Daylight saving time (DST) has become a great source of debate. This is because new research repeatedly shows that daylight saving time is tied to serious health problems like cardiovascular events, traffic accidents, and immense sleep loss due to the jarring effect of the time shift on the body’s circadian rhythm.
Although daylight saving time was initially implemented as a cost-saving measure to reduce energy consumption during wartime, it is still widely practiced worldwide and in the United States.
DST disrupts the body’s normal circadian rhythm, even with just an hour's time shift.
There is an increased incidence of numerous health problems immediately after the start of DST, including heart attacks, strokes, and traffic accidents.
Preparing your body for the time shift in the week leading up to DST can help prevent the negative effects of DST.
Luckily, there are several steps one can take to lessen these effects and prepare for the clock change ahead of time.
What is daylight saving time?
Daylight saving time is the practice of a twice-yearly time change that involves shifting our clocks ahead one hour as warmer weather approaches and back one hour as it becomes colder again. This time shift provides more daylight at the end of the day, which allows people more time for outdoor activities in the evening. Most countries in North America and Europe observe DST, along with countries like Australia, Haiti, and several nations in South America and Asia.
Origin of daylight saving time
In the United States, DST was initially instituted as a wartime measure in the early 1900s to save on energy costs. It meant that because of the extra daylight, people used fewer resources like kerosene and candles to illuminate the indoors at night.
Currently, it is still a federal law to continue to observe DST in the United States. In recent years, however, there has been increasing debate regarding whether DST should be abolished since more data show that the time change, even if just by one hour twice a year, causes significant health consequences for humans.
DST effects on the circadian rhythm
Sunlight is the most powerful signaler to the human body in establishing an internal circadian rhythm. During the daytime, when the sun is at its highest and the eyes transmit strong light cues to the brain, the body knows to be awake and active. As the sun begins to set and light decreases, the body is cued to get ready for sleep. This cycle is repeated on a twenty-four-hour basis and is what guides the body's natural circadian rhythm.
When the external clock suddenly shifts an hour during DST, the body’s internal circadian rhythm no longer aligns with external light signals. This sudden misalignment and pressure to adjust the internal clock forward an hour cause the health issues associated with DST.
Health consequences of daylight saving time
Daylight saving time is known to have harmful health effects. In the week after the start of DST, data show an increased incidence of strokes, heart attacks, and acute episodes of atrial fibrillation. In addition, because of the circadian misalignment that occurs with the sudden time shift, people experience a heavy burden of sleep loss and sleep debt. This loss of sleep has been tied to an increase in motor vehicle accidents by up to 6% in the days following the DST time change. People even miss more routine medical appointments in the first few days after DST, and as a result, there is an uptick in emergency room visits.
How to prepare for DST
There are several steps you can take to prepare your body for DST. The American Academy of Sleep Medicine suggests several actions you can take to get ahead of the time shift.
Go to bed earlier
In the week leading up to the start of DST in March, going to bed 10–15 minutes earlier each evening can help your body’s clock avoid the sudden shock of the time change, making it easier to adjust once DST occurs.
Adjust the timing of activities
Similarly, you can adjust the timing of other activities like dinner back by 10–15 minutes each day as well. This also reinforces bodily preparation for the circadian shift that needs to occur after the start of DST.
Saturday night: adjust your clock, then go to bed at your regular bedtime
The daylight saving shift occurs early Sunday morning. Before this occurs, on the Saturday immediately preceding DST, keep to your usual routine, then change your clock forward sometime in the early evening hours. This could be right after dinner time, for example. Then go to bed at your normal time based on the updated clock time. Again, keeping consistency with your bedtime as much as possible is key to facilitating the time adjustment.
Get sunlight early on Sunday
Light exposure is the best way to help your body learn to align with the new time. So on DST Sunday, make sure you get some early morning sunlight. This will also help your internal clock catch up with the time change.
If you are really tired, take a quick nap
If you find that you have not slept well going into Sunday morning with the time change or are feeling groggy, it is okay to take a short nap if absolutely needed. However, be sure to limit the nap to longer than 15–20 minutes; otherwise, you may set yourself up for more sleep difficulty that evening.
Although an hour may seem like a minor time change, DST profoundly affects human functioning, health, and biological rhythms. Data continue to show that the time shift of DST is associated with increased traffic accidents, sleep loss, and significant cardiovascular events. While legislation to permanently abolish DST is pending in the United States, there are steps you can take to ease the time adjustment in the meantime. First, start preparing the week before by slowly adjusting your bedtime and daily activities. Try to keep a regular daily routine, and make sure to get adequate sunlight on the first day of DST. Then, when the time shift occurs, you will be better equipped to manage while lessening the negative effects on your sleep and health.
- Journal of Clinical Sleep Medicine. Daylight saving time: an American Academy of Sleep Medicine position statement.
- American Academy of Sleep Medicine. Saving daylight, losing sleep: Insomnia Awareness Day is March 10.
- Journal of Biological Rhythms. Why should we abolish Daylight Saving Time?
- Sleep Medicine Reviews. The impact of daylight saving time on sleep and related behaviours.
- Accident Analysis and Prevention. Accident rates and the impact of daylight saving time transitions.
- PLOS Computational Biology. Measurable health effects associated with the daylight saving time shift.