WARNING!
This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.
The repercussions associated with daylight saving time (DST) are significant and prompted the placement of California Proposition 7 on the ballot in this year's midterm election. Nearly 60 percent voted in favor to leave the state in daylight saving time all year.1
This begins laying the groundwork to give the California legislature the ability to change their clocks permanently. This is similar to a movement in August by the European Union (EU) when it announced it recommends member states stop using DST, or “summer time,” as it's known in the EU.2
While the European commission president Jean-Claude Juncker believes countries should make their own decisions, he cited a recent poll suggesting more than 80 percent of EU citizens no longer want a time change every spring and fall.3
History of ‘Fast Time’
The practice of moving the clock an hour ahead in the summer and back in the fall was initiated during World War I in the hope it would save energy, and has more to do with international conflicts and industry than with accommodating farmers.
When it was initially introduced in the U.S. in 1918 it was called “fast time.”4 The bill was signed into law by President Woodrow Wilson in an effort to support the war, and following the initiation of the same time change in Germany in 1916.
The law was subsequently repealed after the war ended, and then reinstated during World War II. Three weeks after World War II ended, the law was again repealed. This essentially threw the U.S. into a state of confusion, as state and local governments could start and stop DST as they pleased.
In 1963, Time magazine called this a “chaos of clocks.”5 It wasn't until 1966, nearly 20 years later, that order was restored with the Uniform Time Act.6 The act standardized when DST would begin and end and gave states the option to remain on standard time year-round. Hawaii and Arizona opted out and remained on standard time.
In 2016, California passed a near-unanimous resolution to eventually change DST after failing to pass legislation.7 Although the Uniform Time Act gave some structure to how clocks are set in the U.S.., it did not stop Congress from initiating changes.
In 1973, Congress determined DST should be observed all year.8 Then in 1974, the clocks were again moving forward in the spring and falling back an hour in the fall. It wasn't until 1986 that the time officially changed at 2 a.m. on the first Sunday in April and the last Sunday in October.
In 2005, Congress moved the fall date to the first Sunday in November in response to prodding from sugar lobbyists who wanted more daylight in the evening hours to accommodate trick or treaters on Halloween night.9 The current times and dates for change have been in effect since 2007. DST starts on the second Sunday of March and ends on the first Sunday in November.10
DST Does Not Reduce Energy Use
The original intention of saving energy by extending daylight hours during the summer months may actually have had the opposite effect. Although lighting had been a significant portion of energy consumption during World War I and World War II, it has become a much smaller part.
Extending daylight hours also encourages greater use of air conditioning and heating. In 2008, the Department of Energy found an almost imperceptible reduction in usage per day since the 2005 extension to include Halloween.11
A study by Yale economist Matthew Kotchen and Laura Grant, Ph.D., discovered homes and businesses in Indiana counties observing DST experienced an increase of up to 4 percent of electricity when DST was in effect.12 In another analysis of 44 different papers, researchers found that, on average, the policy helped save a mere 0.34 percent of electricity use.13
Locations further from the equator, with mild summers and low cooling demands, may save energy, but geographical locations closer actually used more energy during DST.
Kotchen notes when DST begins in the spring, people are waking during the coldest and darkest part of the day, often turning up the heat to stay warm, and during long evening hours, more air conditioning is used, leading to an overall higher energy use.
Kotchen determined that turning the clocks forward increased residential electricity demand and cost those in Indiana an extra $9 million per year, increasing emissions and impacting the environment. He notes:14 “The way people use energy now is different from when daylight saving came about.”
Increasing Traffic Accidents and Heart Attacks
The biannual clock changes also have an impact on your physical health. Researchers have noticed a statistically significant increase in the number of car accidents, workplace injuries and heart attacks in the days after the time changes in the spring. This might be related to the loss of sleep, or may have deeper biological roots in your circadian rhythms.
A University of Alabama study15 found the number of heart attacks increased by 10 percent on the Monday and Tuesday following the time change to DST in the spring. Interestingly, the number also decreased by 10 percent on the first Monday and Tuesday after the clocks are switched back in the fall.
Cardiac events are more commonplace every Monday, greater than any other day of the week, and are likely related to changes in sleep associated with the transition from weekend to workday. This is known as the “Monday cardiac phenomenon.”16 On the Monday and Tuesday following spring DST, the risk is even more pronounced.17
An earlier Swedish study18 discovered your chances of having a heart attack increase in the first three weekdays after the switch to DST, and similarly decrease when the clock is set back in the fall. Researchers compared the number of admissions on the weeks before and the Monday after DST for four consecutive years using a Michigan hospital database.19
On average there were 32 heart attacks on any given Monday, but on the Monday immediately after DST there were an average of eight additional heart attacks, suggesting to the researchers those who are already vulnerable to heart disease may be at greater risk immediately after a sudden time change.
Research data have also found road accidents increase in the first two days following DST, as do falls.20 Additionally, fatal alcohol-related traffic accidents increase for the first week after setting the clocks ahead21 and 67.6 percent more work days are lost as a result of injuries following the change to DST.22 Suicide rates for men also rise in the weeks following DST.23
Circadian Rhythms and Judgment Adversely Affected by DST
Once DST is implemented, productivity and quality of life scores drop. Till Roenneberg, a Russian chronobiologist, reports that most people show "drastically decreased productivity," decreased quality of life, increased illness, and are "just plain tired"24 in the week after DST in the spring.
