Daylight in the day linked to earlier sleep and deeper night rest, study finds

A University of Manchester-led study tracked 89 adults over more than 500 days and found brighter, more consistent daytime light exposure is associated with earlier sleep onset and wake times, plus deeper sleep early in the night. Morning daylight appears especially beneficial for stabilizing the sleep-wake rhythm. The research used wrist-worn light sensors and sleep trackers, notes that correlation—not causation—exists, and acknowledges limitations like not measuring eye-level light and not accounting for activity or meals. Recommendations include getting morning light, reducing evening brightness, maintaining a regular wake time, and aiming for about seven hours of sleep per night.