By Dr. Mercola
Daylight saving time (DST), the practice of moving the clock one hour ahead in the summer and then back an hour in the fall, was used during World War I in the hope it would save energy.
Over the coming decades, the world experienced unexpected repercussions from the time change — so much so, in fact, that many would like to stay on one time, all the time.
The issue of abolishing DST is backed by good reasons and scientific evidence. The original intention was to give you more access to daylight hours, but you may experience mental and physical consequences in the days and possibly weeks surrounding the time change.
There doesn't appear to be good reason to continue to keep DST, but changing it may take several more years. Since inception, the idea of DST has been surrounded by controversy. Today research demonstrates it does not save energy and may instead pose a risk to public health.
History of Fast Time
When DST was first introduced in the U.S. in 1918, it was called "fast time."1 The bill initiating DST was signed into law by then President Woodrow Wilson to support the war effort, following the initiation of the same time change in Germany in 1916, for the same reason.
But it was in 1908 that DST was first used in Thunder Bay, Ontario, Canada. It was Englishman William Willett who proposed the idea in a brochure he published in 1907 called "The Waste of Daylight." He worked for the next eight years to initiate DST in the U.K., but died in 1915 without seeing his idea come to fruition.2
The U.S. law was repealed after the war ended and then reinstated during World War II. It was again repealed three weeks after the second world war ended, throwing the U.S. into a state of confusion, as states and local governments could start and stop DST as they pleased. In 1963, Time magazine called this "a chaos of clocks."3
Order in the U.S. was not restored until 1966 with the Uniform Time Act. Although the Act standardized when DST would begin and end, it also gave states the option to remain on standard time year round. Hawaii and Arizona opted out and remained on Standard Time year-round.
After a failed attempt in 2016 to pass legislation,4 California passed a near unanimous resolution aimed at eventually changing DST.5 Golfing enthusiasts, baseball fans6 and others enjoy the longer daylight hours in the summer months, but it does come at a cost.
Although the Uniform Time Act provided some structure to how clocks are set in the U.S., it hasn't stopped Congress from making changes over the years. For instance, in 1973 Congress determined DST should be observed all year.7
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.
Congress moved the fall date again in 2005 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.8
Since 2007, thanks to the Energy Policy Act of 2005, DST starts the second Sunday of March and ends the first Sunday in November.9
DST Changes Found to Trigger Physical Problems
Another reason DST was kept after the war was to increase the hours of daylight during times children were playing outside, in the hope of reducing the number of children hit by cars.
Research has not proven a statistical increase or decrease in pedestrian versus car accidents.10 However, there is a spike in fatal traffic accidents in the days after DST in the spring, likely related to a lack of sleep.11,12
Improvement in sleep patterns may also prevent the number of migraine and cluster headaches associated with DST,14,15 and reduce the number of workplace injuries that occur in the days following DST.16 During the switch to DST, the numbers of heart attacks and strokes also rise.17,18
There is normally an increased number of heart attacks experienced on Monday mornings, but following DST in the spring, even that number is elevated. A shift in sleep-wake hours also increases the risk of stroke on the start and stop of DST days.19
• Research published in 2013 showed a small rise in heart attack rates the Sunday following the shift to DST, along with a small tick downward the Sunday following the change back to standard time20
• A 2012 University of Alabama study found that heart attacks increased by 10 percent on the Monday and Tuesday following the time change to DST. Heart attacks again decreased by 10 percent on the first Monday and Tuesday after clocks are switched back in the fall21
• A 2008 Swedish study found your chances of having a heart attack increase in the first three weekdays after the switch to DST, and decrease after you set your clock back to standard time in the fall. Heart attacks increase by 5 percent the first Monday after the time change, and 10 percent on Tuesday.22
DST Affects Work Productivity and Mental Heath
Lack of sleep also contributes to a lack of productivity and creativity in the workplace. The incidence of "cyber-loafing," or employees spending more time on their computers in non-revenue producing activities, increases in the week following DST in the spring.23 A study in 2007 suggested you may never fully adjust to DST.24
Researchers theorize your natural biological clock, controlled by hormones, doesn't respond to social changes in time, but rather changes in natural lighting. Further research identified the effect of DST on secretion of cortisol, your stress hormone, in a large population study.25
Cortisol naturally reaches the lowest level in the middle of the night and peaks in the morning hours. During DST, researchers found cortisol peaked almost an hour later than it did after DST ended.
