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The Cost of Daylight Savings

By Mary Bullock Cooper

Spring forward an hour in March or fall back an hour in November… you know the drill. It’s once again that time of year when everyone asks themselves, “Why do we do this?” Daylight savings time (DST) has been around in the United States since 1918 when it was created by the Standard Time Act. The US first implemented DST during World War I as a means to increase workday production by reducing the cost of energy and elongating the shorter, darker days of winter. This policy went out of effect at the end of the war, but was soon reinstated in World War II. After WWII, daylight savings time was permanently written into law in the United States with the Uniform Time Act in 1966. The overall purpose of switching to DST over Standard Time (ST) to increase the number of light hours in the afternoons made sense at the time it was created. Energy costs were high and large scale production required more daylight hours, but we have since made advances in energy production that make this problem obsolete. For a more comprehensive review on the legislation and history of daylight savings check out: Why are legislators trying to get rid of daylight savings? Now that we are well past the events and energy costs of the World Wars, daylight savings is still a regular part of our lives. But, should it be? In this article we are going to talk about daylight savings and what these supposed “savings” cost in terms of human health.

…daylight savings is still a regular part of our lives. But, should it be?

To understand how daylight savings affects the human body, we must discuss circadian rhythms. Simply put, circadian rhythms are patterns of behavior and biological/physiological processes that follow a roughly 24 hour cycle (Aschoff et al., 1976). These patterns can be seen in all organ systems and tissues throughout the human body (National Institutes of Health, 2022). For example, typical peak alertness occurs around 10 am, while peak muscle strength occurs at 5 pm (Marsi et al., 2018). The master clock for circadian rhythms is located in the Suprachiasmatic Nucleus (SCN), an area of the hypothalamus that receives light input from the retina. The SCN contains a clock composed of genes and signaling molecules that take in light information and tell the rest of the body what time it is. The rest of the body has many similar clocks that maintain rhythms in tissues throughout the body (National Institutes of Health, 2022), including some that are trained to follow hormonal cues from the SCN. In simpler terms, the SCN tells the rest of the body what time it is using a light-sensitive circadian clock.

Each circadian clock is driven by a set of genes, called clock genes, that turn themselves on and off in a feedback loop in order to produce rhythms in protein levels and, therefore, rhythms in cellular function. These rhythms influence things like metabolism, cognition, sleep-wake cycles, and many more processes that affect our health. These rhythms are not only important for human health, but are strongly affected by the timing of the daily solar cycle. Meaning, if you change the light cycle through daylight savings, you disturb your body’s natural circadian rhythms (Blume et al., 2019).

[Circadian] rhythms are not only important for human health, but are strongly affected by the timing of the daily solar cycle

In the words of Phyllis Zee, “Science has evolved over the last decade to show the transition between standard time and DST is associated with adverse health consequences. The big question on the table right now is, should it be permanent standard time or permanent daylight savings time?” (Northwestern, 2021 ). This is, in fact, a big question as many neurological diseases (e.g. Alzheimer’s and Parkinson’s) are associated with, or aggravated by, disruption of circadian rhythms (Musiek, 2016). The shifts in sleep and wake cycles that result from daylight savings could naturally impact those who suffer from these diseases, as well as healthy individuals with no underlying disease.

Disruptions to the light cycle, such as reducing exposure to morning light during daylight savings time, has a direct impact on health through circadian rhythms. Light is known as a powerful environmental cue that modifies circadian rhythms across the body (Duffy et al., 2005). In circadian science, “entrainment” refers to the synchronization of all of the circadian rhythms across the body to an environmental cue, such as light. For example, when you fly to the other side of the world and stay there, your circadian system will eventually entrain your body’s circadian rhythms to match your new timezone, instead of maintaining the same rhythms you had in a previous timezone. Now imagine you were to actually fly across the country for an extended stay. How do you feel once you arrive in a new timezone? A common occurrence is jet lag, which occurs when you enter a new time zone with your circadian rhythms aligned to the original timezone, and your body struggles to stay awake in your new location. This is a classical example of shifted circadian rhythms.

Daylight savings is not the same as jet lag, but many of the same principles of circadian disruption apply. In fact, chronic jet lag is induced in lab mice in order to research the effects of circadian disruption. The short term effects of daylight savings mirror those of jet lag: sleep disturbances, fatigue, and changes in blood pressure are all common in the days following the time switch. Additionally, following the week of the time-shift to daylight savings, there are increased rates of cardiovascular disease, heart attacks, car accidents (likely due to fatigue or cognitive impairment), stroke, depressive episodes, and immune-related disease (e.g., colitis) (Northwestern, 2021).

