A study measuring the sleep patterns of students at the 天美影视传媒 has turned up some surprises about how and when our bodies tell us to sleep 鈥� and illustrates the importance of getting outside during the day, even when it鈥檚 cloudy.

Published online Dec. 7 in the Journal of Pineal Research, found that UW students fell asleep later in the evening and woke up later in the morning during 鈥� of all seasons 鈥� winter, when daylight hours on the UW鈥檚 Seattle campus are limited and the skies are notoriously overcast.

The team behind this study believes it has an explanation: The data showed that in winter students received less light exposure during the day. Other research has indicated that getting insufficient light during the day leads to problems at night, when it鈥檚 time for bed.

鈥淥ur bodies have a natural circadian clock that tells us when to go to sleep at night,鈥� said senior author , a UW professor of biology. 鈥淚f you do not get enough exposure to light during the day when the sun is out, that 鈥榙elays鈥� your clock and pushes back the onset of sleep at night.鈥�

The study used wrist monitors to measure sleep patterns and light exposure for 507 UW undergraduate students from 2015 to 2018. Data indicated that students were getting roughly the same amount of sleep each night regardless of season. But, on school days during the winter, students were going to bed on average 35 minutes later and waking up 27 minutes later than summer school days. This finding surprised the team, since Seattle 鈥� a high-latitude city 鈥� receives nearly 16 hours of sunlight on the summer solstice, with plenty evening light for social life, and just over eight hours of sunlight on the winter solstice.

鈥淲e were expecting that in the summer students would be up later due to all the light that鈥檚 available during that season,鈥� said de la Iglesia.

Based on student sleep data, the researchers hypothesized that something in winter was 鈥減ushing back鈥� the students鈥� circadian cycles. For most humans, including college students, the innate circadian cycle governing when we鈥檙e awake and asleep runs at about 24 hours and 20 minutes 鈥� and is 鈥渃alibrated鈥� daily by input from our environment. For UW students in the study, sleep data indicated that their circadian cycles were running up to 40 minutes later in winter compared to summer.

The team focused on light as a potential explanation for this winter delay. But light has different impacts on circadian rhythms at different times of the day.

鈥淟ight during the day 鈥� especially in the morning 鈥� advances your clock, so you get tired earlier in the evening, but light exposure late in the day or early night will delay your clock, pushing back the time that you will feel tired,鈥� said de la Iglesia. 鈥淯ltimately, the time that you fall asleep is a result of the push and pull between these opposite effects of light exposure at different times of the day.鈥�

Data showed that daytime light exposure had a greater impact than evening light exposure in the UW study. Each hour of daytime light 鈥渕oved up鈥� the students鈥� circadian phases by 30 minutes. Even outdoor light exposure on cloudy or overcast winter days in Seattle had this effect, since that light is still significantly brighter than artificial indoor lighting, said de la Iglesia. Each hour of evening light 鈥� light from indoor sources like lamps and computer screens 鈥� delayed circadian phases by an average of 15 minutes.

鈥淚t鈥檚 that push-and-pull effect,鈥� said de la Iglesia. 鈥淎nd what we found here is that since students weren鈥檛 getting enough daytime light exposure in the winter, their circadian clocks were delayed compared to summer.鈥�

The study offers lessons not just for college students.

鈥淢any of us live in cities and towns with lots of artificial light and lifestyles that keep us indoors during the day,鈥� said de la Iglesia. 鈥淲hat this study shows is that we need to get out 鈥� even for a little while and especially in the morning 鈥� to get that natural light exposure. In the evening, minimize screen time and artificial lighting to help us fall asleep.鈥�

Lead author on the paper is , an associate manager with the Allen Institute for Cell Science, who conducted the study as a UW doctoral student. Co-authors are UW undergraduate alum Isabelle Hua, now a researcher at the National Institute of Neurological Disorders and Stroke; Alex Grahe in the UW Department of Biology; Jason Fleischer and Satchidananda Panda of the Salk Institute; Kenneth Wright and C茅line Vetter of the University of Colorado, Boulder; and UW teaching professor of biology Jennifer Doherty. The research was funded by the National Science Foundation. Dunster was supported by the Riddiford-Truman Fellowship and the Hoag Endowed Graduate Fellowship through the UW Department of Biology.

