Twelve faculty members at the 91̽�� have been elected to the Washington State Academy of Sciences. They are among 36 scientists and educators from across the state July 17 as new members. Election recognizes the new member’s “outstanding record of scientific and technical achievement and willingness to assist the Academy in providing the best available scientific information and technical understanding to inform complex policy decisions in Washington.”��

The 91̽��faculty members were selected by current WSAS members or by their election to national science academies. Eleven were voted on by current WSAS members:��

, professor, Bill & Melinda Gates Chair, and director of the Paul G. ��Allen School for Computer Science & Engineering, for “contributions in data management for data science, big data systems, cloud computing and image/video analytics and leadership in data science education.”��

professor of civil & environmental engineering and of industrial & systems engineering, for “pioneering work in human mobility analysis and infrastructure resilience, which have transformed transportation systems in terms of both demand and supply, and shaped the future directions of transportation systems research on community-based solutions and disaster resilience.”��

Lloyd and Kay Chapman Endowed Chair for Oral Health and associate dean for research in the 91̽��School of Dentistry, and professor in the Department of Health Systems & Population Health, for “leadership in understanding and addressing children’s oral health inequities through community-based socio-behavioral interventions and evidence-based policies.”��

professor of biology, for “internationally recognized leadership in the biology of sleep, including groundbreaking research on molecular and genetic aspects of the brain, human behavioral studies on learning under varied sleep schedules, and contributions that have shaped policy on school schedules and standard time.”��

, the Virginia and Prentice Bloedel professor of physics and of electrical & computer engineering, for “foundational contributions to fundamental and applied research on the optical and spin properties of quantum point defects in crystals and for service and leadership in the quantum community.” ��

, professor and chair of human centered design and engineering, for “award-winning leadership in HCI computing, whose research has advanced health and education technology, influenced policy, and shaped the HCI field of through impactful scholarship, interdisciplinary collaboration and inclusive, real-world technology design.”��

, professor and associate dean for research in the 91̽��School of Social Work, for “contributions to understanding psychosocial and physiological factors that moderate the effectiveness of their interventions and ultimately improve the health of children with abdominal pain disorders.”��

, professor of medicine in the 91̽��School of Medicine and of pharmacy, “for leadership in health economics and cancer research, including work on financial toxicity, cost- effectiveness, and healthcare policy that has influenced national discussions, improved cancer care access, and shaped policies for equitable and sustainable healthcare.” Ramsey is also Director of the Cancer Outcomes Research Program at Fred Hutch.��

, professor of bioengineering and Vice Dean of Research and Graduate Education in the 91̽��School of Medicine, for “national leadership in biomedical research, research policy, and graduate education, including pioneering novel drug delivery approaches for regenerative medicine applications in the nervous system and other tissues such as bone, cartilage, tendon and skin.”��

, Rabinowitz Endowed Professor of Earth and space sciences, for “revolutionizing our understanding of climate change in Antarctica through pioneering ice core extractions under hazardous Antarctic conditions and their subsequent analyses over two decades, and for applying that expertise to advance climate research in Washington State.”��

, professor of pharmaceutics, for “pioneering contributions to pharmaceutical and translational sciences, including groundbreaking research on drug transporters, PBPK modeling and maternal-fetal pharmacology that have helped shaped drug safety policies.”��

The Academy also welcomed new members who were selected by virtue of their election to the National Academies of Science, Engineering or Medicine. Among them is , the Arthur B. McDonald professor of physics and director of the Center for Experimental Nuclear Physics and Astrophysics. Hertzog was elected to the National Academy of Sciences last year. ��

Horacio de la Iglesia, a 91̽��professor of biology and circadian rhythms expert, was a co-author of the paper and is President of the Society for Research on Biological Rhythms.

“We all love to��see the Huskies beat the Ducks, and appreciate the funds that these games bring to��the UW. But, as instructors, we also��know that student athletes always need to��shoulder more than most students,” de la Iglesia said. “More east-west travel and more travel time has increased this load and added a sleep disparity to��it. Proper sleep is critical for health and we can’t let the health��of��our student-athletes get��out��of focus. As a community, it is��our responsibility to��guard their sleep,��which��will not��only protect their health, but will��also��optimize their academic and athletic performance.”

“Cognitive abilities are best in the morning hours, complex hand-eye coordination in early afternoon, and peak muscle performance in late afternoon-early evening,” de la Iglesia added.��“Therefore, the scheduling of events can favor one or the other team.”

A total of 25 experts co-authored the paper, noting that while travel is essential in collegiate athletic programs it inevitably results in disruptions of academic work, poor sleep, and alterations in most other aspects of student life.

