INTRODUCTION
Sleep and circadian health affect many outcomes including overall health, mood, cognition, and function. The American Heart Association changed Life’s Simple 7 to Life’s Essential 8 by adding sleep to its heart health measures. The American Academy of Neurology (AAN) acknowledged the importance of sleep at its inaugural Brain Health Summit in 2022. Two public policies, ending seasonal clock change with a transition to permanent Standard Time (ST) and moving middle school and high school start times later, are population-based initiatives to improve sleep health and reduce structural disparities. This article starts with a review of circadian rhythms and how they are impacted by these two policies, followed by a discussion on the effects of Daylight Saving Time (DST) and school start times on health and mood and other broader implications for society (eg, education, work, motor vehicle crashes). The article concludes with a discussion of the current state of these policies.
SLEEP AND CIRCADIAN RHYTHMS
The four elements of healthy sleep are duration, quality, timing, and regularity. The disruption of any of these elements can affect health and function. Circadian rhythms affect all four elements of sleep by helping to anticipate daily changes in the environment. The central clock in the brain sends signals to cells throughout the body to coordinate important functions, such as hormone secretion, heart function, metabolism, digestion, and sleep cycles. Circadian rhythms are also important for controlling cell growth and repair, clearing away toxic substances, and altering brain-cell connections to enhance memory and learning.
Circadian rhythms primarily align to solar time, or the time when the sun is overhead at noon. In order for circadian rhythms to inform cells regarding the time of day, body clocks must align with the 24-hour day. Genetics, age, the timing of sunlight exposure, differences in ambient light levels such as living in the city versus the country, and medications all affect the timing of circadian rhythms. The circadian rhythms of approximately 90% of humans are slightly longer than 24 hours. This can cause the rhythm to delay, or “run slow,” if not reset daily. For most people, sunlight in the morning realigns the body clock back to 24 hours, keeping it in sync with the environment. Exposure to sunlight in the evening has the opposite effect; it delays circadian rhythms, causing the body to run later than 24 hours the next day. Artificial light can have similar effects, but body clocks respond most strongly to sunlight.
CLOCK CHANGES (DAYLIGHT SAVING TIME) AND CIRCADIAN RHYTHMS
People used to set their social clocks according to the position of the sun in the sky (solar time), leading to a 4-minute social clock difference for every 1° of longitude. In 1883, the United States legally established four time zones for the railroad industry. Ideal time zones have a uniform ST for locations with similar longitude. In an ideal time zone, the sun is overhead at noon at the time zone meridian (solar time) and all locations are within 30 minutes for ideal alignment. However, for political and economic reasons, the boundaries of time zones have been manipulated (figure 1a). Locations on the western edges of most US time zones are misaligned from solar time by approximately 1 hour when on ST. The additional 1-hour delay during DST (during which clocks are advanced, an hour is “lost,” and noon becomes 1 pm) increases misalignment with solar time (figure 1b).
A clock time that is later than solar time, due to either DST or misaligned time zones, affects sleep and circadian rhythms in two ways. Because circadian time essentially remains aligned with solar time, the social clock time shifts earlier compared to circadian time, forcing us to wake up before our bodies are ready. Additionally, later sunrises and sunsets shift circadian rhythms and sleep times later, widening the discrepancy between social time and circadian time even more than the 1-hour clock change. The degree of temporal misalignment can be objectively measured by social jet lag. Social jet lag is the difference between sleep timing on days with external influences (school or work days) and free days. Sleep timing on free days is determined by chronotype, which is the preference for sleep timing measured by the midpoint of sleep on free days.
Those with evening chronotypes (night owls) often prefer the later sunsets of DST because they align with their preferred wake time. However, people with evening chronotypes are most likely to be harmed by the loss of morning light in winter and later evening light in summer during DST, resulting in greater social jet lag and greater loss of sleep. This group is also most likely to benefit from the morning light that ST provides as it helps prevent further delay of their body rhythms, especially if school or work starts before 8:30 am because body rhythms can block the ability to fall asleep early enough to get adequate sleep before the required wake time. On the other hand, those with morning chronotypes (morning larks) are typically able to maintain adequate sleep duration and regular sleep patterns without being affected by the social clock.
Evening chronotype is more common in adults than morning chronotype. Teens and young adults are most likely to have later sleep timing. For example, one study found that the average midpoint of sleep on free days peaks shortly before 5 am in 20-year-olds, compared with before 3:30 am after 32 years old. Social jet lag peaks between 10 and 17 years old, presumably due to earlier middle and high school start times.
