Daylight saving time

Getting More Daylight Could Mean Better Sleep at Night

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Falling asleep later and waking up later this time of year? It could be you need to reset your sleep/wake clock. Going outside to get more daylight exposure – especially during the morning – might help, new evidence suggests. 

Yes, the use of electric lights and screens in the evening can mess with your sleep, but that’s not the whole picture, says Horacio de la Iglesia, PhD, a professor of biology at the University of Washington in Seattle. In fact, daylight is considerably brighter, even on an overcast day, compared to indoor lighting. So they’re not the same. 

In a study of 507 college students at the University of Washington, shorter daylight hours pushed sleep time about a half-hour later in the wintertime, compared to the other times of year. 

“It is important for a couple of reasons,” de la Iglesia says. 

First of all, teenagers and young adults tend to have very late sleep timing, “or a late chronotype as we call it, that is predictive of physical and mental health. Also, if you have a late chronotype, it probably means you struggle to get out of bed, you end up sleeping less, and you also increase what we call ‘social jet lag.’”

Social jet lag is the difference in sleep timing between the weekend and weekdays, “and that also is predictive of poor health,” de la Iglesia says. 

‘An Easy Fix’

Poor sleep can be costly in more than one way. Researchers in 2021 estimated that sleep disorders cost nearly $95 billion each year to diagnose and treat in the United States. 

“People are investing a lot of money in trying to develop drugs that improve your sleep, that lengthen your sleep, that advance your clock,” de la Iglesia says.  But a simple action like taking a brisk walk in the morning, for example, can help adjust your sleep clock, “and it will make you feel better. That’s what we like about it – that it’s an easy fix,” he says. “Even if you can get out for short amounts of time, that should help you advance your clock … and help you cope with the winter blues.” 

The study was in college students, but the findings could apply to people of other ages, de la Iglesia says. For example, younger teenagers also could gain from getting more daylight. 

“And older adults struggle with the winter here, with trying to get out of bed, and I think this should definitely translate to all ages.”

The students wore automatic data loggers around their wrists to measure activity and light exposure. Outdoor light was defined as at least 50 lux in intensity. The researchers compared findings from all four seasons, including the summer session at the university. 

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The study was published online in November in the Journal of Pineal Research. 

If it seems to make more sense that a later sunset in summertime would mean a later bedtime, you’re not alone.

“Although we had a good reason to think that sleep would change seasonally, we didn’t have any clear prediction on which direction it will change,” de la Iglesia says. “And in fact, the prediction that we had was completely wrong.”

Students fell asleep 35 minutes later and woke up 27 minutes later than students during the summer school days. 

The researchers did not find any significant differences in sleep duration by season. But students used an alarm to wake up about 10% more often in the fall and winter, compared to the spring and summer. 

Multiple Health Effects Possible

“My take is that sunlight exposure seems to have more effect than artificial light exposure – which goes along with what we know,” says Karin Johnson, MD, the medical director of the Baystate Regional Sleep Medicine Program in Springfield, MA, who was not involved with the study. 

“In addition to sleep loss, the misalignment of the social schedule with the body’s schedule on its own, even if average sleep duration is the same, affects health,” she says. “This effect helps explain why making daylight savings time permanent in the winter would likely be exponentially worse than how much it affects us in the summer.”

A later midpoint of sleep – defined as the halfway point in clock time between falling asleep and waking up – evening chronotype, and more social jet lag are “strongly associated with many health problems,” Johnson says. Metabolic syndrome and obesity, cardiovascular issues, depression, anxiety, and poorer performance and thinking skills are examples.

Latitude Adjustment

Going forward, de la Iglesia and colleagues would like to expand the study to other locations. 

They plan to work with collaborators in San Diego, which is at a lower latitude and does not have the same shifts in daylight. That could help answer the question of what happens on other school campuses where the shift in seasons is not as strong.

“Maybe this is an issue of northern latitudes,” de la Iglesia says.

Say We Abolished Daylight Saving Time. Here’s How it Would Change Sleep.

