Bright daytime light linked to earlier sleep and deeper nighttime rest, study finds
Research involving 89 adults shows that greater exposure to bright daylight is associated with earlier bedtimes, earlier wake times and increased deep sleep during the first part of the night.
A University of Manchester study involving more than 500 days of monitoring of 89 adults found that participants who experienced brighter and more consistent daylight tended to fall asleep and wake up earlier, and recorded more deep sleep in the early night hours. The participants wore wrist-mounted light sensors and sleep trackers while keeping daily sleep diaries, and the results were published in the journal NPJ Biological Timing and Sleep.
"Light impacts human sleep through a specific pathway, starting with the eye," said Jennifer Martin, Ph.D., a clinical psychologist at Florida International University, noting that morning light signals the brain that it is daytime, promoting alertness and a regular sleep-wake cycle.
Martin added that exposure to sunlight early in the day supports a stable sleep routine, while limiting bright light in the evening and keeping a consistent wake-up time can help prevent sleep disturbances. She also recommended at least seven hours of sleep for adults and consultation with a sleep specialist for chronic issues.
The researchers cautioned that the study shows an association, not causation, and acknowledged limitations such as measuring light at the wrist rather than directly at the eye and not accounting for variables like physical activity or meal timing. Fox News Digital contacted the study authors for comment but did not receive a response.