A German study26 found when the clock switches forward in spring, employees suffered a negative impact on their well-being for a full week. In males employed full-time, the effect was twice as large as other participants.27
During the fall, when you get an extra hour of sleep, you may also have a higher risk of depression. Based on the analysis of over 185,000 people over seven years, researchers found an 11 percent increase in the number of people who suffered from a unipolar depressive episode in the 10 weeks after the end of DST.28
DST-Induced Cognitive Inflexibility May Impact Your Decisions
Sleep helps reset neural circuits that are impaired during sleep deprivation. These circuits must be tuned with adequate sleep to improve your decision-making skills. With too little sleep, your cognitive flexibility begins to suffer. As noted by Dr. Michael Halassa, assistant professor of neuroscience at New York University:29
"To be flexible you have to be able to process a lot of info. People default to a lower processing capacity when they can't process a lot of information."
Researchers at the University of Washington found cognitive inflexibility affects even judges who are handing down sentences. On Monday after DST in the spring, longer sentences are imposed on people who have been found guilty.30
Researchers took into account other factors that may impact a judge's decision, but continued to find a statistically significant difference on the Monday after DST. Lead researcher Kyoungmin Cho, of the University of Washington, commented on the results and how they may be extrapolated to other authority figures:31
"We find that the sentences given to those convicted of crimes may be partially polluted by the sleep of those giving the punishments. Sleep is a factor that should not play a role in their sentences, but does. Across many alternative analyses and robustness checks, the effect was still quite clear and meaningful.
Bosses punish employees who break work rules, parents punish children who engage in bad behavior, teachers punish students who disrupt the classroom environment, and sports referees punish players and athletes who violate the rules of the game.
Many of the people making these punishment decisions will do so while short on sleep, and the same logic explored in our research will likely apply in those contexts, as well."
Economic Impact of DST
The original intention of saving energy by extending daylight hours may have had the opposite effect. In 2008, the Department of Energy found an imperceptible reduction in energy per day since the 2005 extension to encompass Halloween.32
However, in 2011, a study by economists Matthew Kotchen and Laura Grant, Ph.D., discovered something entirely different.33 In their study of homes and businesses in Indiana counties that began observing DST, researchers discovered an increase of up to 4 percent of electricity during DST.
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, the 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. The researchers wrote:35
"Results show that daily cases of robbery, a violent and socially costly street crime, decrease by approximately 7 percent in the weeks after DST begins, with a 19 percent drop in the probability of any robbery occurring. A 27 percent decrease in the robbery rate during the sunset hours drives much of this result."
In 1986, an extra month of DST was worth between $200 million and $400 million to manufacturers of barbecue equipment and the golf industry.36 However, not all businesses post a gain with DST; others experience a loss. Since different countries change their times on different days, the airline industry estimates DST costs them an average of $147 million a year.37
The total cost to the U.S. annually from the time change is estimated to be $434 million. This number was calculated on lost work productivity and health challenges from poor sleep on one night.38
What Has to Happen to Eliminate DST?
Federally, the Uniform Time Act prohibits individual states from starting or stopping DST on dates other than the one mandated by the federal government and it bars them from adopting it full-time.39 The three states that do not change their time keep Standard Time year round.
Doing this effectively disrupts the uniformity of the geographical area, impacting travel, interstate commerce and even banking. In order to make this work efficiently, states must band together to make the change. Scott Yates, a DST activist, has familiarized himself with both the laws governing time change and the impact on people and the economy. He commented:40
"It used to be a weird, niche, oddball issue, but it's become much more of a public-policy issue. The research shows that the thing that's the problem is the changing twice a year. I've seen this over and over, in state after state — somebody proposes a bill to stay on daylight saving, then somebody looks up the law and figures out that they can't. Every one of those bills is doomed."
Yates has a different plan. While the state bills are not a feasible option, each state could pass a nonbinding resolution requesting the U.S. Department of Transportation (federal authority over DST), to assign a new time zone equivalent to either local standard time or DST. Yates explains his proposed use of resolutions, like the one passed in California in 2016:41
"Resolutions aren't usually thought of as having any power. They don't have the force of law; they're for, like, recognizing the teacher who retired after 50 years. But, once in a while, we call on Congress to enact X, Y or Z. My thinking is that it's just political expediency: It's easier to pass a resolution than a law.
If I can get maybe a dozen states to pass a resolution, I can go to the Department of Transportation myself and say, 'The will of the people, as represented by the states, is they don't want to change their clocks twice a year.' They could ease the restrictions so that everybody can pick the time zone they want to be in, and then no more time changes. There's a big enough stink building that I think I can do it."
Tips to Surviving DST
Until DST is either abolished or remains in place year-round, you'll have to accommodate your sleep schedule twice a year. There are several ways you can reduce the physical and mental effects from the time changes I outline in the video above. I suggest you read through my full set of 33 sleep guidelines for all of the details.
Small shifts in circadian timing occur all the time, not only during DST. Today, many people ignore their body's internal clocks, either by necessity (working the night shift or remotely with co-workers across the globe) or choice (staying up late surfing the Web or watching TV). However, making small adjustments to your daily routine and sleeping area can go a long way to ensure uninterrupted, restful sleep and, thereby, better health.