By Dr. Mercola
Daylight Saving Time (DST), the practice of moving clocks ahead one hour in the summer months and returning them back an hour in the winter, was first implemented by Germany during World War I, as a way to conserve electricity.
The idea, however, dates back to William Willett, an Englishman who campaigned for “summer time” in the early 1900s so that people would have more time to be out in the sunlight – though the British government was not interested.
It wasn’t until 1918 that Daylight Saving came to the US, although it was repealed a short time later, in 1919 (largely due to lobbying from the agricultural industry, whose schedules were unproductively disrupted). As reported by History:1
“Rather than rural interests, it has been urban entities such as retail outlets and recreational businesses that have championed daylight saving over the decades.”
After the 1919 repeal, there was chaos in the US, with some cities and states continuing to shift their clocks while others did not. In 1966, the Uniform Time Act was passed, which put into place the DST standard used in the US today (although certain states, namely Hawaii and Arizona, opt out).
Since the beginning, DST has been surrounded by controversy, with many arguing against it even to this day. There is reason to believe that not only does DST not conserve energy, but it may actually be putting the health of modern-day humans at risk.
Daylight Saving Time Linked to Increased Risk of Heart Attacks
The first Monday after Daylight Saving Time begins each March is met with grumbles across the US, as most lose one precious hour of sleep. This might seem inconsequential, but research is mounting showing that even slight changes to your circadian rhythm (sleep-wake cycle) can be detrimental to your health… yes, even tweaking it by just one hour.
Recent research presented at the annual scientific sessions of the American College of Cardiology revealed that the risk of having a heart attack on the Monday following DST rose by 25 percent compared to other Mondays.
At the end of the summer, when clocks are turned back one hour so that people get an extra hour of sleep, the risk of heart attack fell by 21 percent.2 Past research has similarly shown that the disruption to sleep schedules triggered by DST may pose a risk to your heart:
- Research published in the March 2013 edition of the American Journal of Cardiology 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 time.3
- 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 fall.4
- 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 five percent the first Monday after the time change, and 10 percent on Tuesday.5
Traffic Accidents, Suicides, and Workplace Injuries Also Rise After DST
DST actually leads to a host of issues for health and personal safety. One Washington University neuroscientist told CBS News that adjusting clocks forward one hour corresponds with a significant increase in traffic accidents and heart attacks6 over the next two to three days.7
One study also found that the spring transition, which causes a phase advance, is particularly hard on the average person’s sleep-wake cycle,8 and while it’s generally thought that the loss of one hour of sleep on the night of the change is inconsequential, research suggests otherwise. According to a report in Sleep Medicine Reviews:9
“…data suggests that increased sleep fragmentation and sleep latency present a cumulative effect of sleep loss [following the spring transition], at least across the following week, perhaps longer.
The autumn transition is often popularized as a gain of 1 h[our] of sleep but there is little evidence of extra sleep on that night. The cumulative effect of five consecutive days of earlier rise times following the autumn change again suggests a net loss of sleep across the week.
Indirect evidence of an increase in traffic accident rates, and change in health and regulatory behaviors which may be related to sleep disruption suggest that adjustment to daylight saving time is neither immediate nor without consequence.”
Case in point, research also shows that daylight saving time leads to increases in workplace injuries (frequency and severity)10 as well as delays in reaction time that affect performance.11 Additionally:
- Suicides: Suicide rates for males rise in the weeks following the start of DST.12
- Automobile Accidents: Traffic accidents increase by eight percent on the Monday following the changeover to DST.13 And fatal alcohol-related traffic accidents increase for the first week after setting the clocks ahead.14 Workplace accidents and injuries increase by 5.7 percent, and 67.6 percent more workdays are lost as a result of injuries following the change to DST.15
- Productivity and Quality of Life: People are less productive once DST is implemented. Till Roenneberg, a Russian chronobiologist, reports that most people show “drastically decreased productivity,” decreased quality of life, increased illness, and are “just plain tired” following the switch to DST.16
Is Tweaking Your Sleep-Wake Cycle by One Hour Really That Big of a Deal?
Disruptions to sleep tend to cascade outward throughout your entire body. There’s a lot we still don’t know, but increasingly more that we do – and one hour really does make a difference.