The seasonal change to and from DST also has acute impacts on circadian rhythms. In the northern hemisphere, the spring switch from ST to DST leads to 1 hour less sleep time as clocks are set forward, which increases the misalignment between social and solar time. The fall switch from DST to ST adds 1 hour of sleep time as clocks are set back and the switch to ST improves the social and circadian alignment. The spring change to DST results in 25 to 60 minutes of average sleep loss in the first days or weeks after the change, but no average sleep is lost after the fall change to ST. However, evidence suggests that many people’s sleep patterns never fully adjust to the later sunrises and sunsets of DST, leading to chronic sleep loss. This sleep loss is influenced by school and work start times. For example, people without children who started work after 8:30 am did not experience sleep loss compared to those with children or who began work before 8:30 am, and those who started work before 7 am were the most affected by sleep loss. Additionally, the amount of social jet lag and the midpoint of sleep shifts later when sunrises and sunsets are later.
LATER SCHOOL START TIMES AND CIRCADIAN RHYTHMS
As noted earlier, adolescents and young adults are more likely to have delayed circadian rhythms, resulting in evening chronotypes. This shift in circadian rhythms occurs with puberty and is related to two forces: a delay in natural melatonin release and a slowing of the buildup of chemicals that contribute to our drive to sleep (eg, adenosine). These forces result in an approximately 2-hour later bedtime. The interaction between social schedule timing and circadian rhythm timing can be used to mitigate some of the negative impacts of circadian misalignment. Later school start times allow naturally sleep-delayed adolescents to sleep later on school days, which can reduce social jet lag, increase average sleep duration, and allow them to better match their body clocks to the social clock.
Teens are especially vulnerable to sleep loss because many middle and high schools start classes early, often before 8 am and some as early as 7 am. These early start times result from societal pressures, including the need to run two consecutive bus schedules, meaning that older children are transported to school followed by younger children, despite their delayed circadian rhythms. Other societal factors include teen availability for after-school childcare and sports programs. When factoring in time for getting ready and transportation to school in the morning, many teens do not get the 8 to 10 hours of sleep that is recommended for optimal health.table 1 shows the relationship between school start times and the percentage of high school students sleeping at least 8 hours per night. When considering circadian rhythms in relation to early school start times, recognizing that students may not be fully alert and ready to learn during first and second periods based on their chronotype is also important.
EVALUATING THE EFFECTS OF TIME POLICY
Most studies of DST evaluate the short-term effects of the spring and fall transitions by comparing periods before and after clock changes. These studies should not be used to determine the long-term impacts of permanent time policy. Instead, several study types provide data to support the expected long-term effects of permanent DST versus permanent ST: studies of natural experiments, position within time zones, and sleep and circadian disruption. Natural experiments compare the same or nearby locations on DST versus ST, such as when the United States tried implementing permanent DST in 1974 or when Russia did so from 2011 to 2014, with other periods. Other opportunities for data collection include when Indiana and Australia adjusted their clock times, or comparing Arizona and Hawaii, which are on permanent ST, with other states. However, few studies have compared the effects throughout all seasons of the year in the same location.
Evaluating Long-Term Effects of Daylight Saving Time
Borisenkov and colleagues provided data from the only year-round natural experiment of permanent DST. The study used self-reported sleep data from school students in northern regions of Russia collected during seasonal DST from 2009 to 2011, permanent DST from 2011 to 2014, and permanent ST from 2015 to 2016. Average weekly sleep duration was the lowest during permanent ST (7.34 ± 1.31 hours) versus permanent DST (7.40 ± 1.21 hours) and seasonal DST (7.69 ± 1.18 hours, P <0.001). The longer duration during DST was due to a larger amount of social jet lag and later rise time during permanent DST. More adolescents (7% to 8%) had 1 to 2 hours and 17% had 2 or more hours of social jet lag during permanent DST than during either seasonal DST or permanent ST. Despite an increase in sleep, permanent DST was associated with an increase in seasonal depression suggesting that, at least in teenagers, quality and alignment of sleep may be more important than average weekly self-reported sleep duration.
Some people believe that the only impact of DST is from the clock transition itself because that is when they notice a sudden change in sleep, alertness, cognition, and mood. One may also think that any chronic sleep loss would be too minimal to have significant impacts. This study highlights how despite no overall changes in weekly average sleep duration during permanent DST, many more adolescents were impacted by a loss of sleep regularity with increases in social jet lag. This study also contradicts a common misconception that mood would improve with more light exposure at the end of the day. Instead, it supports the known connections between mood disorders and light exposure and circadian misalignment, namely, that morning light improves mood and evening light and more delayed circadian rhythms can worsen depression and other mental health disorders.