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It’s Saturday night on the second weekend in March. You’re enjoying your evening, winding down for the night, and tucking into bed. You wake up on Sunday at your usual time, just like the weekend before and the weekend after, without having to remember to change a single clock. That’s it.

Sounds too good to be true, right? Well, that’s just the start.

Daylight saving time (DST) begins for most of the United States at 2 a.m. March 13 this year, which got us thinking: What would a country without daylight saving time really look like? Would we sleep better?

According to sleep experts and other people who’ve thought about time-change sleep problems, abolishing daylight saving time might not just be about getting rid of minor annoyances. It could change how our bodies use, interpret, and adjust to light.

Without having to reset our clocks, we also could stop worrying about losing an hour of sleep, feeling tired after “springing forward,” or wondering what other effects the time change might bring. So maybe we stop wondering.

The End of ‘Spring Forward’ and ‘Fall Back’

Daylight saving time started in the early 1900s and has been mandated in the U.S. since 1967, with Arizona (except the Navajo Nation territory), Hawaii, and a number of U.S. territories not adopting it.

So we’re used to it. But we can envision what life would be like without it.

As of 2020, 63% of Americans support abolishing daylight saving time, according to an American Academy of Sleep Medicine1 (AASM) survey. In fact, 29 states2 have introduced bills to replace daylight saving time with one stable time, with 183 passing legislation stating they’d change, if they could. A U.S. House subcommittee just discussed the matter on March 9, as well.

60% of Americans support a National Permanent year-round time

What would happen first? We’d reduce schedule disruptions and having to remember which clocks auto-update. Without losing an hour of sleep on Sunday, you’ll probably wake up feeling more refreshed and less tired than you used to every March.

“That missing hour of sleep can have a major impact on your alertness, mood, performance, health, and safety,” says Kimberly A. Honn, assistant professor at Washington State University Spokane in the Sleep and Performance Research Center.

Without feeling the effects of sleep debt, you can get up Sunday morning ready to take on the world.

“[A] missing hour of sleep can have a major impact on your alertness, mood, performance, health, and safety.”

Kimberly A. Honn
Washington State University Spokane

The benefits don’t stop on Sunday, either. It’s typical to sleep 40 minutes less than usual4 on the Monday after the switch to daylight saving time, which a DST-free week might erase. It also would remove the need to establish a new sleep pattern after a clock change.

“It can take a week or longer for the biological clock to adjust to the new time,” says Honn, who adds that all the while, your “sleep debt stays with you.” During that time, you may face an increased risk of heart attack, stroke, and injuries in the workplace or on the road, studies say5.

When you go to work on Monday, you also might find an improvement in how much you can accomplish. Without sleep debt, you may have less brain fog and be more productive, as studies have shown6. Your co-workers may feel the same.

But work disruptions from clock changes occur for reasons other than just sleep loss. If daylight saving time were abolished nationwide, it would eliminate the inconsistencies in timing tied to the fact that not all states implement DST. Productivity may increase for a bit, at least offsetting the impact of workers who forget about the time change. Software developers may be freed from DST-related bugs in their code — “a big issue,” says Jay Pea, founder and president of the nonprofit Save Standard Time.

But what about in November, on the weekend when we usually “fall back” and gain an hour? While some people might miss having an hour added to their day in the fall, there would still be something to gain from keeping the clock steady. This is especially true for people who are already sleep-deprived7 or those who have pre-existing sleep disorders.

Stephanie Burton is an attorney in Kansas City who would prefer not to fall back. She has narcolepsy, a condition that affects sleep-wake regulation. She experiences a significant disruption when the clocks change in November.

“The best thing for narcolepsy is to maintain a sleep schedule,” says Burton, who adds that the switch throws off her sleep and concentration at work — and not just temporarily. “I would prefer consistency rather than months of unproductivity.”

Darkness is Good For Sleep, But So is Light

Removing a time change would mean a change to our daily exposure to natural light8, which directly influences our circadian rhythms and our sleep-wake cycles. Light itself is the most important external factor in getting good sleep.