“This white paper highlights some of the potential negative health repercussions of the recent college athletic conference re-alignments.��The effects will be particularly challenging for athletes in sports that compete multiple times per week,” said Dr. Russ Van Gelder, professor and chair of the 91̽��Medicine Department of Ophthalmology and a co-author on the paper.��“I hope that affected university administrations recognize these potential repercussions and take appropriate steps to track and mitigate the effects of frequent trans-time zone travel on their students.”

The 91̽��Athletics program already is��looking at efforts to mitigate the effects of additional travel upon its upcoming move to the Big Ten Conference in August 2024.

“We are excited about the future of our athletic department and will continue working to optimize the student-athlete experience. While competition schedules and travel demands are yet to be determined, we have been working to identify high level, transition-related needs especially as it relates to sleep science,” said Michael Dillon, 91̽��Associate Athletic Director for Health and Wellness.��“We are currently identifying a team of consultants, that will be instrumental in working with our existing staff, to guide education initiatives for our student-athletes.��And, as always, we will continue prioritizing mental and physical health, and implementing solutions to benefit the welfare of Washington student-athletes.”

The authors of the paper share recommendations to lessen the impact of jet lag, including creating event schedules that minimize the circadian differentials between the teams. Other methods include preadaptation for several days before travel or allowing sufficient time in the new location to allow circadian adjustment— but they note the latter may prove difficult because it extends the length of each trip.��Both before and after travel, management of exposure to light is important as are a variety of methods to facilitate good sleep.

This article, “The Negative Effects of Travel on Student Athletes Through Sleep and Circadian Disruption”, by H. Craig Heller and others and published in Journal of Biological Rhythms will be free to access and can be read here:

Adapted from the Society for Research on Biological Rhythms .

Contact: Victor Balta at balta@uw.edu.

A study measuring the sleep patterns of students at the 91̽�� has turned up some surprises about how and when our bodies tell us to sleep — and illustrates the importance of getting outside during the day, even when it’s cloudy.

Published online Dec. 7 in the Journal of Pineal Research, found that 91̽��students fell asleep later in the evening and woke up later in the morning during — of all seasons — winter, when daylight hours on the UW’s 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’s time for bed.

“Our bodies have a natural circadian clock that tells us when to go to sleep at night,” said senior author , a 91̽��professor of biology. “If you do not get enough exposure to light during the day when the sun is out, that ‘delays’ your clock and pushes back the onset of sleep at night.”

The study used wrist monitors to measure sleep patterns and light exposure for 507 91̽��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 — a high-latitude city — 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.

“We were expecting that in the summer students would be up later due to all the light that’s available during that season,” said de la Iglesia.

Based on student sleep data, the researchers hypothesized that something in winter was “pushing back” the students’ circadian cycles. For most humans, including college students, the innate circadian cycle governing when we’re awake and asleep runs at about 24 hours and 20 minutes — and is “calibrated” daily by input from our environment. For 91̽��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.

“Light during the day — especially in the morning — 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,” said de la Iglesia. “Ultimately, 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.”

Data showed that daytime light exposure had a greater impact than evening light exposure in the 91̽��study. Each hour of daytime light “moved up” the students’ 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 — light from indoor sources like lamps and computer screens — delayed circadian phases by an average of 15 minutes.

“It’s that push-and-pull effect,” said de la Iglesia. “And what we found here is that since students weren’t getting enough daytime light exposure in the winter, their circadian clocks were delayed compared to summer.”

The study offers lessons not just for college students.

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

Lead author on the paper is , an associate manager with the Allen Institute for Cell Science, who conducted the study as a 91̽��doctoral student. Co-authors are 91̽��undergraduate alum Isabelle Hua, now a researcher at the National Institute of Neurological Disorders and Stroke; Alex Grahe in the 91̽��Department of Biology; Jason Fleischer and Satchidananda Panda of the Salk Institute; Kenneth Wright and Céline Vetter of the University of Colorado, Boulder; and 91̽��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 91̽��Department of Biology.

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

On Sunday, Nov. 7 we switch from daylight saving time to standard time. A 91̽�� expert in circadian rhythms says that’s a good thing.

, a 91̽��biology professor, says that waking up an hour later will expose us to more sunlight in the morning — bright light that helps us wake up and start our day.

Because our bodies want to sync our activity with daylight hours, de la Iglesia says the shift to standard time will be better for most people to get a good night’s sleep, feel more energetic, and perform better at work and at school.��

He recommends soaking up as much sunlight as possible, especially in the morning, and not staying up too late since we tend to extend our days with electric light and devices when it gets dark.

