in the U.S. with the aim of allowing Americans to better use natural daylight.
But ditching the current practice of setting clocks forward an hour in the spring and back in the fall could be better for our health, Stanford Medicine researchers said Tuesday.
Getting rid of daylight saving time and permanently sticking to standard time could prevent 300,000 strokes a year and slash the number of Americans living with obesity by 2.6 million, researchers say.
The findings could help the U.S. fight often deadly medical conditions that impact hundreds of thousands of people. Stroke kills more than 165,000 Americans each year and obesity is linked to one in five deaths.
“We found that staying in standard time or staying in daylight saving time is definitely better than switching twice a year,” Dr. Jamie Zeitzer, a professor at the school, said in a statement.
Seasonal “waffling” disrupts the body’s natural clock. The circadian rhythm works to regulate hormones, the sleep-wake cycle, and digestion.
Disruptions to the cycle can lead to memory loss, fatigue, and even a delay in healing wounds, according to the Cleveland Clinic. Losing an hour of sleep, on the day daylight saving time begins in March, has previously been tied to more heart attacks and fatal traffic accidents. Sleep loss also increases the risk of stroke and obesity.
“The more light exposure you get at the wrong times, the weaker the circadian clock,” Zeitzer said.
Using county-level data, collected by the Centers for Disease Control and Prevention, the researchers also found that switching to daylight saving time permanently would only achieve about two-thirds as many benefits as choosing standard time. That would mean 1.7 million fewer Americans living with obesity and 220,000 fewer strokes.
However, they noted they did not account for weather and variation in human behavior in their analysis, which could affect their findings.
Americans will set the clocks back on the first Sunday in November.
Daylight saving time as it exists today began in 2007, but has been observed across much of the country since the mid-1960s.
Not all 50 states participate in the practice. Hawaii and Arizona do not observe daylight saving time.
Americans have been divided on its effectiveness for years, but President Donald Trump and members of Congress, on both sides of the aisle, recently lobbied to make daylight saving time permanent. Earlier this year, senators reintroduced bipartisan legislation to “lock the clock.” No action has been taken since then.
Supporters say committing to daylight saving time could save energy, deter crime and give people more leisure time after work. Proponents of standard time argue that more morning light is better for your health.
“And finally, we have data,” Zeitzer said.