If DST were abolished, it may be easier to get more exposure to natural light from March to November. If you think about it, this actually follows the natural course of the seasons.

Dec. 21, also known as the winter solstice, has the least amount of sunlight of any day of the year. Beginning on Dec. 22, each day starts getting a little bit longer. As we move farther into the new year, we get a steady uptick in morning light because the sun rises a few minutes earlier each day.

Without DST, we’d continue to benefit from this natural progress of longer days until the summer solstice on June 21. We’d have more opportunities to take in daylight in the early part of our day throughout the spring, even if just on the way to work or school.

The exact timing would vary by geographic location, but “people with standard work times would be able to wake up with the sunrise or after sunrise rather than having to wake up in darkness,” says Eva Winnebeck, a senior scientist and expert on sleep-wake rhythms at the Technical University of Munich and the Helmholtz Center Munich in Germany.

During the summer, we’d still get to enjoy the advantages of extra sunlight that go with longer days.

“We have a much longer daylight period in the summer,” which provides ample time for evening activities, Winnebeck says. “The worry that people have is that they miss out on evening daylight, but the sun is up for a long time anyway. It’s not a matter of daylight saving time.”

As summer winds down and fades into the fall, we would again follow the seasons and slowly experience less daylight. During that transition, our daily schedule would offer more morning light compared to what we had under DST.

Understanding How Our Bodies Adjust to Light

But what does the amount of daylight we get have to do with our sleep? Can’t we just turn on a lamp and get the light we need?

To answer these questions, we have to consider the three different clocks9 that mark our days:

  • The sun clock comes from planetary movement, which we observe based on the sun’s east-to-west path in the sky. By the sun clock, the midpoint of the day is when the sun is at its highest point overhead.
  • The body clock is how our brain and body coordinate and optimize biological functions in a day.
  • The social clock is the agreed-upon local time that we see on our watch or phone.

Our body clock has evolved and developed10 to follow signals from the sun clock, organizing processes in the body according to circadian rhythms.

Even on a cloudy day, natural light is many times stronger than artificial light8, so it is a crucial driver of our body clock.

Exposure to daylight helps keep the rhythms of our body clock in sync with our environment. This is crucial for good sleep and good health, as these rhythms can control our cells, muscles, and organs, says Sonia Ancoli-Israel, a University of California San Diego psychiatry and research professor.

Despite this, the body clock and its link to the sun clock often go unrecognized.

“Many people may not be aware of the important role circadian rhythms play in maintaining health,” says Kristen Knutson, associate professor of neurology at Northwestern University. “It’s not just a matter of heart health, kidney health, brain health, or any one system. It’s all of the above.”

“Many people may not be aware of the important role circadian rhythms play in maintaining health. It’s not just a matter of heart health, kidney health, brain health, or any one system. It’s all of the above.” Kristen Knutson, Northwestern University

Ideally, the social clock, which we use for everything from school times to work hours, would align with our body clock and the sun clock. But daylight saving time throws off that social clock.

“Under daylight saving time, your body is living in the wrong time zone,” says Elizabeth Klerman, professor of neurology at Massachusetts General Hospital and Harvard Medical School. This mismatch between the body clock and sun clock may detract from good sleep.

“When the exposure to sunlight in the morning is reduced, our biological clocks will drift later and later, making it harder to wake up,” Ancoli-Israel says. On top of that, additional evening light “pushes the biological clock to a later time and makes it more difficult to fall asleep.”

Even when delayed internal clocks from DST cause us to be awake later at night, we usually still have to report to work or get kids to school at the same time in the morning.

This erodes time for necessary rest: “Your alarm clock goes off in the morning, and you haven’t gotten enough sleep,” Klerman says.

We also may experience other health rewards11 from establishing a healthy circadian rhythm. Disrupted circadian rhythms can contribute to impaired thinking and immune function, as well as heightened risks of diabetes, depression, cardiovascular disease, and other medical conditions.

“Under daylight saving time, your body is living in the wrong time zone.” — Elizabeth Klerman, Massachusetts General Hospital and Harvard Medical School

While abolishing daylight saving time alone would not eliminate these problems, it could help.

