Sleep More, Live More Blog

“Most people think nothing of losing an hour of sleep for a single night,” says Somnee Co-Founder Dr. Matt Walker. The truth: “It is anything but.” For ~⅓ of countries worldwide, including the 48 states that ‘Spring Forward’ an hour every March, the transition to daylight saving time (DST) is often seen as a temporary annoyance that ultimately brings a welcome boost to daylight hours, later sunsets, and longer evenings. So you might be surprised to learn the clock change comes with a surprising price tag... “Should you tabulate millions of daily hospital records, as researchers have done,” says Dr. Walker, “you discover that this seemingly trivial sleep reduction comes with a frightening spike in heart attacks the following day.” The study Dr. Walker is referencing — which canvassed 42,000 hospital visits over 3 years — linked the jump to daylight savings with a 24% rise in heart attacks the next few days. (The good news: heart attacks dropped ~21% in November when the clocks fell back and we regained an hour of sleep.)1 That’s not even considering the impact on other aspects of health, mental health, work, and even traffic fatalities… Here, we’ll dig into how DST started in the US, global trends, and what researchers are saying in 2026 about the pros and cons of daylight savings for our health. Where did daylight savings in the US come from? What you’ve probably heard: it was introduced to give farmers more hours of sunlight. But according to University of Colorado sleep researcher Kenneth Wright, it was first introduced in Germany during World War I to save energy. The United States followed suit in 1918 as a wartime measure, repealing it after the war. The US reinstated it in 1942 for World War II, after which it evolved into a free-for-all, with states and localities switching back and forth at will. In 1966, Congress finally put an end to the Wild West of clock chaos, formalizing a permanent nationwide daylight saving spring forward/fall back calendar — except for Hawaii and Arizona, which opted for permanent standard time.2 How about the rest of the world and daylight savings? The United States isn’t the only country debating DST. The last ~50 years, countries worldwide have experimented with different approaches. But as of 2026, the global trend points towards permanent standard time. Over the past few decades, the PEW Research Center reports DST use dropped from ~½ of the world down to ~⅓. Most countries still using DST reside in Europe and the Americas.3 Some countries have experimented with permanent daylight savings: 4 The UK tried in 1968, repealing it 3 years later in 1971 Portugal attempted in 1992, cutting it 4 years later in 1996 Russia tried permanent DST in 2011, repealing it 3 years later and replacing it with permanent standard time Today, only 4 countries use year-round, summer-aligned schedules (like DST): Jordan, Syria, Turkey, and Paraguay. You might be wondering, “why have so many countries moved away from DST?” Let’s dig in. Option 1: Our current Spring Forward / Fall Back system A 2025 study by Stanford Medicine researchers suggests the worst choice for our circadian rhythms and health? Our current one: switching back and forth each year.5 “We found that staying in standard time or staying in daylight saving time is definitely better than switching twice a year,” shared senior author and professor of psychiatry and behavioral sciences Jamie Zeitzer, PhD.5 His is not the first study to find significant costs linked with our regular shift to DST in March: A 2020 study in Current Biology found a 6% increase in deadly motor vehicle accidents the workweek following springtime change6 A 2018 study in Accident Analysis & Prevention found road accidents jump 16% on the first day of DST and another 12% the second day after the clock change7 The biggest culprits: Darker mornings and sleep loss lead to longer morning grogginess, plus reduced visibility on still unthawed, icy roads. Option 2: Permanent Standard Time Researchers say this is the best move. When comparing the cost of less light in the evening (standard time) vs. less early-morning light (DST), “You generally need more morning light and less evening light to keep well synchronized to a 24-hour day,” said Zeitzer. “The more light exposure you get at the wrong times, the weaker the circadian clock,” Zeitzer added. All of these things that are downstream — for example, your immune system, your energy — don’t match up quite as well.” Their study found permanent standard time, which prioritizes morning light, would lower nationwide obesity by a whopping ~2.6 million people and strokes by ~300,000 cases annually.5 The reason: It lines up more with the natural rise and fall of the sun, allowing our circadian rhythms and energy to flow more optimally through the day. Proponents for permanent standard time include: American Academy of Sleep Medicine National Sleep Foundation Sleep Research Society Society for Research on Biological Rhythms The California Medical Association Option 3: Permanent Daylight Savings Time The biggest proponents for permanent daylight savings? Golf courses and open-air malls, reports Zeitzer.5 Their argument: More evening light equals more leisure time after work, less crime, and more energy savings. Here’s the kicker: The United States already tried a ‘permanent’ DST in 1974. Nixon signed it into law January 1, to run for two years. It was repealed by the fall, just 8 months later. Not only did it fail to provide meaningful energy savings — reports came to light of eight children in Florida being killed in traffic accidents as they walked to school in the early morning dark.8 This led newscasters to dub it “Daylight Disaster Time,” with approval ratings dropping from 79% to 42% in just 3 months.8 Other arguments against a permanent DST: Icier roads, sleepier commuters = more traffic accidents More difficulty falling asleep, with delayed sunsets pushing circadian rhythms later while bedtimes stay the same Children will need to fight harder against their natural, later-synched circadian rhythms, often heading to school while it’s still dark According to Wright, “If you look at the expert consensus from the scientific societies that focus on sleep, health and circadian rhythms, all of them agree this is a bad idea.” He adds, “Yes, we should be getting rid of the time change. But the science suggests we should be sticking with standard time, not daylight saving time.” Still, the Stanford study found that, while less beneficial for us than permanent standard time, permanent DST would decrease nationwide obesity by ~1.7 million and stroke by ~220,000 cases each year.5 Our Top Tip to Protect Your Sleep from Daylight Savings ⤵ Until we decide one way or the other, we’re stuck in the tug-o-war of Spring Forward / Fall Back. The best thing you can do for yourself? Start shifting your sleep/wake schedule 15-20 minutes earlier in the 2-3 days before daylight savings begins (Sunday March 8th, 2026). Explore our 7 top tips to safeguard your sleep this Sunday →

Sleep More, Live More Blog

Discover tips for better sleep, the latest in sleep science, and insights from experts including Dr. Matt Walker and Dr. Robert Knight.

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