…sleep disturbances, fatigue, and changes in blood pressure are all common in the days following the time switch (to daylight savings)

If all of these factors were not enough to convince you to rethink daylight savings, the negative effects of daylight savings continue long after the initial switch from standard time to daylight savings. In fact, studies show that daylight savings and the circadian disruptions it produces are linked to higher reports of depression, slowed metabolism, metabolism impairment, and headaches. These changes are linked to increased risk of developing cognitive impairment, cardiovascular disease, and problems with digestive health (Northwestern, 2021). These long-term and short-term disruptions add up to a troubling combination for brain health and call for a reevaluation of the current state of daylight savings policy.

So, what do we do? Researchers and legislators are currently fighting to end daylight savings’ biannual time change in order to permanently synchronize our internal clocks to the rotation of the earth and seasonal changes. Currently, the “Sunshine Protection Act” has passed in the Senate. This act would end the time change and allow for permanent DST as the new standard time. This bill now awaits more deliberation from the House of Representatives. Meanwhile, daylight savings time is now in full effect for 2023.

Until we have an answer from our legislators, there are some steps you can take to promote healthy circadian rhythms as we once again get used to daylight savings time. First, the main problem with daylight savings is that when we spring forward an hour, we lose an hour of morning sunlight. Exposure to early morning sunlight is crucial for entertainment of healthy circadian rhythms, so waking up a bit earlier and maximizing the time you spend in morning light is a great protective measure of your circadian rhythms. Second, maintaining good sleep hygiene can promote healthy circadian rhythms during daylight savings. Ensuring you limit sleep disruptions (e.g. light, noise, technology) during sleep and enforcing a consistent bedtime can greatly benefit not only circadian rhythms, but your general health (Center for Disease Control and Prevention, 2020).

Daylight savings time may be unavoidable for the time being, but hopefully now you are more informed about the consequences and protective measures of circadian rhythms in order to promote healthy rhythms despite current policies. So, as you adjust your clocks this week, remember the cost of daylight savings.

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Written and Illustrated by Mary Cooper
Edited by Talia Oughourlian and Anastasiia Gryshyna

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References

Aschoff, J., & Wever, R. (1976). Human circadian rhythms: a multioscillatory system. Federation proceedings, 35(12), ..

Blume, C., Garbazza, C., & Spitschan, M. (2019). Effects of light on human
circadian rhythms, sleep and mood. Somnologie : Schlafforschung und Schlafmedizin = Somnology : Sleep Research and Sleep Medicine, 23(3), 147–156. https://doi.org/10.1007/s11818-019-00215-x

Center for Disease Control and Prevention. (2020) Effects of Light on Circadian Rhythms.

Duffy, J. F., & Wright, K. P., Jr (2005). Entrainment of the human circadian system by light. Journal of biological rhythms, 20(4), 326–338. https://doi.org/10.1177/0748730405277983

National Institutes of Health. (2022). Circadian rhythms. National Institute of General Medical
Sciences.

Northwestern Medicine. (2021). Daylight saving time and your health. Northwestern Medicine.

Masri, S., Sassone-Corsi, P. The emerging link between cancer, metabolism, and circadian rhythms. Nat Med 24, 1795–1803 (2018). https://doi.org/10.1038/s41591-018-0271-8

Musiek, E. S., & Holtzman, D. M. (2016). Mechanisms linking circadian clocks, sleep, and neurodegeneration. Science, 354(6315), 1004–1008. https://doi.org/10.1126/science.aah4968

The Uniform Time Statute. 15 U.S.C. §§ 260-64 (1966) https://www.transportation.gov/regulations/time-act#:~:text=Today%2C%20the%20Uniform%20Time%20Act,change%20a%20time%2Dzone%20boundary.

Author

  • Mary Cooper

    Mary Cooper is a Graduate Student in the Departments of Neurology and Psychology at the University of Alabama at Birmingham (UAB). She uses a range of techniques including mRNA hybridization, EEG, and behavioral machine learning programs to study circadian influences on Alzheimer’s Disease. Mary’s scientific pursuits outside the lab are to make useful connections between classical arts and academic sciences. She is a contributor and volunteer at the Brain Awareness Week celebrations in Birmingham, Alabama. In her spare time, Mary is a pianist, gardener, and painter.

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Mary Cooper

Mary Cooper is a Graduate Student in the Departments of Neurology and Psychology at the University of Alabama at Birmingham (UAB). She uses a range of techniques including mRNA hybridization, EEG, and behavioral machine learning programs to study circadian influences on Alzheimer’s Disease. Mary’s scientific pursuits outside the lab are to make useful connections between classical arts and academic sciences. She is a contributor and volunteer at the Brain Awareness Week celebrations in Birmingham, Alabama. In her spare time, Mary is a pianist, gardener, and painter.