A second way to study the long-term effects of later clock time is to compare locations within the same time zone that have different sunrise and sunset times. By comparing westerly to easterly locations that have a 1-hour difference in clock time, estimates of the effect of the 1-hour difference between DST and ST clock times can be made. Other methods for studying the effect of clock misalignment include linearly adjusting for distance from the time zone meridian or comparing locations with a sun time more or less than 30 minutes from the time zone meridian. Because DST increases the percentage of people with social jet lag and evening chronotype, studying the outcomes associated with these markers of delayed circadian rhythms is also informative about the impacts of DST. Data from later school start time studies can also support the importance of improved social and circadian alignment.
EFFECTS OF DAYLIGHT SAVING TIME ON HEALTH AND PERFORMANCE
In the days after the spring clock change from ST to DST, studies have found an increased risk of atrial fibrillation, heart attacks, depression, suicide attempts, emergency department visits, failure of in vitro fertilization, mortality, and stroke. Missed medical appointments and medical errors also increase after the ST-to-DST transition and may impact health. When clocks transition back to ST in the fall, most of these negative effects on health are not seen. Position-in-time-zone studies have provided the most data on the long-term effects of later sunrises and sunsets, showing increased risks of obesity, diabetes, cardiovascular disease, and some cancers.
Giuntella and colleagues evaluated the effect of position in a time zone on health and workplace productivity outcomes. They found that 1-hour later sunrise and sunset times were associated with a 10% increased risk of obesity, a 19% increased risk of heart attack, a 16% increased risk of heart disease, and a 5% increased risk of type 2 diabetes. This study estimated that the increased risks of these problems alone would lead to over $2.3 billion per year in increased health care expenses if permanent DST were adopted. Additionally, they estimated 4.4 million days of lost work productivity costing over $600 million annually in the United States. They also found that wages were 3% lower on the western edges of time zones.
Many of the strongest arguments for permanent DST are the benefits to the economy from an increase in retail and recreational activities, especially in the fall and spring when sunsets are later during DST. What the economic evaluation often overlooks is the effects on the overall workforce. This study found that DST would decrease worker productivity due to tardiness or absences and increased health problems, while other studies showed that sleep and circadian disruption lead to billions of dollars of productivity losses; affect concentration, memory formation, and decision making; lead to increases in surfing the internet at work (cyberloafing) and workplace injuries; and decreases in academic performance.
EFFECTS OF DAYLIGHT SAVING TIME ON SOCIETY
The alleged benefits of DST on society derive from the shift of light from before typical work and school time to after, allowing more time for recreational and economic activities as well as a reduction in energy costs for electrical lighting. The overall long-term impacts of DST balance the positive effects of later evening light on activity and safety and the negative effects of later light exposure on sleep and circadian disruption and loss of morning light. The short-term effects of the sudden shifts in clock time in the spring and fall on societal outcomes (table 2) do not necessarily predict the long-term effects of permanent DST or ST.
Some outcomes, such as reductions in crime and energy use and an increase in consumer sales, that may see a short-term boost with more evening light in the spring and fall may have the opposite effect in the winter and summer for several reasons. First, the circadian impacts of later sunrises and sunsets are more likely to be harmful in the winter and summer at the extremes of the photoperiod (day length). If permanent DST were enacted, sunrise would occur after 8 am for 2 to 4 months in the United States (table 3 and figure 2), depriving most people of critical morning light needed for optimizing alertness, cognitive function, reaction time, and decision making, with negative effects on productivity and safety outcomes. Second, the potential benefits of later sunrises and sunsets on recreational activity, energy use, and spending may be mitigated by heat in the summer and cold in the winter. The effects of DST can be modulated by latitude, climate, and culture. For example, after the shift to DST, a short-term increase in children’s daily physical activity was seen in Northern Europe, but no statistical change was seen in the United States and a decrease was seen in Brazil.
Some of the short-term economic boosts may not be considered favorable by the public. A short-term study by JP Morgan compared Los Angeles, California, before and after time changes to Phoenix, Arizona, which remains on permanent ST. The study found that Los Angelenos had relatively higher credit card spending on retail purchases during DST; however, utility bills, gasoline, and health care expenditures also increased during DST. This finding is consistent with another study in Indiana that found 1% higher residential energy bills during seasonal DST compared to permanent ST primarily due to increased heating and air conditioning use during DST.