De la Iglesia says time changes can be hard on us, particularly in the spring when a return to daylight saving time sees a measurable bump in car accidents and work injuries as we lose an hour of sleep and find our body clock mismatched with the new, earlier time. Teenagers will have the toughest time waking earlier, as their natural clock tends toward sleeping in later.

He hopes policymakers will move away from daylight saving time so that we stay permanently on standard time.��

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

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

In a published Jan. 27 in Science Advances, scientists at the 91̽��, 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 91̽��professor of biology , observed these variations in both the time of sleep onset and the duration of sleep in urban and rural settings — 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’s access to electricity, though the variations are less pronounced in individuals living in urban environments.

The pattern’s ubiquity may indicate that our natural circadian rhythms are somehow synchronized with — or entrained to — the phases of the lunar cycle.

“We see a clear lunar modulation of sleep, with sleep decreasing and a later onset of sleep in the days preceding a full moon,” said de la Iglesia. “And although the effect is more robust in communities without access to electricity, the effect is present in communities with electricity, including undergraduates at the 91̽��.”

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 — such as a single source of artificial light in dwellings — 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’s 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 — when participants slept the least and went to bed the latest — 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.

“We 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,” said lead author , a 91̽��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 “noise” 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.

“In 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’t use artificial light to ‘advance’ the morning, at least not willingly. Those are the same patterns we observed here with the phases of the moon,” said de la Iglesia.

“At 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,” said Casiraghi.

The team also found a second, “semilunar” 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’s maximal gravitational “tug” 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.

“In general, there has been a lot of suspicion on the idea that the phases of the moon could affect a behavior such as sleep — 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,” said Casiraghi. “Future 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.”

Co-authors are Ignacio Spiousas at the National University of Quilmes; former 91̽��researchers Gideon Dunster and Kaitlyn McGlothlen; and Eduardo Fernández-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.

In a published June 10 in Current Biology, the team reports that a group of students at CU Boulder generally got more sleep after widespread stay-at-home orders and social distancing guidelines were put into place in mid-March.

“Even though we are living through this incredibly stressful time, which is changing our behaviors drastically, we are seeing changes to sleep behaviors that are for the most part positive,” said lead author Ken Wright, a professor of integrative physiology at CU Boulder and director of the university’s Sleep and Chronobiology Laboratory.

The study compared sleep data on CU Boulder students before and after shelter-in-place guidelines were enacted. Wright had already collected sleep data from 139 CU Boulder students for a week from Jan. 29 to Feb. 4 as part of a class project. On March 16, CU Boulder switched to online instruction, and Wright saw an opportunity.

He repeated the week-long survey in the same students from April 22 to 29, and partnered with two sleep researchers at the 91̽��to analyze the data: , a professor of biology, and postdoctoral researcher , who are co-authors on the paper.

The team found that, on average, the students were devoting 30 more minutes per weekday and 24 more minutes per weekend to sleep. Those students who had been skimping on sleep the most before the pandemic saw the greatest improvements, with some sleeping as much as two additional hours each night.

The students also kept more regular sleep and wake times and experienced less “social jetlag,” which is that groggy feeling that occurs when people stay up late and sleep later on the weekends and must resume an earlier schedule on Monday.

After the pandemic began, 92% of students got the minimum seven hours per night of sleep that is recommended by the Centers for Disease Control and Prevention. Typically, only about two-thirds of U.S. college students get that much sleep.

Studies have shown that inadequate sleep is associated with negative health outcomes, such as weakened immune systems that leave people more vulnerable to viral infections and less responsive to vaccines. In addition, irregular sleep and social jetlag can increase the risk of heart disease, obesity, diabetes and mood disorders, according to Wright.

“The fact that a lot of these sleep measures are improving is a good sign,” said Wright.

In addition, compared to February, students in April went to bed about 50 minutes later during the week and 25 minutes later during the weekend and waking up later, too.

“Generally, later sleep timing is associated with poor health outcomes,” said Wright, who advises people to try to shift their sleep-wake cycle earlier by getting bright-light exposure in the morning and dimming the lights two hours before bedtime.

But it’s not clear that the later bedtimes observed in this study are necessarily bad adjustments.

“These associations were observed during ‘normal’ times when people are on tight schedules, usually getting up earlier than what they’d like,” said Casiraghi. “It’s not clear that later bedtimes are negative, per se, particularly if the difference in sleep timing between weekdays and weekends does not change substantially, as it typically happens in college students.”