“We have a society that is already sleep-deprived,” Winnebeck says. “Giving [us] daylight saving time worsens the whole problem.”

Finding the Right Time

Many Americans prefer doing away with twice-yearly time changes and instead having one fixed time year-round. So why was daylight saving time put in place at all?

Part of it was commerce, with some lobbying groups arguing that it led to more shopping and sports-watching. A leading initial rationale for daylight saving time was to reduce energy consumption by decreasing the need to have lights on in the evening. Still, changes in how we use electricity today may have reduced the energy savings from DST. About 6% of the money12 spent on electricity goes to lighting households after dark. In 2006, the Department of Energy called the energy savings “relatively small,” with the National Bureau of Economic Research finding that these were offset by added heating and cooling costs.

Daylight saving time itself has been enacted and repealed multiple times in the U.S. since 1918. After a patchwork of state and local time changes emerged in the mid-20th century, Congress passed the Uniform Time Act of 1966 to create a national policy that included DST.

But if the U.S. were to establish a stable, year-round time now, which permanent time is the right time? The jury is out on that one.

Arizona and Hawaii already use permanent standard time, as do Puerto Rico, Guam, and the U.S. Virgin Islands. Groups such as the National Sleep Foundation and the AASM13 have publicly supported a national policy to abolish daylight saving time.

More than a dozen states have passed legislation supporting permanent daylight saving time. Some people like the pattern of daylight that the spring-forward version of a day offers. They see DST as providing a better quality of life with more light in the evening when many people enjoy after-work and after-school activities.

Sleep experts who recommend abolishing daylight saving time in favor of permanent standard time recognize that no policy will make everyone happy. Clock changes remain a hotly contested political issue. Thus remains our current state: having it both ways.

How to Prepare For the Time Change

Despite support for abolishing clock changes, most of the U.S. will continue to spring forward and fall back for at least the next year. It’s essential to do what we can to prepare for the clock changes as we move from standard time to daylight saving time and vice versa.

Knutson advises people to try to get enough sleep in the nights before we spring forward so that we’re not already sleep-deprived going into the weekend. When the work week starts on Monday for many of us, we should remember that everyone is dealing with the disruptions of the clock change.

“People should have realistic expectations about their productivity and mood, as well as those around them,” Knutson says. “In other words, go easy on yourself and your friends, family, and colleagues.”

Especially if they forget to change the clocks.

How to Prepare for the Start and End of Daylight Saving Time

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Daylight saving time (DST) is a one-hour clock adjustment observed by most of the U.S. and Canada, as well as some other countries, that begins in March and ends in November. From November to March, those locations operate on standard time.

In the United States, switching between standard and daylight saving time occurs on specific weekends:

  • Spring Forward: Clocks are set ahead by one hour at 2 a.m. on the second Sunday in March.
  • Fall Back: Clocks are set back by one hour at 2 a.m. on the first Sunday in November.

Although the clock shifts only one hour at a time, this abrupt time change can cause meaningful sleep disruptions1. The shift to daylight saving time in March, in particular, can lead to reduced sleep quantity and quality2. The end of DST in November may not disrupt sleep as much, but some sleep-deprived people falsely assume the extra hour will reduce sleep debt3 when long-term sleep adjustments are usually needed instead.

Studies have found an association between the transition to daylight saving time and short-term risk of heart attacks, stroke, traffic accidents, emergency room visits, and serious mood disturbances4. A lack of sleep caused by the time change can affect thinking, decision-making, and productivity. Fewer negative health effects are associated with “falling back” in autumn, though studies have noted some abnormal changes such as an uptick in the use of psychoactive substances among men 20 and older.

These problems arise because the switch to and from daylight saving time alters your normal pattern of daylight exposure. This change can throw off your body’s circadian rhythm, the internal clock that helps control sleep and many other biological processes.

In short, the switch to daylight saving time shouldn’t be taken lightly. Developing a plan to cope with the time change can reduce its impact on your sleep and overall wellness.