For more information, contact de la Iglesia at horaciod@uw.edu.

In much of the United States, there is a twice-yearly shift in timekeeping between standard time and daylight saving time, or DST, which delays both sunrise and sunset to make mornings darker and evenings brighter. Recently, scientists, policy experts, lawmakers and citizens have debated abandoning the twice-a-year switch and adopting either year-round standard time or DST.

A team of researchers at the 天美影视传媒 鈥� led by postdoctoral researcher Calum Cunningham and , an associate professor of quantitative wildlife sciences 鈥� have found that one of those options would sharply reduce a hazard common to much of the country: deer-vehicle collisions. In a published Nov. 2 in Current Biology, they report that adopting permanent DST in the United States would reduce deer-vehicle collisions and likely prevent an estimated 36,550 deer deaths, 33 human deaths, 2,054 human injuries and $1.19 billion in costs each year. Deer-vehicle collisions would decrease under permanent DST because skies would be brighter later into the evening.

There are an estimated 2.1 million deer-vehicle collisions in the United States each year, killing about 440 people, causing 59,000 injuries and costing upwards of $10 billion.

鈥淲ildlife-vehicle collisions are a huge and growing problem,鈥� said Cunningham. 鈥淭here are social costs 鈥� people killed and injured 鈥� and it鈥檚 also a conservation problem as it鈥檚 one of the largest sources of human-caused mortality of wildlife.鈥�

Cunningham, Prugh and their colleagues analyzed wildlife-vehicle collision data from 23 states. The vast majority of these were collisions involving two widespread species of deer, white-tailed deer that predominate in the eastern U.S. and mule deer, which are more common in the western U.S.

The dataset, which includes more than 1 million deer-vehicle collisions from 1994 to 2021, revealed that the risk of deer-vehicle collision depends on the overlap of both human and deer activity. Deer and related species are crepuscular, meaning they are most active around dawn and dusk. The team found that most collisions occurred in the hours between sunset and sunrise the next morning. Collisions were 14 times more frequent two hours after sunset than two hours before sunset.

The researchers found that deer-vehicle collisions peak in the fall, with nearly 10% occurring during the two-week period around the switch from DST to standard time. The shift itself causes an abrupt increase in the amount of driving after sunset, which corresponded with a 16% increase in deer-vehicle collisions in the week following the time shift.

For ungulates like deer, fall is also the 鈥渞ut,鈥� their mating season, during which their activity level increases by as much as 50%.

鈥淲e believe that this fall spike really happens due to the overlap of these two factors: the breeding season and the change from daylight saving time back to standard time,鈥� said Prugh. 鈥淲e don鈥檛 see a corresponding shift in deer-vehicle collisions in the spring during the other time change, and we believe that鈥檚 in part because spring is not a breeding season for deer.鈥�

The patterns that Cunningham, Prugh and their colleagues found on deer-vehicle collisions allowed them to model collisions under permanent standard time and permanent DST. They estimate an increase of 73,660 deer-vehicle collisions under permanent standard time, with 66 additional human deaths and 4,140 additional injuries, and an added $2.39 billion in collision costs. Permanent DST showed the opposite trend, with a decrease of about 2.3% in deer-vehicle collisions over a full year. Both scenarios would do away with increased accidents caused specifically by the biannual time-shift and the subsequent 鈥渟ocial jetlag鈥� caused by out-of-sync circadian rhythms.

Vehicle collisions are a major source of human-wildlife conflict. Since human societies in modern times tend to live their lives more by clocks than the sun鈥檚 position in the sky, understanding the factors that lead to these collisions could help save lives and prevent injury, Cunningham said.

鈥淗umans today have this 鈥榚vening bias鈥� in our activity: we get up later and stay active later than what the sun is telling us to do,鈥� said Cunningham. 鈥淎s long as people are living their lives 鈥榖y the clock,鈥� which animals do not, people need to be aware of risks and make adjustments where we can. If people are thinking about what they can do for wildlife and for their own lives, reducing driving during dark hours is likely to help significantly. In areas with deer, the risk of harming wildlife and yourself while driving is 14 times higher when it is dark.鈥�

Co-authors on the paper are Tristan Nu帽ez, Yasmine Hentati, Ben Sullender, Catherine Breen, Taylor Ganz, Samantha Kreling, Kayla Shively, Ellie Reese and Jeff Miles, all in the UW School of Environmental and Forest Sciences. Cunningham was funded by the Australian Fulbright Commission.

