Spending more time in bright daylight could help individuals fall asleep earlier and achieve deeper sleep at night, according to a new study published in the journal NPJ Biological Timing and Sleep. The research, led by scientists at the University of Manchester, analyzed data from 89 adults over 500 days, utilizing light sensors and sleep trackers alongside daily sleep diaries.
The study found that participants who experienced brighter and more consistent daytime light exposure tended to fall asleep and wake up earlier. These individuals also demonstrated healthier sleep timing and experienced more deep sleep during the initial portion of the night compared to those with less light exposure.
Experts note that light plays a crucial role in regulating the body's internal clock. "Light impacts human sleep through a specific pathway, starting with the eye," explained Jennifer Martin, Ph.D., a clinical psychologist and professor at Florida International University’s Herbert Wertheim College of Medicine, who was not involved in the study. "When light hits specific cells in the retina, it communicates to the brain that it’s daytime, meaning we should be alert and active."
Morning light, in particular, is considered beneficial for maintaining a consistent sleep-wake cycle. "Exposure to sunlight early in the day is really good for healthy sleep," Martin stated. "Regular morning light helps people feel sleepy around the same time each evening and build a strong sleep routine."
Conversely, limiting exposure to bright light in the evening can also enhance sleep quality. Martin advises avoiding bright light in the two hours preceding bedtime and maintaining a consistent wake-up time each morning. "Varying your wake time by more than about one hour can lead to feelings of ‘jet lag’ and contribute to trouble with regularly sleeping well," she added.
While the study highlights a correlation between daytime light exposure and improved sleep patterns, the researchers acknowledged certain limitations. They noted that the observed relationship does not definitively prove causation. Additionally, light exposure was measured using wrist-worn devices rather than directly at the eyes, and the study did not account for other factors that could influence sleep, such as physical activity or meal timing. Adults are generally advised to aim for at least seven hours of sleep per night, seeking professional help if sleep issues become chronic.