Preparing for the Start of Daylight Saving Time

Because the switch to daylight saving time happens at a set time each year, you have the opportunity to prepare in advance, so that it’s less likely to harm your health.

Several practical steps can improve your sleep on the weekend of the time change and enhance your sleep habits over the long-term.

Gradually Adjust Your Schedule

You can get ready to “spring forward” in March by gradually shifting your schedule in the week leading up to the time change. The American Academy of Sleep Medicine advises trying to slowly adjust your schedule5 by going to bed around 15-20 minutes earlier each day.

The timing of other daily activities, such as meals and exercise, can also be gradually adjusted forward. By making these changes gradually over the week before the time change, you begin daylight saving time having already started to acclimate to the new time on the clock.

Sleep Well Beforehand

An important step in preparing for daylight saving time is obtaining quality sleep in the nights leading up to the time change. If you enter the daylight saving weekend already sleep deprived, it’s more likely you’ll have significant ill-effects6 in response to the time change.

In addition, receiving extra sleep beforehand can help you build up a “sleep bank” to better cope with the switch to daylight saving time. Studies have found that banking sleep before short periods of reduced sleep can decrease cognitive impairment7 and help preserve motor skills8.

Having built up a reserve of extra sleep may also reduce your sleep drive, making it easier to stay awake during the day and avoid involuntarily dozing off.

Consider Relaxation Techniques

At any time of year, relaxation methods, ranging from basic deep breathing to mindfulness meditation, can bring calm to your mind and body and make it easier to smoothly transition into sleep.

In the week before the shift to daylight saving time, you can apply these techniques as you gradually adjust your bedtime earlier. Relaxation methods may also come in handy if you find that you’ve woken up in the middle of the night.

Set Your Clocks Before Bed

Although the time change doesn’t officially occur until 2 a.m., set your watch and household clocks to the new time before you go to bed. This helps you hit the ground running and avoid any timing mishaps on Sunday.

Most cell phones and electronic devices automatically update to daylight saving time overnight. If your devices aren’t set to update the time automatically, make sure to adjust them before bed.

Prioritize Daylight Exposure

Light is the central driver of circadian rhythm, so finding time for daylight exposure on the days following the change to daylight saving time can help your body’s internal clock9 acclimate to the new timing of light and dark.

Natural light has the most powerful effect10 on our bodies’ circadian rhythm. Even on a cloudy day, natural light provides more of the illumination that works to align circadian rhythm than artificial indoor lighting does.

To decrease sleep disruptions after the switch to daylight saving time, make a plan to go outside, ideally in the morning, and receive sun exposure11 on the Sunday after the time change. If you live in a cold climate that makes being outside difficult, open your curtains and sit near a window to take in a meaningful dose of natural light.

Take Precautions in Case of Sleep Disruption

With the right preparation, you can reduce the chances that you’ll suffer sleeping problems because of the switch to daylight saving time. Nevertheless, it’s wise to try to take precautionary measures in case your sleep is affected.

Try not to overload your schedule on the Sunday or Monday after the time shift in case you’re experiencing daytime sleepiness. If possible, schedule important meetings or events for later in the week when you’ve had more time to adjust. It’s also best to avoid long drives right after the time change because of the potential dangers of drowsy driving.

Upgrade Your Sleep Hygiene

It’s much easier to receive consistent sleep if you have healthy habits and a bedroom environment that is conducive to sleep. These are known collectively as sleep hygiene, and upgrading your sleep hygiene can pay dividends during daylight saving time and throughout the year.

Although there are many components of healthy sleep hygiene, some important elements to consider include:

  • Related ReadingMaintaining a fixed sleep schedule on both weekdays and weekends
  • Keeping a stable routine to get ready for bed each night
  • Limiting or avoiding caffeine and alcohol, especially in the afternoon and evening
  • Going “device free” for at least 30 minutes before bed
  • Blocking out unwanted noise and light from your bedroom and/or using accessories like a sleep mask and ear plugs
  • Choosing a supportive mattress and comfortable bedding

Eat a Healthy Diet

Eating well is vital for overall health, and proper nutrition is tied to sleep as well. Although no single diet has been proven to be the best for sleep, balanced diets made up of lots of fruits and vegetables tend to provide the nutrients the body needs and have been associated with better sleep12.

