Brighter daytime light linked to earlier, deeper sleep, study finds

A Manchester-led study of 89 adults using light sensors and sleep trackers over more than 500 days found that brighter and more consistent daytime light exposure is associated with falling asleep earlier, waking earlier, and experiencing deeper sleep in the first part of the night. Morning light is particularly beneficial for maintaining a steady sleep-wake cycle; reducing bright light in the evening and keeping a consistent wake time may improve sleep. The study shows association, not causation, and used wrist-worn light measurements, with other factors like activity or meals not fully accounted for.