Research has shown, for instance, that when participants cut their sleep from 7.5 to 6.5 hours a night there were increases in the expression of genes associated with inflammation, immune excitability, diabetes, cancer risk, and stress.17 In other words, getting just one hour less sleep a night may raise your risk of multiple chronic diseases. Interrupted or impaired sleep can also:
- Increase your risk of heart disease and cancer
- Harm your brain by halting new neuron production. Sleep deprivation can increase levels of corticosterone (a stress hormone), resulting in fewer new brain cells being created in your hippocampus
- Contribute to a pre-diabetic, insulin-resistant state, making you feel hungry even if you've already eaten, which can lead to weight gain
- Contribute to premature aging by interfering with your growth hormone production, normally released by your pituitary gland during deep sleep (and during certain types of exercise, such as high-intensity interval training)
- Increase your risk of dying from any cause
Daylight Saving Time Isn’t Really ‘Saving’ Anything
The health risks might be worth it if you could prove that Daylight Saving Time was resulting in major gains elsewhere, such as energy conservation. But the truth is, the energy conservation touted when DST became a national standard likely no longer apply because, in the 21st century, most people are not spending that extra daylight hour outside in the sunshine – they’re spending it indoors where it’s cool.
The irony is that the air conditioner costs far more energy to run than do the lights…The fact is, Daylight Saving Time is not actually saving anything… more accurately, we are sacrificing our health and safety due to this outdated and impractical time change. As reported by History:18
“Dating back to Willett, daylight saving advocates have touted energy conservation as an economic benefit. A U.S. Department of Transportation study in the 1970s concluded that total electricity savings associated with daylight saving time amounted to about 1 percent in the spring and fall months.
As air conditioning has become more widespread, however, more recent studies have found that cost savings on lighting are more than offset by greater cooling expenses. University of California Santa Barbara economists calculated that Indiana’s move to statewide daylight saving time in 2006 led to a 1-percent rise in residential electricity use through additional demand for air conditioning on summer evenings and heating in early spring and late fall mornings. Some also argue that increased recreational activity during daylight saving results in greater gasoline consumption.”
How to Counteract the Effects of Daylight Saving Time (And Other Disruptions to Your Circadian Rhythm)
Small shifts in circadian timing occur all the time, not only due to Daylight Saving Time. In the 21st century, 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).
People are increasingly pushing the limits of their body clocks, getting up early and staying up late for a myriad of reasons. These reasons, it turns out, may not be worth it when it comes to your long-term health. Making small adjustments to your daily routine and sleeping area can go a long way to ensure uninterrupted, restful sleep and, thereby, better health. I suggest you read through my full set of 33 healthy sleep guidelines for all of the details, but to start, consider implementing the following changes:
- Avoid watching TV or using your computer in the evening, at least an hour or so before going to bed. These devices emit blue light, which tricks your brain into thinking it's still daytime. Normally, your brain starts secreting melatonin between 9 and 10 pm, and these devices emit light that may stifle that process. Even the American Medical Association now states:19
- Make sure you get BRIGHT sun exposure regularly. Your pineal gland produces melatonin roughly in approximation to the contrast of bright sun exposure in the day and complete darkness at night. If you are in darkness all day long, it can't appreciate the difference and will not optimize your melatonin production.
- Sleep in complete darkness, or as close to it as possible. Even the slightest bit of light in your bedroom can disrupt your body’s clock and your pineal gland's melatonin production. Even the tiniest glow from your clock radio could be interfering with your sleep, so cover your radio up at night or get rid of it altogether. Move all electrical devices at least three feet away from your bed. You may want to cover your windows with drapes or blackout shades.
- Install a low-wattage yellow, orange, or red light bulb if you need a source of light for navigation at night. Light in these bandwidths does not shut down melatonin production in the way that white and blue bandwidth light does. Salt lamps are handy for this purpose.
- Keep the temperature in your bedroom no higher than 70 degrees F. Many people keep their homes too warm (particularly their upstairs bedrooms). Studies show that the optimal room temperature for sleep is between 60 to 68 degrees.
- Take a hot bath 90 to 120 minutes before bedtime. This increases your core body temperature, and when you get out of the bath it abruptly drops, signaling your body that you are ready to sleep.
- Avoid using loud alarm clocks. Being jolted awake each morning can be very stressful. If you are regularly getting enough sleep, you might not even need an alarm.
- Get some sun in the morning, if possible. Your circadian system needs bright light to reset itself. Ten to 15 minutes of morning sunlight will send a strong message to your internal clock that day has arrived, making it less likely to be confused by weaker light signals during the night. More sunlight exposure is required as you age.
- Be mindful of electromagnetic fields (EMFs) in your bedroom. EMFs can disrupt your pineal gland and its melatonin production, and may have other negative biological effects as well. A gauss meter is required if you want to measure EMF levels in various areas of your home.