Disruptions in your sleep pattern tend to cascade throughout your entire body. For instance, sleep helps reset your neural circuits that are impaired during sleep deprivation. With too little sleep, your cognitive flexibility suffers.
Research from the University of Washington found cognitive inflexibility effects even judges who are handing down sentences. On the Monday after DST in the spring, longer sentences are imposed on people who have been found guilty.25
A similar negative effect has been found in students. Researchers compared 10 years of SAT scores from Indiana where only 15 of the state's 92 counties moved their clocks forward during the study period. The data indicated an average 16-point drop in scores when students were tested after the clocks changed in the spring.26
The researchers extrapolated this data, finding the difference in SAT scores may equate to an economic loss of over $1.2 billion annually. In similar findings, researchers concluded DST adversely affected sleep patterns of high school students and their ability to be vigilant at school.27
Note: One reason Indiana is used as a discussion model for DST is because it lies smack-dab between Central and Eastern time zones. Geographically, it’s actually in the Central zone, but in 2006 it adopted the standardized DST to align with Eastern Standard Time changes. The decision has been controversial in Indiana, where the western part of the state wants to align with the Central zone, while the eastern part favors aligning with Ohio’s Eastern zone.28,29
Increasing Financial and Health Costs From DST
Financial losses are also felt in the stock market. An analysis published in the American Economic Review30 revealed an impact on the function of the financial markets each time the clocks changed. The scientists found desynchronized sleep was a reasonable explanation for the effect on the market that happened on the two weekends when the time changes, different from other Mondays. They said:31
“The magnitude of the daylight savings effect, roughly 200 to 500 percent of the regular weekend effect, is both statistically and economically significant in several international financial markets. In the United States alone, the daylight savings affect implies a one-day loss of $31 billion on the NYSE, AMEX and NASDAQ exchanges.”
Employers also suffer a significant loss in productivity. In an evaluation of how individuals were using internet access on the day following the time change, researchers examined search patterns over six years in over 200 American metro areas.32
On the Monday immediately following the time change they found an increase in searches for entertainment or related categories greater than on the Mondays before and after. They concluded, as much of this was conducted during work hours, misused internet access — called cyberloafing — was reducing productivity in workers.
Based on findings from this study, and another demonstrating an increased incidence of heart attacks, economist estimated the annual cost to the American economy each spring in lost productivity and health care was nearly $434 million.33
Keeping DST all year may also result in a reduction in crime rates. Researchers discovered that when the clocks are turned back an hour in the fall, crime rates rise. Most crime occurs between 5 p.m. and 8:30 p.m. With greater ambient lighting, criminals may have a more difficult time targeting victims.34
The researchers estimate that if DST were to remain in effect during the entire year, it could result in a $59 million annual social cost savings from robberies avoided. Since different countries change their times on different days, the airline industry estimates DST costs them an average of $147 million a year.35
Tips to Protect Your Health During DST
In addition to the strong recommendation of getting eight hours of sleep on a consistent basis, there are some other things you can do to mitigate the effects of the time change until the powers that be decide to get rid of it.
University of Alabama associate professor Martin Young suggests the following natural strategies to help your body resync after the time change:36
- Wake up 30 minutes earlier on Saturday and Sunday, to minimize the impact of getting up earlier on Monday morning
- Go outside in the sunlight in the early morning
- Exercise in the mornings over the weekend, in accordance with your overall level of health and fitness
- Consider setting your clock ahead on Friday evening, allowing an extra day to adjust over the weekend
To those recommendations, I would add:
Be particularly mindful of using electronic devices in the days prior to the switch-over. Research37 on teens shows that using electronics for four hours during the day can increase your risk of needing more than an hour to fall asleep by nearly 50 percent.
Using any device for more than two hours per day increases the likelihood of needing more than an hour to fall asleep by 20 percent. So, if you've ever considered "unplugging" for a day or two, the weekend of the DST switch-over is a perfect time to turn everything off, or cut down your use of electronics to a bare minimum so that you can optimize your sleep. |
Pay attention to your diet, making sure you are consuming plenty of fresh, whole foods, preferably organic, and minimal amounts of processed foods and fast foods; keep your sugar consumption low, especially fructose. I invite you to review our total nutrition plan here. |
Practice good sleep hygiene, including sleeping in complete darkness, checking your bedroom for electromagnetic fields, and keeping your bedroom temperature no higher than 70 degrees Fahrenheit; for a full report about how to maximize the quality of your sleep, see “Sleep — Why You Need It and 50 Ways to Improve It.” |
Optimize your vitamin D level to boost your immune function. |
Manage your stress with whatever stress-busting techniques work for you. |
Consider supplementing with melatonin if you have trouble sleeping. |
If you have a fitness tracker that tracks sleep, start using it. If you don't have one, you may want to consider getting one. During DST, making sure you're getting enough sleep may be more important than ever.
One of the keys to optimizing your sleep is going to bed early enough, because if you have to get up at 6:30 a.m., you're just not going to get enough sleep if you go to bed after midnight. Chances are you're getting at least 30 minutes less sleep than you think, as most people do not fall asleep as soon as their head hits the pillow.
Many fitness trackers can now track both daytime body movement and sleep, allowing you to get a better picture of how much sleep you're actually getting. |
Last but not least, to encourage your legislature to change DST, consider signing a petition to your Congresspersons and getting involved in your state to pass a resolution.