Long-term, year-round energy data are limited. Although small overall energy savings were seen in the US Department of Energy studies of permanent DST in 1974 and extended DST (when DST was extended from April–October to March–November) in 2007, these data may not reflect current energy consumption. First, lighting has become more energy efficient. Second, the use of heating, air conditioning, and electronics has increased. Finally, the 1974 data may have been impacted by energy restrictions in place during the oil crisis. Year-round studies comparing Arizona to locations with similar climates would help establish whether DST contributes to increased energy consumption between spring and fall but would not reflect changes in winter when both already use ST or reflect heating costs in colder locations.
Long-Term Effects of Later Sunrise and Sunset on Safety
Gentry and colleagues compared 12 years of fatal motor vehicle crashes in the United States for those located in their ideal time zone (within 30 minutes or 7.5° of the time zone meridian) with eccentric locations of more than 30 minutes delay from solar time (figure 3). They found that eccentric regions had 20.8% more fatal motor vehicle crashes. This study highlights the importance for locations to be in their appropriate time zone as well as remain on ST.
LATER SCHOOL START TIMES
School start times impact students, parents, and teachers. Later school start times show improved sleep duration and regularity and multiple outcomes including health, mood disorders, behavior problems, brain development, academics, delinquency, risk-taking behavior, judgment, and decision-making ability. Students with later school start times have extended sleep duration; increased alertness and performance; improved physical and mental health, learning, attendance, graduation rates, and overall well-being; and fewer car crashes. While a common concern about adopting later school start times is the impact on afterschool activities including sports, beneficial effects of sleep on sports performance and a reduction of sports-related injuries in adolescents have been found in some school districts even if practice times are shorter.
Moving elementary school times earlier does not impact outcomes, which is important because of the busing demands of moving middle and high school start times later. Older adolescents and young adults are also affected by the earlier start times of their college classes, with shorter sleep duration and lower grades. A separate study showed that college students who got less sleep had lower grades.
Effect of Later School Start Times on Sleep, Academics, Safety, and Mental Health
Wahlstrom evaluated over 9000 students at eight public high schools in three states by comparing school start times over 3 years. Later school start times allowed more than 60% of students to obtain at least 8 hours of sleep on school nights. Students with school start times of 8:35 am or later had higher grades, better state and national achievement test performance, higher attendance rates, and less tardiness. The study also found that car crashes involving teen drivers decreased by 70% when one school shifted its start times from 7:35 am to 8:55 am. Finally, they found that students getting less than 8 hours of sleep were more likely to have depression symptoms, use caffeine more often, and use illicit drugs, cigarettes, and alcohol.
In general, the literature provides strong evidence that middle and high school start times after 8:30 am are associated with improvements in sleep, attention, mood, and academic outcomes, and reductions in absences, tardiness, and risk-taking behaviors, all of which led the American Academy of Pediatrics, American Association of Sleep Medicine, and others to endorse later school start times. Another study performed in a school district with very early middle and high school start times (7:20 am) found associations between short sleep duration and feeling hopeless, suicidal ideation, suicide attempts, and substance use.
INTERACTION BETWEEN LATER SCHOOL START TIMES AND DAYLIGHT SAVING TIME
Given the benefits of later school start times, some have suggested the switch to permanent DST, moving work and school times later. While this solution would help mitigate the adverse effects of DST, later sunsets and sunrises shift the circadian rhythms of people with evening chronotype by more than 1 hour (increasing social jet lag), so ST provides the best overall circadian alignment. Additionally, moving work and school later would remove the benefit of more time at the end of the day in the sunlight, which is a main argument for DST. On the other hand, the combination of permanent ST and later school start times would allow students to have the best alignment between their circadian rhythms and social schedule.
DAYLIGHT SAVING TIME, SCHOOL START TIMES, AND SLEEP HEALTH DISPARITIES
Public health policies are often used to help lessen the effect of structural disparities. As discussed earlier, social factors such as work and school start times impact the sleep and circadian disruption caused by later sunrises and sunsets and early school or work start times.
Two studies illustrate how permanent ST and later school start times can help mitigate sleep health disparities. Gaski and colleagues evaluated mean Scholastic Aptitude Test (SAT) scores from 350 Indiana public high schools over a 10-year period (1997 to 2006) by comparing regions that followed seasonal DST with those on permanent ST. Mean SAT scores were 16 points lower on average in seasonal DST regions compared with ST regions. This effect was modulated by income, with students from the lowest-income families having the largest drop in scores. Edwards used data on all middle school students in Wake County, North Carolina from 1999 to 2006 to identify the causal effect of daily start times on academic performance. During this time, the school population grew from 20,530 students enrolled in 22 middle schools to 27,686 students enrolled in 28 middle schools, with many schools changing to earlier or later start times. Later-starting students had higher test scores in math and reading. This increase in test scores was attributed to increased sleep, as well as factors such as fewer absences and more time at home with their parents (eg, potentially more time doing homework and less time watching television). The effect of later start times had the strongest impact on students with test scores on the lower end of the distribution (using a quartile regression model).
