Every second Sunday in March marks the start of daylight saving time (DST), the annual period of the year the clocks are shifted one hour ahead. In 2023, DST officially starts at 2 a.m. on Sunday, March 12.

Jumping the clock forward to DST, and then back to standard time, every year was designed as a way to optimize daylight hours, which has been said to net energy savings, prevent traffic accidents, and reduce crime.

But for those who live in states that practice DST (parts of Arizona and all of Hawaii are the only U.S. states that don’t, according to the U.S. Department of Transportation), research is increasingly showing that the annual time change can actually have unintended detrimental consequences to health.

In fact, the American Academy of Sleep Medicine (AASM) cites short- and long-term health risks as the basis of their argument for doing away with changing the clocks altogether, according to a statement published October 2020 in the Journal of Clinical Sleep Medicine. Among such risks are metabolic syndrome and cardiovascular disease.

In the last five years, 19 U.S. states have introduced legislation to eliminate the clock change, per the National Conference of State Legislatures — though federal law does not yet allow states to adopt full-time DST. In 2021, federal legislation was introduced in Congress to help counter such restrictions. Known as the “Sunshine Protection Act,” the legislation calls for permanent DST starting on November 5, 2023.

But until such legislation passes (or doesn’t), it’s still important to prepare your body and mind for losing an hour of sleep when DST starts. Here’s what experts recommend.

Can Losing 1 Hour of Sleep Really Do That Much Harm? Research Says Yes

Cutting sleep short one hour on one night might not sound that detrimental to health at first glance, says Michael Awad, MD, chief of sleep surgery at Northwestern Medicine in Chicago. But, the lost hour can have significant effects, especially among the many of us sleeping less than the recommended seven to nine hours that is recommended to begin with, Dr. Awad explains.

The time change can also have lasting effects on your body’s internal clock beyond the first night that you “spring forward.” You can think of your circadian rhythm as the internal schedule your body follows, which helps keep daily bodily functions (not just sleeping and waking, but things like metabolism, too) regularly happening at the right times. Your internal clock is accustomed to daylight and darkness consistently happening at certain times of the day. It can take time to adjust to changes, which is why jet lag happens.

And research documents that the change does have implications on health outcomes. A review of data from motor vehicle accidents, published in February 2020 in Current Biology, revealed that the onset of DST is associated with a 6 percent surge in fatal car crashes during the first week, with a higher occurrence in Western time zones. “That’s a really significant number,” Awad says.

Similarly, a study published October 2018 in the Journal of Biological Rhythms found a significant uptick in general accidents and emergency room visits after the start of DST in the spring.

And in a study published January 2021 in the Journal of General Internal Medicine that followed healthcare workers across multiple states for eight years, researchers found there was an 18 percent increase in safety-related human errors on average for the first week of DST in the spring.

DST Disrupts Our Body Clock, Which Throws Off a Lot More Than Just Sleep

“The body doesn’t do very well when it’s asked to live in a different time zone,” says Elizabeth B. Klerman, MD, PhD, professor of neurology at Harvard Medical School and sleep research investigator at Massachusetts General Hospital in Boston. Changing the clocks for DST has similar effects to jet lag, which we know can be damaging to health over the long run.

Many body systems and processes (like sleep, digestion, and heart function) follow circadian rhythms, or patterns that stay consistent from day to day (roughly every 24 hours). These circadian rhythms trigger physical, mental, and behavioral changes in the body that keep us healthy — hormones get released in the morning to boost energy and rev up digestion, for example, according to the National Institute of General Medical Sciences (NIGMS).

Cues from the sun generally keep these circadian rhythms on track (via a network of cells in the brain referred to as the “body clock”), Awad says. But our behaviors — sleeping in much later than usual on a Saturday, spending a lot of time in the evening in front of bright screens (which the body registers as stimulating sunlight), or eating a big meal in the middle of the night — can send mixed messages to the body and misalign the body’s various circadian rhythms, too.

Traveling across time zones and switching the clocks for DST has a similar effect of misaligning your body’s clock to the one on the wall and the rotation of the sun, Awad explains. DST results in more hours of darkness in the morning, and more hours of daylight in the evening.

“Nighttime light and morning darkness shift your body to a later time, but the social clock has moved to an earlier time, so it’s harder to fall asleep and people get less sleep,” Dr. Klerman says. “And we know that many bad things happen from not getting enough sleep,” she adds.

