” Our bodies have a natural circadian clock that informs us when to go to sleep at night,” stated senior author Horacio de la Iglesia, a UW teacher of biology. “If you do not get enough exposure to light throughout the day when the sun is out, that hold-ups your clock and pushes back the onset of sleep during the night.”
An overcast December day on the University of Washington campus in Seattle. Credit: University of Washington
The research study used wrist monitors to measure sleep patterns and light exposure for 507 UW undergraduate students from 2015 to 2018. Data showed that trainees were getting approximately the exact same amount of sleep each night regardless of season. However, on school days throughout the winter season, trainees were going to bed on typical 35 minutes later and getting up 27 minutes later on than summer season school days. This finding amazed the team, considering that Seattle– a high-latitude city– receives nearly 16 hours of sunlight on the summertime solstice, with plenty evening light for social life, and simply over 8 hours of sunshine on the winter solstice.
” We were expecting that in the summertime trainees would be up later on due to all the light thats offered throughout that season,” stated de la Iglesia.
Based on student sleep data, the scientists hypothesized that something in winter season was “pressing back” the students circadian cycles. For many humans, including college students, the innate circadian cycle governing when were awake and sleeping runs at about 24 hours and 20 minutes– and is “adjusted” daily by input from our environment. For UW students in the study, sleep data showed that their circadian cycles were adding to 40 minutes later on in winter compared to summer season.
The group focused on light as a possible description for this winter season hold-up. Light has various impacts on circadian rhythms at different times of the day.
” Light throughout the day– specifically 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 postpone your clock, pressing back the time that you will feel tired,” said de la Iglesia. “Ultimately, the time that you drop off to sleep is a result of the push and pull between these opposite effects of light exposure at different times of the day.”
Information revealed that daytime light direct exposure had a higher effect than night light exposure in the UW research study. Each hour of daytime light “moved up” the trainees circadian stages by 30 minutes. Even outside light exposure on cloudy or overcast winter days in Seattle had this impact, since that light is still considerably brighter than synthetic indoor lighting, stated de la Iglesia. Each hour of night light– light from indoor sources like lamps and computer screens– delayed circadian phases by approximately 15 minutes.
” Its that push-and-pull impact,” stated de la Iglesia. “And what we found here is that because trainees werent getting adequate daytime light exposure in the winter, their circadian clocks were postponed compared to summertime.”
The study provides lessons not just for college students..
” Many of us live in cities and towns with great deals of synthetic light and lifestyles that keep us inside your home during the day,” stated de la Iglesia. “What this research study reveals is that we require to go out– even for a little while and particularly in the morning– to get that natural light direct exposure. At night, decrease screen time and synthetic lighting to assist us go to sleep.”.
Referral: “Daytime light exposure is a strong predictor of seasonal variation in sleep and circadian timing of university trainees” by Gideon P. Dunster, Isabelle Hua, Alex Grahe, Jason G. Fleischer, Satchidananda Panda, Kenneth P. Wright Jr., Céline Vetter, Jennifer H. Doherty and Horacio O. de la Iglesia, 20 November 2022, Journal of Pineal Research.DOI: 10.1111/ jpi.12843.
Lead author on the paper is Gideon Dunster, 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 scientist 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 Céline Vetter of the University of Colorado, Boulder; and UW mentor professor of biology Jennifer Doherty.
Research study shows that getting inadequate light throughout the day leads to problems during the night, when its time for bed.
A study determining the sleep patterns of trainees at the University of Washington has turned up some surprises about how and when our bodies tell us to sleep– and illustrates the importance of getting outdoors throughout the day, even when its cloudy.
Published online on December 7 in the Journal of Pineal Research, the study discovered that UW students dropped off to sleep later on at night and woke up later on in the early morning throughout– of all seasons– winter season, when daylight hours on the UWs Seattle campus are restricted and the skies are notoriously overcast.
The team behind this research study believes it has a description: The information showed that in winter season students received less light exposure throughout the day. Other research has actually shown that getting insufficient light during the day leads to problems in the evening, when its time for bed.
The research study used wrist monitors to measure sleep patterns and light exposure for 507 UW undergraduate students from 2015 to 2018. Data revealed that daytime light exposure had a greater impact than night light exposure in the UW study. Even outside light exposure on overcast or cloudy winter season days in Seattle had this result, because that light is still substantially brighter than artificial indoor lighting, said de la Iglesia. Each hour of evening light– light from indoor sources like lamps and computer system screens– postponed circadian stages by an average of 15 minutes.
” Many of us live in cities and towns with lots of artificial light and way of lives that keep us inside throughout the day,” said de la Iglesia.