Other ways to prevent food-related sleep disruptions include:

  • Eat dinner at least a few hours before going to bed
  • Limit consumption of heavy and spicy foods in the evening
  • Be mindful of caffeine in beverages, including sodas

Take a Short Nap if Necessary

If you find yourself grappling with significant daytime sleepiness in the days after switching to daylight saving time, a short nap may be beneficial. Keeping a nap under 30 minutes can boost your alertness while reducing grogginess after waking up.

Naps are best in the early afternoon when most people experience a dip in wakefulness. Avoid naps that are too late in the afternoon or evening because they can make it harder to fall asleep at night, exacerbating misalignment of your sleep schedule.

Preparing for the End of Daylight Saving Time

At 2 a.m. on the first Sunday in November, DST comes to an end and the time “falls back” by one hour. Since you gain an extra hour13 – rather than losing one – the end of DST is not associated with the same level of sleep disruptions as the beginning of DST in March. That said, the end of DST can still affect circadian rhythm and people may struggle to adjust their wake-up times14 for up to a week after falling back.

Many people feel refreshed and more alert thanks to this extra hour of sleep. However, those who are chronically sleep-deprived cannot erase their total sleep debt after one night. The end of DST can be an opportunity to improve your sleep habits and get an adequate amount of rest each night. According to the American Academy of Sleep Medicine, sleep-deprived individuals can best take advantage of the end of DST by:

  • Going to sleep at their usual bedtime on Saturday night before the fall back occurs
  • Waiting until bedtime to adjust their clocks
  • Setting their alarm for Sunday morning at the normal wake-up time

Daylight saving time linked to heart attacks, study shows.

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Switching over to daylight saving time, and losing one hour of sleep, raised the risk of having a heart attack the following Monday by 25 percent, compared to other Mondays during the year, according to a new U.S. study released on Saturday.

By contrast, heart attack risk fell 21 percent later in the year, on the Tuesday after the clock was returned to standard time, and people got an extra hour’s sleep.

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The not-so-subtle impact of moving the clock forward and backward was seen in a comparison of hospital admissions from a database of non-federal Michigan hospitals. It examined admissions before the start of daylight saving time and the Monday immediately after, for four consecutive years.

In general, heart attacks historically occur most often on Monday mornings, maybe due to the stress of starting a new work week and inherent changes in our sleep-wake cycle, said Dr. Amneet Sandhu, a cardiology fellow at the University of Colorado in Denver who led the study.

“With daylight saving time, all of this is compounded by one less hour of sleep,” said Sandhu, who presented his findings at the annual scientific sessions of the American College of Cardiology in Washington.

A link between lack of sleep and heart attacks has been seen in previous studies. But Sandhu said experts still don’t have a clear understanding of why people are so sensitive to sleep-wake cycles.

“Our study suggests that sudden, even small changes in sleep could have detrimental effects,” he said.

Sandhu examined about 42,000 hospital admissions in Michigan, and found that an average of 32 patients had heart attacks on any given Monday. But on the Monday immediately after springing the clock forward, there were an average of eight additional heart attacks, he said.

The overall number of heart attacks for the full week after daylight saving time didn’t change, just the number on that first Monday. The number then dropped off the other days of the week.

People who are already vulnerable to heart disease may be at greater risk right after sudden time changes, said Sandhu, who added that hospital staffing should perhaps be increased on the Monday after clocks are set forward.

“If we can identify days when there may be surges in heart attacks, we can be ready to better care for our patients,” he said.

The clock typically moves ahead in the spring, so that evenings have more daylight and mornings have less, and returns to standard time in the fall. Daylight saving time was widely adopted during World War I to save energy, but some critics have questioned whether it really does so and whether it is still needed.

Researchers cited limitations to the study, noting it was restricted to one state and heart attacks that required artery-opening procedures, such as stents. The study therefore excluded patients who died prior to hospital admission or intervention.