These studies highlight the structural disparities associated with sleep health public policies. The importance of socioeconomic status as a structural determinant of sleep health and its association with racial disparities in sleep are becoming increasingly clear. A study of late adolescents, for example, found that socioeconomic status was a moderator of the relationship between sleep and developmental outcomes. Sleep disparities may influence some health disparities; one example was a 50% higher rate of liver cancer in non-Hispanic Black people and non-Hispanic Asian, Pacific Islander, American Indian, and Alaskan Native people exposed to later sunrise and sunset times.
The effect of misaligned clock time may be even greater in developing countries. A non-peer-reviewed study evaluating 3 million people in developing countries also found that children from lower-income families were less likely to complete primary and middle school if they were exposed to later sunrises and sunsets such as one would experience on permanent DST. Over the course of a child’s education, the later sun times were associated with an average of 9 fewer months of schooling.
PERMANENT STANDARD TIME ADVOCACY
Over the last decade, action at the local, state, and national levels in support of ending time change and moving school start times later has increased. Approximately 70% of people want to end seasonal clock changes. About 60% of the world uses permanent ST, with Mexico being the most recent country to adopt it in 2022. On the other hand, despite several countries briefly adopting permanent DST, including the United States (twice, most recently in 1974), it has always been abandoned. Before the 1966 Uniform Time Act, states independently decided on time policy, which caused issues with communication, economics, and transportation.
Prior to position statements from the Society of Research in Biological Rhythms (2019) and the American Academy of Sleep Medicine (2020) in support of permanent ST, about 15 states passed legislation that would enact permanent DST if allowed by the federal government, as it is currently federally prohibited. Most of these bills were passed without discussion of the health implications. In March 2022, the US Senate passed the Sunshine Protection Act which, if enacted, would require all states except Arizona and Hawaii to adopt permanent DST; however, it failed to pass the US House of Representatives. The act was reintroduced in 2023. With increasing action from Save Standard Time, a nonprofit organization supporting permanent ST, and over 90 scientific and medical societies (including recent endorsements by the American Medical Association, the AAN, and the Sleep Research Society) and religious and educational organizations, more state-level bills for permanent DST have failed to pass and more permanent ST bills have been sponsored. While a federal bill would be preferable to reduce economic and transportation confusion, the passage of state bills, even if they are contingent on similar legislation in nearby states, is important to show support for permanent ST given the state-level permanent DST bills that have previously passed.
LATER SCHOOL START TIME ADVOCACY
Later school start time advocacy to start middle and high schools no earlier than 8:30 am has primarily occurred on a local level with individual schools or school districts often led by Start School Later chapters which, as of May 2023, are active in four countries, 33 states, and Washington, DC. However, state and federal governments can still have an important role. In 2022, California became the first state to mandate that high schools start no earlier than 8:30 am for most communities followed by Florida in 2023. These larger-scale mandates are important because they help ensure that structural disparities are improved for all children. They also help mitigate some of the concerns about later school start times, including aligning after-school sports. The most successful communities have involved all stakeholders as changes to before-school and after-school care and activities are needed if work schedules do not also shift.
CONCLUSION
Permanent ST and later school start times are public health measures that can lead to widespread benefits to sleep and circadian health. Improvements in circadian alignment and sleep duration will benefit a range of health outcomes. Both advocacy efforts are an opportunity to engage and educate the public on the science and importance of sleep health and circadian rhythms in daily life.
KEY POINTS
- The four elements of healthy sleep are duration, quality, timing, and regularity.
- Circadian rhythms primarily align to solar time, or the time when the sun is overhead at noon.
- Social jet lag is the difference between sleep timing on school or workdays and free days.
- Chronotype, or preference for sleep timing, is measured by the midpoint of sleep on free days.
- Social jet lag is greatest between ages 10 and 17 years.
- The spring clock transition from Standard Time to Daylight Saving Time is associated with more negative effects than the fall transition from Daylight Saving Time to Standard Time.
- Short-term effects of clock transitions do not equate to the long-term effects of permanent Daylight Saving Time or permanent Standard Time.
- Seasonal depression rates are highest during permanent Daylight Saving Time and lowest during permanent Standard Time.
- Motor vehicle crash rates are higher in locations with later sunrises and sunsets.
- Later school start times are associated with higher attendance, higher grades, and better test scores.
