Daylight Savings Transition Presents More Health Risks Than Modern Benefits


In time for daylight savings time starting on March 10, sleep experts weigh in on the harms of the daylight savings transition, such as increased risks for cardiovascular events, car accidents, and mortality.

Credit: Unsplash

Credit: Unsplash

Muhammad Adeel Rishi, MD, from Indiana University School of Medicine, experiences the switch to daylight savings time like anyone else might—excessive sleepiness and perhaps grabbing an extra cup of coffee. Unfortunately, the symptoms don’t go away after the first day of the spring forward.

Daylight savings bring inevitable social jetlag—a phenomenon describing when the 3 internal clocks do not align—which is a similar feeling to when a traveler experiences grogginess when trying to adjust to a time zone difference.

The body has 3 clocks: the solar clock, the social clock, and the circadian clock. The solar clock is dependent on where the sun is on the horizon. The social clock is the physical, on-the-wall clock people use to tell time, controlled by federal law. Lastly, the circadian clock is the clock inside the body telling someone what times in the day to be more alert.

Daylight savings time was created so farmers could work on their crops in the early morning. However, for many people—including the said farmers—the switch to daylight savings time is not just a mere annoyance but unnecessary.

“When he asked the farmers, they’re like, ‘the cows don't wake up based on where my clock clicks…they wake up based on the sun and their natural rhythms,” Logan Schneider, MD, a sleep medicine specialist from Stanford Medicine and the American Academy of Neurology, told HCPLive. “So, you can understand how if we just arbitrarily shift the clock and say, ‘everything's an hour different now,’ your body wouldn’t know that until it starts to adapt to the new social schedule that you impose upon it.”

Some people might think losing an hour reduces energy and boosts the economy since they are less likely to use electricity from light, but Schneider pointed out these arguments need to be “truly vetted.” With all the artificial light, night and day, does losing an hour save any energy?

The government has repeatedly attempted to eliminate the switch from standard time to daylight savings time. In 1974 it finally happened—but with bad repercussions.

“It was a horrible failure,” Rishi told HCPLive.“America decided, during the OPEC oil crisis when the Arab countries put an oil embargo on America and its allies for supporting Israel, we decided we’ll do permanent daylight-saving time starting in January of 1974. And the plan was that we will do this for 18 months and go back to standard time in the fall of 75. However, it very quickly became very unpopular.”

The planned 18-month switch to daylight savings time only lasted 9 months. England also tried permanent daylight savings from 1968 to 1971, but like in the US, it failed.1

Despite permanent daylight savings time being unfavorable, the US Congress tried to pass legislation to make daylight savings permanent—again. The Senate passed the Sunshine Protection Act in March 2022, but the bill did not reach the US House.2

The American Academy of Sleep (ASM) advocated against the legislation of making daylight savings permanent, putting out a statement in favor of permanent standard time.3

Although people love to complain about daylight savings, science-backed evidence suggests why the switch from standard to daylight savings time is harmful—and why standard time aligns more with the body’s internal clock.

“[A] fall [back] just an hour may seem like an insignificant adjustment and actually is clearly very significant for the body because everything is very well orchestrated to happen at specific times,” Schneider said. “Like the surge [in] adrenaline, the surge in cortisol, the stress hormone, the release of very various hormones like thyroid stimulating hormone, the release of melatonin, all of these things are orchestrated, as well as many other cellular functions and bodily functions around this 24-hour clock that the body predicts to happen the same way each day.”

The circadian clock has a specific neural process. The suprachiasmatic nucleus, inside the hypothalamus brain region and sitting above the optic chiasma, has a cell of a bundle of neurons that receives inputs from the eye. The light input travels through melanopsin receptors, and they send a light signal to the super cosmetic nucleus serving as the “master clock”; this clock is what allows the body to know what time of day it is, Schneider explained.

From there, the body sends signals down through molecules of melatonin or other circadian-regulating hormones to every cell in the body, each of which has its own biological clock. When the body functions well, all the biological clocks align so all organs know when they get hungry, when they secrete insulin, and when they release inflammatory markers.

“It’s like having that central atomic clock in the world. All of our phones ping and say, ‘Hey, what time is it?’ This is what’s going on in the brain houses that master clock, it sends a signal out to say, ‘Hey, this is what time we’re getting from the sun.' And they’ll send their messages back and say, ‘Well, this is what the body is telling us to do so that we can adjust that schedule and fine-tune it centrally,”’ Schneider said. “And so basically, it’s that feedback back and forth between the master clock in the brain and the signals that it sends out to the body either through the neuronal systems that it does that go throughout the brain and other parts of the body or through these molecules that it causes to secrete like melatonin that helps the body.”

