Manchester researchers link brighter daytime light to earlier bedtime and deeper sleep

Scientists at the University of Manchester studied 89 adults who wore light‑sensing and sleep‑tracking devices for over 500 days in real‑world settings. The data showed that higher and more consistent exposure to bright daylight was associated with going to bed earlier, waking up sooner, and spending a greater proportion of the night in deep sleep.

The findings, published in the journal npj Biological Timing and Sleep, highlight the role of daytime illumination in regulating the circadian clock and suggest simple public‑health advice: increase exposure to natural light during the day and reduce bright light before bedtime to improve sleep quality.