How Our Health Falls Back When We Spring Forward
- Article previously published in the Hudson Valley Pilot – see link below
As we approach Daylight Saving Time (DST) on March 12, 2023 many of us easily recognize the annoyance of not only resetting all our clocks, but also of losing an hour of sleep as we spring ahead. We trade this lost hour of sleep for an extra hour of daylight in the evening, but at what cost?
The National Sleep Foundation’s 2021 Sleep in America Poll revealed that 70% of Americans don’t think their sleep, routines or mood are disrupted by changing the clocks. In the same poll, while only 1 in 4 Americans want to keep the biannual clock change, greater than 50% felt the US should stay in DST year-round. There are many in government who feel the same way, as evidenced by the Senate’s unanimous passing of the Sunshine Protection Act in March 2022. It is now up to Congress to determine the adoption of DST permanently come November 2023. Fortunately, the US House of Representatives stalled on their vote last year, as the science is mounting that not only is the shifting back and forth detrimental, but that stealing the hour of daylight from the morning can have measurable impacts on health.
Why we have DST
While the idea of saving daylight was bantered around by Benjamin Franklin as early as 1784, DST wasn’t formally conceived until the late 1800s, and had not actually been put into action anywhere until the German empire made it a national practice in 1916 as a way to conserve coal during the war. The idea behind DST was to maximize our wakeful exposure to sunlight in the Northern Hemisphere, as daylight starts to lengthen in the spring. Britain and its allies soon followed, with the US adopting a 7 month shift in 1918. While most countries abandoned it after the war ended, this “War-time” practice, as it was known then, came back year-round during WW II. Most of the United States has officially observed DST since passage of the Uniform Time Act in 1966 (Hawaii, certain areas of Arizona, and the U.S. territories of American Samoa, Guam, the Northern Mariana Islands, and the U.S. Virgin Islands do not practice DST).
In the time of candles, gas lamps and the first World War, this shift toward evening daylight may have made sense so that darkness fell later according to the clock time. This likely did allow for the conservation of energy resources. But in this modern era of electric light and air conditioning, the amount of actual energy conserved is negligible. According to Michael Downing, a lecturer at Tufts University and author of the book “Spring Forward: The Annual Madness of Daylight Saving Time”, it doesn’t cut our energy use. “In fact, when we lose an hour’s sleep as the eight-month DST season begins, it will not reduce our electricity use even by one half of 1 percent” Downing says. Furthermore “gas consumption goes up during daylight saving time—something the gas industry has known since the 1930s. That’s why it lobbied hard to reintroduce DST” states Downing. When humans have more daylight in the evening, they go to more places, and typically drive to these places, and as we know, extra driving means more carbon dioxide in the atmosphere, which also exacerbates climate change.
Health consequences of changing the clocks
Looking beyond politics though, the evidence is mounting that the twice yearly clock change has measurable effects on our health. A landmark study in 1999 by researchers at Johns Hopkins and Stanford University analyzed 21 years’ worth of fatal car crash data and found a notable increase in car crash deaths on the Monday after the switch to DST; 83.5 deaths, compared with 78.2 deaths on the average Monday. There is also evidence showing a 5.7% increase in work related injuries, and a significant increase in the severity of these injuries.
More surprisingly however, cardiologists are recognizing a detrimental pattern in the rates of cardiovascular disease in the spring. A study in the Open Heart Journal from 2014 revealed a 24% increase in heart attacks on the Monday following the spring shift, and a 21% reduction on the Tuesday following the fall changes. Similarly, a 2015 study in Sleep Medicine found the rate of stroke was 8% higher the first 2 days after springing forward. Health practitioners also note exacerbations in existing mental health conditions, such as depression or anxiety, as well as in a host of neurologic disorders including headaches, Alzheimers and Parkinsons diseases .
While the exact mechanisms driving these physiologic changes are under investigation, it has become increasingly clear that circadian rhythms involve more than just the sleep-wake cycle.
The circadian rhythm, as the latin name implies, is a roughly 24 hour internal process that optimizes the running of nearly all life forms, from unicellular organisms to humans. Our master clock, known as the supra-chiasmatic nucleus, sits behind our eyes, just above the crossing of the optic nerves in the part of our brain known as the hypothalamus. This positioning makes it easy to understand why light is such a powerful metronome for this internal clock to pace its signals to the rest of the body. The most easily recognized of these rhythms is the sleep-wake cycle, however, circadian rhythms control many other body processes. For instance, your digestive system produces proteins to make sure you eat on schedule, and the endocrine system regulates hormones to match your energy expenditures during the day. In addition, circadian rhythms are emerging as important regulators of specific immune functions as well.
Over the last few decades there have been remarkable advances in neurobiology and our understanding of sleep wake cycles and circadian rhythms and a growing body of evidence to suggest that the harm is not only in the amount of sleep disruption that occurs with the biannual clock change, but there are significant health consequences with a potential move to permanent DST.
Why Permanent DST is Bad for Health
Interestingly, our biological clocks are not timed perfectly to the sun; they actually run about 10-15 minutes longer than 24 hours. As we trade the morning light for evening light, we shift our social clocks away from the sun’s clock, and this shift in the timing of daylight exposure can affect the body’s internal clock. “Every single day, we’re fighting an uphill battle to fall asleep and wake up on time, and every day we have a natural instinct to stay up a little later,” says Dr. Schneider, clinical assistant professor at Stanford Health Care and former chair of the AAN Sleep Medicine Section. “The only way to fight that is to get early morning bright light exposure. That disappears more and more in the winter months.”
Groups such as the American Academy of Sleep Medicine and the National Sleep Foundation, as well as many experts, oppose permanent daylight saving time and prefer the idea of permanent standard time. According to the Sleep Foundation “Daylight saving time reduces exposure to morning sunlight, which makes it harder to wake up in the morning. More light in the evening may make it harder to fall asleep at night”. With a shift to permanent DST there will be many places in the US that don’t see the sun rise until 9 am in the winter months.
Waking up in the darkness is not healthy, and whenever we are awake when it is dark outside it causes a change in our circadian rhythms by affecting our melatonin and cortisol levels. Moreover, we need the early morning light to reset our circadian rhythms. According to Dr Karen Johnson, professor of neurology at UMass Chan Medical School—Baystate and chair of the AAN Sleep Medicine Section, “One of the reasons we see more of the detrimental health effects of the DST-standard time shift in the spring, when we spring forward, is not just because we’re losing an hour of sleep, although that’s a factor,” Dr. Johnson said. “It’s also because we’re transitioning to a time that is less favorable for most people.”
According to the CDC, one third of Americans report not getting the 7-9 hours of sleep recommended for adults. Furthermore, this chronic sleep deprivation is linked to a host of chronic diseases, including cardiovascular disease, obesity, diabetes and depression. The further dysregulation of cortisol and melatonin levels that will occur with permanent circadian misalignment will further contribute to stress, altered metabolism, and inflammation. It is unclear why there is such governmental support for a permanent change to DST when sleep deprivation is now recognized as a national health crisis, and increasing the proportion of adults who get enough sleep continues to be an objective of Healthy People 2030.
As a person who has spent most of her professional life in a state of chronic sleep deprivation, I am certainly late to the party on prioritizing good sleep. But I have been able to see first hand the cognitive benefits of aiming for at least 7 hours a night. It is unclear how Congress will proceed on this vote this year. As there are so many factors in our modern lifestyles that impact the quality and quantity of our sleep, I am hopeful that a forced shift to permanent DST will not become one of them. Understanding the science behind the collision of our social, biologic and solar clocks is imperative for our health.