For more information, contact Cunningham at cxcunn@uw.edu and Prugh at lprugh@uw.edu.

For centuries, humans have blamed the moon for our moods, accidents and even natural disasters. But new research indicates that our planet鈥檚 celestial companion impacts something else entirely 鈥� our sleep.

In a published Jan. 27 in Science Advances, scientists at the 天美影视传媒, the National University of Quilmes in Argentina and Yale University report that sleep cycles in people oscillate during the : In the days leading up to a full moon, people go to sleep later in the evening and sleep for shorter periods of time. The research team, led by UW professor of biology , observed these variations in both the time of sleep onset and the duration of sleep in urban and rural settings 鈥� from Indigenous communities in northern Argentina to college students in Seattle, a city of more than 750,000. They saw the oscillations regardless of an individual鈥檚 access to electricity, though the variations are less pronounced in individuals living in urban environments.

The pattern鈥檚 ubiquity may indicate that our natural circadian rhythms are somehow synchronized with 鈥� or entrained to 鈥� the phases of the lunar cycle.

鈥淲e see a clear lunar modulation of sleep, with sleep decreasing and a later onset of sleep in the days preceding a full moon,鈥� said de la Iglesia. 鈥淎nd although the effect is more robust in communities without access to electricity, the effect is present in communities with electricity, including undergraduates at the 天美影视传媒.鈥�

Using wrist monitors, the team tracked sleep patterns among 98 individuals living in three Toba-Qom Indigenous communities in the Argentine province of Formosa. The communities differed in their access to electricity during the study period: One rural community had no electricity access, a second rural community had only limited access to electricity 鈥� such as a single source of artificial light in dwellings 鈥� while a third community was located in an urban setting and had full access to electricity. For nearly three-quarters of the Toba-Qom participants, researchers collected sleep data for one to two whole lunar cycles.

Past studies by de la Iglesia鈥檚 team and other research groups have shown that access to electricity impacts sleep, which the researchers also saw in their study: Toba-Qom in the urban community went to bed later and slept less than rural participants with limited or no access to electricity.

But study participants in all three communities also showed the same sleep oscillations as the moon progressed through its 29.5-day cycle. Depending on the community, the total amount of sleep varied across the lunar cycle by an average of 46 to 58 minutes, and bedtimes seesawed by around 30 minutes. For all three communities, on average, people had the latest bedtimes and the shortest amount of sleep in the nights three to five days leading up to a full moon.

When they discovered this pattern among the Toba-Qom participants, the team analyzed sleep-monitor data from 464 Seattle-area college students that had been collected for a separate study. They found the same oscillations.

The team confirmed that the evenings leading up to the full moon 鈥� when participants slept the least and went to bed the latest 鈥� have more natural light available after dusk: The waxing moon is increasingly brighter as it progresses toward a full moon, and generally rises in the late afternoon or early evening, placing it high in the sky during the evening after sunset. The latter half of the full moon phase and waning moons also give off significant light, but in the middle of the night, since the moon rises so late in the evening at those points in the lunar cycle.

鈥淲e hypothesize that the patterns we observed are an innate adaptation that allowed our ancestors to take advantage of this natural source of evening light that occurred at a specific time during the lunar cycle,鈥� said lead author , a UW postdoctoral researcher in the Department of Biology.

Whether the moon affects our sleep has been a controversial issue among scientists. Some studies hint at lunar effects only to be contradicted by others. De la Iglesia and Casiraghi believe this study showed a clear pattern in part because the team employed wrist monitors to collect sleep data, as opposed to user-reported sleep diaries or other methods. More importantly, they tracked individuals across lunar cycles, which helped filter out some of the 鈥渘oise鈥� in data caused by individual variations in sleep patterns and major differences in sleep patterns between people with and without access to electricity.

These lunar effects may also explain why access to electricity causes such pronounced changes to our sleep patterns, de la Iglesia added.

鈥淚n general, artificial light disrupts our innate circadian clocks in specific ways: It makes us go to sleep later in the evening; it makes us sleep less. But generally we don鈥檛 use artificial light to 鈥榓dvance鈥� the morning, at least not willingly. Those are the same patterns we observed here with the phases of the moon,鈥� said de la Iglesia.