- The American Academy of Neurology (AAN) and over 90 medical, scientific, safety, education, and religious groups have endorsed permanent Standard Time.
- Middle schools and high schools should start classes after 8:30 am.
USEFUL WEBSITES
SAVE STANDARD TIME
This website includes information about the effects of Daylight Saving Time, charts to determine sunrise and sunset times, a list of endorsements, and other information and links to assist with advocacy.
savestandardtime.com
THE SCIENCE OF CLOCK CHANGE
A series of 12 short educational videos on the history and effects of time change, hosted by Save Standard Time.
youtube.com/@SaveStandard
START SCHOOL LATER
This website has a comprehensive list of resources for learning about and advocating for later school start times.
startschoollater.net
TAKE ACTION
Send prewritten emails to state and federal legislators, using the forms available from the American Academy of Sleep Medicine or resistbot by texting SST to 50409.
aasm.org/advocacy/take-action
REFERENCES
1. American Heart Association. Life’s Essential 8
TM - How to Get Healthy Sleep Fact Sheet. Published online 2022.
https://www.heart.org/en/healthy-living/healthy-lifestyle/lifes-essential-8/how-to-get-healthy-sleep-fact-sheet
2. Mitchell J, Gillette M. Physiology of the Mammalian Circadian System. In: Principles and Practice of Sleep Medicine. 7th ed. Elsevier; 2022.
3. Czeisler CA, Duffy JF, Shanahan TL, et al. Stability, precision, and near-24-hour period of the human circadian pacemaker. Science 1999;284(5423):2177–2181. doi:10.1126/science.284.5423.2177
4. Hadlow NC, Brown S, Wardrop R, Henley D. The effects of season, daylight saving and time of sunrise on serum cortisol in a large population. Chronobiol Int 2014;31(2):243–251. doi:10.3109/07420528.2013.844162
5. Fischer D, Lombardi DA, Marucci-Wellman H, Roenneberg T. Chronotypes in the US - Influence of age and sex. PLoS One 2017;12(6):e0178782. doi:10.1371/journal.pone.0178782
6. Roenneberg T, Pilz LK, Zerbini G, Winnebeck EC. Chronotype and Social social jetlag: a (self-) critical review. Biology (Basel) 2019;8(3):54. doi:10.3390/biology8030054
7. Johnson KG, Malow BA. Daylight Saving Time: neurological and neuropsychological implications. Curr Sleep Medicine Rep 2022;8(4):86–96. doi:10.1007/s40675-022-00229-2
8. Giuntella O, Mazzonna F. Sunset time and the economic effects of social jetlag: evidence from US time zone borders. J Health Econ 2019;65:210–226. doi:10.1016/j.jhealeco.2019.03.007
9. Borisenkov MF, Tserne TA, Panev AS, et al. Seven-year survey of sleep timing in Russian children and adolescents: chronic 1-h forward transition of social clock is associated with increased social jetlag and winter pattern of mood seasonality. Biological Rhythm Research 2017;48(1):3–12. doi:10.1080/09291016.2016.1223778
10. Fischer D, Lombardi DA. Chronotypes in the US: Influence of longitude position in a time zone. Chronobiol Int 2022;39(3):460–464. doi:10.1080/07420528.2021.2002889
11. Carskadon MA, Acebo C, Jenni OG. Regulation of adolescent sleep: implications for behavior. Ann N Y Acad Sci 2004;1021:276–291. doi:10.1196/annals.1308.032
12. Paruthi S, Brooks LJ, D ’Ambrosio Carolyn, et al. Recommended amount of sleep for pediatric populations: a consensus statement of the American Academy of Sleep Medicine. Journal of Clinical Sleep Medicine 12(06):785–786. doi:10.5664/jcsm.5866
13. Wahlstrom K, Dretzke B, Gordon M, et al. Examining the impact of later high school start times on the health and academic performance of high school students: a multi-site study; 2014. Accessed June 1, 2023.