More research is needed to determine whether similar shifts are occurring among the general public in the United States and, if so, why. De la Iglesia’s team is carrying out additional studies on how social isolation affects sleep health.

Additional co-authors are Sabrina Linton, Dana Withrow, Shannon Lanza, Celine Vetter and Christopher Depner, all at CU Boulder.

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

Adapted from a by Lisa Marshall at CU Boulder.

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 — 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 91̽�� 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 — 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 — 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 91̽��professor of biology.

The study collected light and activity data from subjects using wrist activity monitors — rather than relying solely on self-reported sleep patterns from subjects, as is often done in sleep studies — 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 91̽��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 — such as school start times — force adolescents to either shift their entire sleep schedule earlier on school nights or truncate it. Certain light-emitting devices — such as smartphones, computers and even lamps with blue-light LED bulbs — 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 — 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 91̽��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 — again drawn from both schools — 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 91̽��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 91̽��.

###

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.

New research comparing traditional hunter-gatherer living conditions to a more modern setting shows that access to artificial light and electricity has shortened the amount of sleep humans get each night. The research, this week in the , is the first study to document this relationship in the field.

“Everything we found feeds what we had predicted from laboratory or intervention studies, where researchers manipulate certain aspects of light exposure. But this is the first time we’ve seen this hold true in a natural setting,” said lead author , a 91̽�� biology professor.

The researchers compared two traditionally hunter-gatherer communities that have almost identical ethnic and sociocultural backgrounds, but differ in one key aspect – access to electricity. They wanted to see if, all other factors aside, electricity would impact people’s sleep during an average week in both the summer and winter.

They found this rare scenario in northeastern Argentina, with two Toba/Qom indigenous communities living about 50 kilometers (31 miles) apart. The first has 24-hour free access to electricity and can turn on lights at any time, while the second has no electricity, relying only on natural light.

In their usual daily routines, the community with electricity slept about an hour less than their counterparts with no electricity. These shorter nights were mostly due to people who had the option to turn on lights and go to bed later, the researchers found.

Both communities slept longer in the winter and for fewer hours in the summer.

Though this study took place from 2012 to 2013, the sleep-pattern differences observed between the communities can be seen as an example of how our ancestors likely adapted their sleep behaviors as livelihoods changed and electricity became available, de la Iglesia said.

“In a way, this study presents a proxy of what happened to humanity as we moved from hunting and gathering to agriculture and eventually to our industrialized society,” he said. “All the effects we found are probably an underestimation of what we would see in highly industrialized societies where our access to electricity has tremendously disrupted our sleep.”

The researchers visited each community for a week during the summer and winter, placing bracelets onto the wrist of each study participant to monitor activity. The devices can track slight changes in movement, so a still wrist for a longer time implies that a person is sleeping.

Participants also kept sleep diaries during the study period, where they recorded what times they went to bed and woke up, as well as any naps throughout the day. This information mainly was used to corroborate data collected from the wristbands.

Even in sub-tropical Argentina, where the differences between summer and winter daylight hours vary about two and a half hours at most, study participants naturally slept longer in the winter. In a high-latitude place like Seattle, that daylight difference is close to eight hours between summer and winter.

These findings suggest there’s a biological driver in humans that requires more sleep in the darker winter months.

“We tend to think we’re isolated from seasonal effects even though we know this is the case for many animals,” de la Iglesia said. “I think it’s still embedded in our biology even when we do as much as we can to obscure that difference between summer and winter.”

Past research has shown that artificial light can disrupt our circadian clock and sleep-wake cycle, effectively pushing them back when we turn on the lights in the evening. The researchers have documented this from their observation study, and they plan to look next at whether the later sleep onset and reduced sleep in the community with electricity is due to a shift in the biological clock by measuring melatonin levels in the two communities.

They also plan to study the effects the moon cycle may have on sleep patterns.

Co-authors are Claudia Valeggia and Eduardo Fernández-Duque at Yale University; Diego Golombek at Universidad Nacional de Quilmes in Argentina; Norberto Lanza at Instituto de Investigaciones Geohistóricas in Argentina; and Jeanne Duffy and Charles Czeisler of the Division of Sleep Medicine, Brigham and Women’s Hospital.

The research was funded by the Leakey Foundation, the National Science Foundation and the National Institutes of Health.

###

For more information, contact de la Iglesia at 206-616-4697 or horaciod@uw.edu.

Grant numbers: Leakey Foundation (31266); NSF IOS0909716; NSF Career Award BCS-0952264; NHLBI grant R01HL094654.