鈥淎t certain times of the month, the moon is a significant source of light in the evenings, and that would have been clearly evident to our ancestors thousands of years ago,鈥� said Casiraghi.

The team also found a second, 鈥渟emilunar鈥� oscillation of sleep patterns in the Toba-Qom communities, which seemed to modulate the main lunar rhythm with a 15-day cycle around the new and full moon phases. This semilunar effect was smaller and only noticeable in the two rural Toba-Qom communities. Future studies would have to confirm this semilunar effect, which may suggest that these lunar rhythms are due to effects other than from light, such as the moon鈥檚 maximal gravitational 鈥渢ug鈥� on the Earth at the new and full moons, according to Casiraghi.

Regardless, the lunar effect the team discovered will impact sleep research moving forward, the researchers said.

鈥淚n general, there has been a lot of suspicion on the idea that the phases of the moon could affect a behavior such as sleep 鈥� even though in urban settings with high amounts of light pollution, you may not know what the moon phase is unless you go outside or look out the window,鈥� said Casiraghi. 鈥淔uture research should focus on how: Is it acting through our innate circadian clock? Or other signals that affect the timing of sleep? There is a lot to understand about this effect.鈥�

Co-authors are Ignacio Spiousas at the National University of Quilmes; former UW researchers Gideon Dunster and Kaitlyn McGlothlen; and Eduardo Fern谩ndez-Duque and Claudia Valeggia at Yale University. The research was funded by the National Science Foundation and the Leakey Foundation.

For more information, contact de la Iglesia at horaciod@uw.edu and Casiraghi at lcasira@uw.edu.

When Seattle Public Schools that it would reorganize school start times across the district for the fall of 2016, the massive undertaking took more than a year to deploy. Elementary schools started earlier, while most middle and all of the district’s 18 high schools their opening bell almost an hour later 鈥� from 7:50 a.m. to 8:45 a.m. Parents had mixed reactions. Extracurricular activity schedules changed. School buses were redeployed.

And as hoped, teenagers used the extra time to sleep in.

In a published Dec. 12 in the journal , researchers at the 天美影视传媒 and the Salk Institute for Biological Studies announced that teens at two Seattle high schools got more sleep on school nights after start times were pushed later 鈥� a median increase of 34 minutes of sleep each night. This boosted the total amount of sleep on school nights for students from a median of six hours and 50 minutes, under the earlier start time, to seven hours and 24 minutes under the later start time.

“This study shows a significant improvement in the sleep duration of students 鈥� all by delaying school start times so that they’re more in line with the natural wake-up times of adolescents,” said senior and corresponding author , a UW professor of biology.

The study collected light and activity data from subjects using wrist activity monitors 鈥� rather than relying solely on self-reported sleep patterns from subjects, as is often done in sleep studies 鈥� to show that a later school start time benefits adolescents by letting them sleep longer each night. The study also revealed that, after the change in school start time, students did not stay up significantly later: They simply slept in longer, a behavior that scientists say is consistent with the natural biological rhythms of adolescents.

“Research to date has shown that the circadian rhythms of adolescents are simply fundamentally different from those of adults and children,” said lead author , a UW doctoral student in biology.

In humans, the churnings of our circadian rhythms help our minds and bodies maintain an internal “clock” that tells us when it is time to eat, sleep, rest and work on a world that spins once on its axis approximately every 24 hours. Our genes and external cues from the environment, such as sunlight, combine to create and maintain this steady hum of activity. But the onset of puberty lengthens the circadian cycle in adolescents and also decreases the rhythm’s sensitivity to light in the morning. These changes cause teens to fall asleep later each night and wake up later each morning relative to most children and adults.

“To ask a teen to be up and alert at 7:30 a.m. is like asking an adult to be active and alert at 5:30 a.m.,” said de la Iglesia.

Scientists generally recommend that teenagers get eight to 10 hours of sleep each night. But early-morning social obligations 鈥� such as school start times 鈥� force adolescents to either shift their entire sleep schedule earlier on school nights or truncate it. Certain light-emitting devices 鈥� such as smartphones, computers and even lamps with blue-light LED bulbs 鈥� can interfere with circadian rhythms in teens and adults alike, delaying the onset of sleep, de la Iglesia said. According to a of youth released in 2017 by the U.S. Centers for Disease Control and Prevention, only one-quarter of high school age adolescents reported sleeping the minimum recommended eight hours each night.