http://conservancy.umn.edu/handle/11299/162769
14. Foster RG, Peirson SN, Wulff K, et al. Sleep and circadian rhythm disruption in social jetlag and mental illness. Prog Mol Biol Transl Sci 2013;119:325–346. doi:10.1016/B978-0-12-396971-2.00011-7
15. Ziporyn TD, Owens JA, Wahlstrom KL, et al. Adolescent sleep health and school start times: Setting the research agenda for California and beyond. A research summit summary. Sleep Health 2022;8(1):11–22. doi:10.1016/j.sleh.2021.10.008
16. Rishi MA, Ahmed O, Barrantes PJH, et al. Daylight saving time: an American Academy of Sleep Medicine position statement. Journal of Clinical Sleep Medicine 16(10):1781–1784. doi:10.5664/jcsm.8780
17. Liu C, Politch JA, Cullerton E, et al. Impact of daylight savings time on spontaneous pregnancy loss in in vitro fertilization patients. Chronobiol Int 2017;34(5):571–577. doi:10.1080/07420528.2017.1279173
18. Kolla BP, Coombes BJ, Morgenthaler TI, Mansukhani MP. Increased patient safety-related incidents following the transition into Daylight Savings Time. J Gen Intern Med 2021;36(1):51–54. doi:10.1007/s11606-020-06090-9
19. Ellis DA, Luther K, Jenkins R. Missed medical appointments during shifts to and from daylight saving time. Chronobiol Int 2018;35(4):584–588. doi:10.1080/07420528.2017.1417313
20. Manfredini R, Fabbian F, Cappadona R, et al. Daylight Saving Time and acute myocardial infarction: a meta-analysis. J Clin Med 2019;8(3):404. doi:10.3390/jcm8030404
21. Gu F, Xu S, Devesa SS, et al. Longitude position in a time zone and cancer risk in the United States. Cancer Epidemiol Biomarkers Prev 2017;26(8):1306–1311. doi:10.1158/1055-9965.EPI-16-1029
22. VoPham T, Weaver MD, Vetter C, et al. Circadian misalignment and hepatocellular carcinoma incidence in the United States. Cancer Epidemiol Biomarkers Prev 2018;27(7):719–727. doi:10.1158/1055-9965.EPI-17-1052
23. Hafner M, Stepanek M, Taylor J, Troxel WM, van Stolk C. Why sleep matters-the economic costs of insufficient sleep: a cross-country comparative analysis. Rand Health Q 2017;6(4):11.
24. Harrison Y, Horne JA. The impact of sleep deprivation on decision making: a review. J Exp Psychol Appl 2000;6(3):236–249. doi:10.1037//1076-898x.6.3.236
25. Wagner DT, Barnes CM, Lim VKG, Ferris DL. Lost sleep and cyberloafing: Evidence from the laboratory and a daylight saving time quasi-experiment. J Appl Psychol 2012;97(5):1068–1076. doi:10.1037/a0027557
26. Uehli K, Mehta AJ, Miedinger D, et al. Sleep problems and work injuries: a systematic review and meta-analysis. Sleep Med Rev 2014;18(1):61–73. doi:10.1016/j.smrv.2013.01.004
27. Gomez Fonseca A, Genzel L. Sleep and academic performance: considering amount, quality and timing. Current Opinion in Behavioral Sciences 2020;33:65–71. doi:10.1016/j.cobeha.2019.12.008
28. Kamstra MJ, Kramer LA, Levi MD. Losing sleep at the market: the daylight saving anomaly. American Economic Review 2000;90:1005–1011. doi:10.1257/aer.90.4.1005
29. Barnes CM, Wagner DT. Changing to daylight saving time cuts into sleep and increases workplace injuries. J Appl Psychol 2009;94:1305–1371. doi:10.1037/a0015320
30. Fritz J, VoPham T, Wright KP Jr., Vetter C. A chronobiological evaluation of the acute effects of Daylight Saving Time on traffic accident risk. Curr Biol 2020;30:729–735.e2. doi:10.1016/j.cub.2019.12.045
31. Smith AC. Spring forward at your own eisk: Daylight Saving Time and fatal vehicle crashes. American Economic Journal: Applied Economics 2016;8:65–91. doi:10.1257/app.20140100
32. O'Connor PJ, Kancheva M. Marathon run performance on daylight savings time transition days: results from a natural experiment. Chronobiol Int 2022;39:151–157. doi:10.1080/07420528.2021.1974471
33. Doleac JL, Sanders NJ. Under the cover of darkness: how ambient light influences criminal activity. The Review of Economics and Statistics 2015;97(5):1093–1103. doi:10.1162/REST_a_00547
34. Impact of extended Daylight Saving Time on national energy consumption, report to Congress. Energy.gov. Accessed June 1, 2023.
https://www.energy.gov/eere/analysis/impact-extended-daylight-saving-time-national-energy-consumption-report-congress
35. Farrell D, Narasiman V, Ward M. Shedding light on Daylight Saving Time. Published online November 3, 2016. doi:10.2139/ssrn.2966170
36. Goodman A, Page AS, Cooper AR; International Children’s Accelerometry Database (ICAD) Collaborators. Daylight saving time as a potential public health intervention: an observational study of evening daylight and objectively-measured physical activity among 23,000 children from 9 countries. Int J Behav Nutr Phys Act 2014;11:84. doi:10.1186/1479-5868-11-84
37. Kotchen MJ, Grant LE. Does Daylight Saving Time save energy? Evidence from a natural experiment in Indiana. The Review of Economics and Statistics 2011;93(4):1172–1185.