Schneider stressed the importance of receiving morning light as it helps set the biological clock.

“Our bodies depend upon that as a cue to wake up and set their biological clock for the day in anticipation of the next 24 hours or so, and so standard time ensures that that is closer aligned to when we typically would wake up instead of far delayed,” Schneider said.

Not only does the switch to daylight savings time disrupt the circadian clock, but the switch has harmful cardiovascular consequences.4

“If you're in an uncompensated or slightly compensated state of medical illness, that might be just enough to tip you over the edge and make your body have a problem,” Andrew Namen, MD, FCCP, FAASM, from the American Academy of Sleep and professor of pulmonary, critical care, allergy, and immunologic diseases at Wake Forest University told HCPLive. “That could mean increased inflammation and then you have a heart attack the next day, or various other things that come as a consequence of not getting enough sleep on a regular basis.”

Additionally, the switch to daylight savings increases people’s risk of stroke, atrial fibrillation, and hospital admissions. Rishi said some evidence suggests the risk of heart attack stays elevated throughout the 8 months of daylight-saving time.

“If that’s true, that’s obviously very concerning,” Rishi said.

Girardin Jean-Louis, PhD, from the Miami Miller School of Medicine, told HCPLive people at risk of a disease linked to circadian dysregulation have an increased risk for potential death due to the switch to daylight savings time. He also said the switch also sways mood regulation, impacting productivity.

Research suggests the switch can increase the risk of suicide ideation and attempted suicides.5 However, although evidence suggests a connection between mental health and the daylight savings switch, no randomized controlled trials have been done to prove causality as it is difficult to do ethically or economically.

A huge problem of daylight savings is the increase in traffic fatalities. A 2020 study found a 6% increase in fatal car crashes in the US following daylight savings time.6

This can be especially dangerous for children or teens walking to school. In places like Seattle, kids are walking to school in the dark.

“If you do the math, under permanent Daylight Savings Time, K through 12 kids will be walking school 4 months out of the school year, so pretty much half or more of the full school year, they will be walking to school in the night,” said Horacio de la Iglesia, a sleep expert at the Society for Research on Biological Rhythms and from the University of Washington. “Whereas if you were in permanent Standard Time, that time is reduced to 2 weeks only. So that’s a huge difference.”

De la Iglesia said something clinicians could advise their patients—especially those living in high latitudes—is light therapy lamps to produce more light in the winter. Other sleep experts provided advice clinicians could give their patients.

“I usually advise my patients to start changing the clock in their [room] by small increments about a week prior to the Spring Split so that their body is adjusted to the change prior to the change actually happening acutely,” Rishi said.

With the government tossing the idea around of eliminating the daylight savings switch, Schneider posed the core question: what should we do about the non-beneficial transition: should we keep with it or stick to either standard or daylight savings time?

“We all know exactly what it feels like to have social jetlag, and or actual jetlag, by at least an hour,” Schneider said. “And so, in that case, it’s very compelling and unambiguous that arbitrarily changing our clocks without a really compelling reason to do so, particularly since it imposes undesirable health consequences and makes you feel bad, [is not justifiable]. There…is no reason that I can think of that supports daylight saving transition.”


  1. Suni, E. Latest Updates: Daylight Savings Time in 2024. Sleep Foundation. January 22, 2024. Accessed March 4, 2024.
  2. Rishi MA, Cheng JY, Strang AR, et al. Permanent standard time is the optimal choice for health and safety: an American Academy of Sleep Medicine position statement. J Clin Sleep Med. 2024;20(1):121-125. doi:10.5664/jcsm.10898
  3. Martín-Olalla JM, Mira J. Sample size bias in the empirical assessment of the acute risks associated with daylight saving time transitions. Chronobiol Int. 2023;40(2):186-191. doi:10.1080/07420528.2022.2157738
  4. Reis DJ, Yen P, Tizenberg B, et al. Longitude-based time zone partitions and rates of suicide. J Affect Disord. 2023;339:933-942. doi:10.1016/j.jad.2023.07.080
  5. Fritz J, VoPham T, Wright KP Jr, Vetter C. A Chronobiological Evaluation of the Acute Effects of Daylight Saving Time on Traffic Accident Risk. Curr Biol. 2020;30(4):729-735.e2. doi:10.1016/j.cub.2019.12.045
  6. Why Do the Clocks Change? Royal Museums Greenwich.,disadvantages%20of%20British%20Summer%20Time. Accessed March 4, 2024.

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