“All of the studies of adolescent sleep patterns in the United States are showing that the time at which teens generally fall asleep is biologically determined 鈥� but the time at which they wake up is socially determined,” said Dunster. “This has severe consequences for health and well-being, because disrupted circadian rhythms can adversely affect digestion, heart rate, body temperature, immune system function, attention span and mental health.”

The UW study compared the sleep behaviors of two separate groups of sophomores, all enrolled in biology classes at Roosevelt and Franklin high schools. One group of 92 students, drawn from both schools, wore wrist activity monitors all day for two-week periods in the spring of 2016, when school still started at 7:50 a.m. The wrist monitors collected information about light and activity levels every 15 seconds, but no physiological data about the students. In 2017, about seven months after school start times had shifted later, the researchers had a second group of 88 students 鈥� again drawn from both schools 鈥� wear the wrist activity monitors. Researchers used both the light and motion data in the wrist monitors to determine when the students were awake and asleep. Two teachers at Roosevelt and one at Franklin worked with the UW researchers to carry out the study, which was incorporated into the curriculum of the biology classes. Students in both groups also self-reported their sleep data.

The information obtained from the wrist monitors revealed the significant increase in sleep duration, due largely to the effect of sleeping in more on weekdays.

“Thirty-four minutes of extra sleep each night is a huge impact to see from a single intervention,” said de la Iglesia.

The study also revealed other changes beyond additional shut-eye. After the change, the wake-up times for students on weekdays and weekends moved closer together. And their academic performance, at least in the biology course, improved: Final grades were 4.5 percent higher for students who took the class after school start times were pushed back compared with students who took the class when school started earlier. In addition, the number of tardies and first-period absences at Franklin dropped to levels similar to those of Roosevelt students, which showed no difference between pre- and post-change.

The researchers hope that their study will help inform ongoing discussions in education circles about school start times. The American Academy of Pediatrics in 2014 that middle and high schools begin instruction no earlier than 8:30 a.m., though U.S. high schools start the day before then. In 2018, California lawmakers that would ban most high schools from starting class before 8:30 a.m. In 2019, Virginia Beach, home to one of the largest school districts in Virginia, to its school start times.

“School start time has serious implications for how students learn and perform in their education,” said de la Iglesia. “Adolescents are on one schedule. The question is: What schedule will their schools be on?”

Co-authors on the study are Luciano de la Iglesia, Miriam Ben-Hamo and Claire Nave at the UW; and Jason Fleischer and Satchidananda Panda at the Salk Institute in La Jolla, California. The study was funded by the National Science Foundation and the 天美影视传媒.

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For more information, contact de la Iglesia at +1 206-616-4697 or horaciod@uw.edu and Dunster at +1 330-465-4898 or gdunster@uw.edu.

To reach the teachers involved in this study, contact Tim Robinson with Seattle Public Schools at +1 206-252-0203 or tirobinson@seattleschools.org.

For the full article, please visit:

Grant number: 1743364.

While the Ebola outbreak in West Africa has captured the world鈥檚 attention, it’s just one of many emerging infections that we must confront in the coming years, said , UW professor of microbiology. He leads Ebola research at a high-level biocontainment facility at the Rocky Mountain Laboratories in Montana.

“Ebola is not the only emerging virus; it鈥檚 just the most famous one,鈥� Katze said. 鈥淭here鈥檚 West Nile, which was never in North America before and now is everywhere. There鈥檚 Chikungunya virus, which had never been in the Americas, but now has spread through the Caribbean and has reached the southern United States. There鈥檚 SARS (Severe acute respiratory syndrome), which spread from Asia to Toronto and Vancouver, and there鈥檚 MERS (Middle Eastern Respiratory Syndrome) that still ongoing in Saudi Arabia and the Middle East. That epidemic isn鈥檛 over.

To be more agile in responding to emerging pathogens, Katze advocates for accelerated development of new drugs and vaccines.

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As the new school year approaches, School of Nursing sleep expert Teresa Ward, professor of parent and child nursing, offers advice on helping your children arrive rested each day and ready to learn and play.

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