On Sunday, March 9, the eight-month-long window of doing activities outside longer in the bright, warm sunshine well after dinner will officially begin with another cycle of daylight saving time (DST). 

DST means that clocks ticking in nearly 40% of countries worldwide—including the U.S.—will “spring forward” one hour to make mornings darker and evenings lighter until Sunday, Nov. 2, when it will be time to “fall back” one hour. 

But even though DST collects more of something as beneficial as sunlight into each 24-hour passing day, it comes with a cost.  

Doctors and scientists studying the impact of daylight saving time on sleep say that if not properly prepared for, the effects of losing sleep during the time change and being exposed to light longer in the day can wreak lasting repercussions on health.

“A number of sources of data suggest that 40% of Americans are not getting adequate sleep to start with,” said Dr. Michael Jaffee, a neurologist and director of the UF Brain Injury, Rehabilitation and Neuroresilience Center. “When you have daylight saving time and you lose an hour, if you’re already starting off behind the ball, losing another full hour could be problematic.” 

American clocks have been springing forward and backward with DST almost as long as the concept has been around. According to Dr. Kenneth Wright at the University of Colorado-Boulder, Germany first introduced daylight saving time in 1916 during World War I as an energy-saving measure. 

The U.S. implemented DST as a wartime procedure shortly after in 1918 with the Standard Time Act, before repealing it a year later and reinstating it during World War II. The Uniform Time Act passed by Congress in 1966, standardized DST for all states—except Hawaii and Arizona who opted to keep traditional standard time.  

In 1973, then President Richard Nixon experimented with a year-round DST as an attempt to decrease gasoline consumption during a national oil crisis. However, longer and darker winter mornings raised concerns over children going to school in the dark after eight children in Florida were involved in car accidents. The experiment ended early the next year.  

Because of the ongoing research today revealing more negative health effects of DST, the conversation of whether to keep the biannual time change or not is still in the news. 

In 2018, Sen. Marco Rubio (R-FL) proposed the Sunshine Protection Act, a federal law that would eliminate the time change and make DST permanent. The Senate passed it unanimously in 2022, and President Donald Trump said he hopes to eliminate DST during his presidency. 

Jaffee said that if the U.S. does adjust its time change requirements again to one uniform time year-round, most scientists would suggest recognizing permanent standard time with more sunlight in the morning over DST because of how important sleep is. 

“The exposure to light in the morning is kind of the way our body resets itself or gets ready for the day,” Jaffee said. “Permanent standard time better aligns with our body’s natural circadian clocks and our body’s biology.” 

Jaffee said that sleep is a restorative function that affects every system of the body, from the heart and lungs to the GI and immune systems. For brain and cognitive function, he said sleep helps recalibrate and clear out synapses—the chemical ways that neurons communicate with each other—so that the brain can recover from the work of the day and reset for the next. 

Proper sleep can help flush out abnormal proteins in the brain that lead to Alzheimer’s disease and other forms of neurodegeneration, heal trauma to the brain and prevent ailments like high blood pressure, heart disease, diabetes, obesity, asthma, infections and depression. 

Jaffee said the ensuing health problems from sleep deprivation come more in the days following DST than from the one hour of sleep lost on the transitional day. According to the medical research publisher Open Heart, a study of hospitalizations in Michigan on the Monday following DST showed a 24% increase in heart attacks. 

“There’s an increase in motor vehicle accidents due to people that are too tired, or fatigued, or losing attention while they’re driving, and there’s other reports about occupational inefficiencies at work,” said Jaffee. “So those days do have consequences.” 

Fortunately, Jaffee said there are ways to prepare for protecting sleep hygiene without sacrificing those precious Zs. It starts with breaking down sleep hygiene into three measurable markers: quantity, quality and timing. 

Quantity of sleep focuses on the number of hours slept. Jaffee said adults should get at least seven hours of sleep a night and teenagers should aim for eight to 10. Children between ages six and 12 need even more sleep with a recommended nine to 12 hours.  

Jaffee said that while it does help to catch up on lost sleep over a weekend, maintaining a consistent amount throughout the week is preferred.  

Quality of sleep refers to how refreshing and restorative sleep was based on whether the sleeper went uninterrupted through all the sleep stages, such as slow wave and rapid eye movement sleep. 

Jaffee said a cooler room temperature can improve sleep quality, as well as avoiding stimulation and electronics before going to bed. According to a study done last month from Ambitions ABA, 71% of people sleep with their phones next to them. Jaffee said that just the buzzing of notifications is enough to disrupt sleep, and even more so is the blue light from screens.  

“Blue light has a very special frequency that can actually affect the retina in the backs of our eyes,” Jaffee said. “That blue light connects to a brain circuit which inhibits the natural melatonin release from our body which we need as a signal to tell us to go to sleep. As we’re using these electronics in the evening, we’re basically telling our body it’s not time to wind down or go to sleep and we make it harder and harder for us to make that transition.” 

Timing in sleep hygiene relates to when someone goes to bed and wakes up. Jaffee said this can be a challenge for people based on geographic locations that might be exposed to more sunlight, stressful pressures of performance faced during the day and age. 

Because adolescents are biologically wired to have a delayed phase where it’s harder to fall asleep earlier, Jaffee said they’re more vulnerable to sleep deprivation. He said DST can exacerbate this and sleep deprivation can present as attention deficiencies. 

“So often we have to get up and go to school, or go to a job, and we end up being a little bit sleep deprived, and some people will identify that as insomnia,” Jaffee said. “But actually, it’s just that their sleep cycle is delayed and it’s a matter of trying to realign their sleep cycle to something that can better fit our societal needs and demands.” 

Jaffee said that protecting sleep hygiene leading up to DST and in the days after should be done gradually as opposed to getting lots of sleep just on the night of DST. Incrementally shifting your sleep schedule of when you go to bed by 10 to 15 minutes in the days leading up to the time change can help reduce the effects of the change itself. 

In the days following the time change, Jaffee said he recommends people schedule lighter activities instead of tasks that will require them to be at their best. Once healthy sleep habits are in place around DST, it will only help to continue with them.