38. U.S. Dept. of Transportation, Office of the Assistant Secretary for Policy, Plans and International Affairs. The daylight saving time study : a report to Congress from the Secretary of Transportation. Published online July 1975.
39. Gentry J, Evaniuck J, Suriyamongkol T, Mali I. Living in the wrong time zone: Elevated risk of traffic fatalities in eccentric time localities. Time & Society 2022;31(4):457–479. doi:10.1177/0961463X221104675
40. Meltzer LJ, Wahlstrom KL, Plog AE, McNally J. Impact of changing school start times on parent sleep. Sleep Health 2022;8(1):130–134. doi:10.1016/j.sleh.2021.08.003
41. Wahlstrom KL, Plog AE, McNally J, Meltzer LJ. Impact of changing school start times on teacher sleep health and daytime functioning. J Sch Health 2023;93(2):128–134. doi:10.1111/josh.13254
42. Adolescent Sleep Working Group, Committee on Adolescence, Council on School Health. School start times for adolescents. Pediatrics 2014;134(3):642–649. doi:10.1542/peds.2014-1697
43. Milewski MD, Skaggs DL, Bishop GA, et al. Chronic lack of sleep is associated with increased sports injuries in adolescent athletes. J Pediatr Orthop 2014;34(2):129–133. doi:10.1097/BPO.0000000000000151
45. Bastian KC, Fuller, SC. Early birds in elementary school? School start times and outcomes for younger students. 2022. Accessed June 1, 2023.
https://journals.sagepub.com/doi/10.3102/01623737221121799
46. Yeo SC, Lai CKY, Tan J, et al. Early morning university classes are associated with impaired sleep and academic performance. Nat Hum Behav 2023;7(4):502–514. doi:10.1038/s41562-023-01531-x
47. Creswell JD, Tumminia MJ, Price S, et al. Nightly sleep duration predicts grade point average in the first year of college. Proc Natl Acad Sci U S A 2023;120(8):e2209123120. doi:10.1073/pnas.2209123120
48. Watson NF, Martin JL, Wise MS, et al. Delaying middle school and high school start times promotes student health and performance: an American Academy of Sleep Medicine position statement. J Clin Sleep Med 2017;13(4):623–625. doi:10.5664/jcsm.6558
49. Winsler A, Deutsch A, Vorona RD, Payne PA, Szklo-Coxe M. Sleepless in Fairfax: the difference one more hour of sleep can make for teen hopelessness, suicidal ideation, and substance use. J Youth Adolesc 2015;44(2):362–378. doi:10.1007/s10964-014-0170-3
50. Gaski JF, Sagarin J. Detrimental effects of daylight-saving time on SAT scores. Journal of Neuroscience, Psychology, and Economics 2011;4:44–53. doi:10.1037/a0020118
51. Edwards F. Early to rise? The effect of daily start times on academic performance. Economics of Education Review 2012;31(6):970–983.
52. El-Sheikh M, Shimizu M, Philbrook LE, Erath SA, Buckhalt JA. Sleep and development in adolescence in the context of socioeconomic disadvantage. J Adolesc 2020;83:1–11. doi:10.1016/j.adolescence.2020.06.006
53. Grandner MA, Williams NJ, Knutson KL, Roberts D, Jean-Louis G. Sleep disparity, race/ethnicity, and socioeconomic position. SleepMed 2016;18:7–18. doi:10.1016/j.sleep.2015.01.020
55. AP-NORC Center for Public Affairs Research. Dislike for changing the clocks persists. 2021
apnorc.org/projects/dislike-for-changing-the-clocks-persists.
56. Roenneberg T, Wirz-Justice A, Skene DJ, et al. Why should we abolish Daylight Saving Time? J Biol Rhythms 2019;34(3):227–230. doi:10.1177/0748730419854197
57. American Medical Association. AMA calls for permanent standard time. Published November 15, 2022. Accessed June 1, 2023.
https://www.ama-assn.org/press-center/press-releases/ama-calls-permanent-standard-time
58. Malow BA. It is time to abolish the clock change and adopt permanent standard time in the United States: a Sleep Research Society position statement. Sleep 2022;45(12):zsac236. doi:10.1093/sleep/zsac236
