Bright daylight linked to earlier sleep and deeper night rest, study finds
A University of Manchester study of 89 adults found that greater exposure to bright, consistent daylight was associated with earlier bedtimes, earlier wake times and more deep sleep in the early night.
Researchers at the University of Manchester reported that adults who spent more time in bright daylight tended to fall asleep and wake up earlier, and they experienced more deep sleep during the first part of the night. The analysis, published in NPJ Biological Timing and Sleep, was based on more than 500 days of data collected from participants who wore light sensors and sleep trackers while keeping daily sleep diaries.
Participants with higher daytime light exposure showed healthier sleep timing and increased early-night deep sleep compared with those receiving less light. The study noted that the relationship is correlational and does not establish causation.
"Light impacts human sleep through a specific pathway, starting with the eye," said Jennifer Martin, Ph.D., a clinical psychologist at Florida International University’s Herbert Wertheim College of Medicine, who was not involved in the research.
"When light hits specific cells in the retina, it communicates to the brain that it’s daytime, meaning we should be alert and active."
Martin added that morning sunlight helps keep the circadian rhythm consistent and recommended spending time outdoors early in the day, limiting bright light in the evening, and maintaining a regular wake-up time. She suggested aiming for at least seven hours of sleep each night and consulting a specialist for chronic sleep problems.
The researchers acknowledged limitations, including the use of wrist-worn devices rather than direct eye exposure measurements and the lack of control for variables such as physical activity or meal timing. Fox News Digital contacted the study authors for comment but did not receive a response.