Our bodies will of course adjust to the new schedule after a few days or a week, but there’s evidence the change may still affect our health, and more specifically heart health.

For example, in one past study, researchers found a 24 percent increase in heart attack risk the first Monday of DST in the spring. That risk tapered off over the course of the week. Conversely, the Tuesday following “fall back” was associated with a 21 percent risk reduction.

The mechanisms behind this phenomenon are still up for debate. However, it may be that DST disrupts the regular release of the stress hormone cortisol, which may increase the risk of heart attack in older adults and those with existing heart problems, according to Jamie M. Zeitzer, PhD, a research professor at the Stanford Center for Sleep Sciences and Medicine in Palo Alto, California.

Normally, your cortisol levels rise around the same time every morning to give you the energy you need to ease out of sleep and into a wakeful state. “If you’re getting up too early, that cortisol spike hasn’t happened yet,” Dr. Zeitzer says. Without cortisol to help, your heart has to work a lot harder to get you moving again, increasing your risk of heart problems.

5 Tips for Making the DST Transition Easier on Your Body

While DST isn’t going away (for now, at least), there are ways to lessen its negative effects.

1. Go in With a Good Base of Sleep

The more consistent your sleep schedule is before the switch, the less of a change your body will have to make when the time change happens, Awad says. Also be sure you’re regularly getting enough sleep. If you’re sleeping eight hours per night, one night of one hour less of sleep is going to be a lot less problematic than if you’re regularly sleeping six hours of sleep and miss an hour.

If you’re not on the healthiest sleep schedule currently, use the time change as a reminder to reevaluate how much sleep you’re getting and work on solidifying good sleep habits. “Treat sleep with the same dedication as other habits, like brushing your teeth or going to the gym,” Awad says. “It’s important.”

To establish a healthy sleep routine, try to go to bed and get up at the same time every day, use your bed only for sleep and sex, limit caffeine starting in the late afternoon, and avoid bright light exposure in the evening (switch off electronic devices at least 30 minutes before bed), per recommendations from the AASM. Keeping your bedroom cool and dark can also help ensure you fall asleep easily.

2. Shift Your Sleep Gradually Starting the Week Before DST

As DST approaches, start rolling your sleep back by about 15 minutes and moving your wakeup time 15 minutes earlier each morning. “That can help your body gradually adjust, instead of being hit with that one hour time change,” Awad says.

So, if your usual bedtime is 11 p.m., get to bed at 10:45 the Monday before DST begins. The following night, try to call it quits around 10:30, and keep going until you’ve made it to the one-hour mark.

Also, you might consider adopting other healthy bedtime routine patterns as you make these gradual changes to your sleep-wake times. As you prepare for DST, the Cleveland Clinic recommends that you avoid daytime naps, as well as caffeine or alcohol close to bedtime.

3. Push Back Your Dinner Gradually

“Another major driver of our circadian rhythm is food,” Awad says. Eating too close to bedtime can make it tough to fall asleep, because your body is too focused on digestion to think about winding down for the night.

In general, it’s a good idea to stop eating three to four hours before bedtime, Awad says. To prevent any disruption in that schedule, begin shifting your final meal (usually dinner) to an earlier time about one week before DST starts. Awad suggests shifting in 15-minute increments until you’ve hit one hour.

4. Switch All Your Clocks the Night Before DST Starts

Before going to bed the night before DST, be sure to move all your clocks ahead. Doing so may make the time change feel less confusing, says Whitney Hardy, MD, family medicine physician at Ochsner Health Center in Gretna, Louisiana. Then, you’ll be ready to live according to the new time as soon as you wake up the next day.

The Mayo Clinic says it can take two days or longer to get used to your new routine, making such changes to your clocks key to making as smooth a transition as possible.

5. Start Your Day With Sunlight

While some delay in your circadian rhythm after DST is inevitable, you can use natural sunlight to get your body clock as closely in tune with the sun clock as possible. “Getting light early in the morning is key,” Awad says.

Try to get 15 minutes of sunlight first thing in the morning. If you live in a warmer climate, you can get your sunlight outside. But even sitting next to the window while you drink your morning coffee will do the trick, Awad says. Later, avoid wake-promoting blue light from cell phones, laptops, and other electronic devices too close to bed.

But don’t necessarily consider blue light filtering glasses as a solution. Consider that one 2021 randomized controlled trial found such products were not helpful in getting better quality sleep.

How to Prep Your Body for Turning the Clocks Ahead for Daylight Saving Time