Some say that going out in the sun could cause skin issues. Well, if you need a good sleep, you have to be out in the sun. A group of researchers from the University of Washington (UW) in Seattle found that going outdoors more during the day might lead to slipping into sleep more easily during the night.
Published online Dec. 7 in the Journal of Pineal Research, the study found that UW 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.
“Our bodies have a natural circadian clock that tells us when to go to sleep at night,” said senior author Horacio de la Iglesia, a UW 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 involved 507 UW undergraduate students, with data gathered between 2015 and 2018 through wrist monitors. The monitors measured both sleep activity and the participants’ exposure to light.
During the winter, students went to bed an average of 35 minutes later and woke up an average of 27 minutes later than during the summer.
The numbers were somewhat surprising given Seattle’s high latitude; there’s plenty of natural daylight in the summer to make use of for evening activities.
The researchers suggest that light exposure has different impacts on the circadian clock at different times of the day. Light during the day is more likely to cause you to sleep earlier, while light at night – perhaps from artificial sources – will push back that timing, meaning your body isn’t sleepy until later.
Data analysis revealed that each hour of daytime light exposure, even on cloudy days, shifted the students’ circadian phases forward by around 30 minutes. However, each hour of evening light pushed these phases back by about 15 minutes.
This new study shows that light exposure during the day and night has an effect, too, with artificial light playing a role ever since the invention of the electric lightbulb. Our activities are no longer limited by the hours of daylight as they once were.