Natural light and the sleep–wake rhythm: a simple daily habit

The circadian clock receives information from the environment, including the light–dark cycle. Bright morning light tends to signal the start of the day, while lower light in the evening supports the transition toward rest. A single exposure cannot guarantee better sleep: regularity, wake time, activity, and evening habits also matter.

After waking: open the curtains, have breakfast near a window, or take a short walk outdoors.

During the day: use daylight for ordinary activities when practical.

In the evening: dim the lighting gradually and avoid very bright light close to bedtime.

Start without a rigid target. A routine you can repeat several days a week is better than an impossible rule. In strong sunlight, protect your eyes according to local guidance and never stare at the sun.

Natural light alone does not correct insomnia, sleep apnoea, excessive sleepiness, or major jet lag. If problems persist, disrupt daytime life, or include loud snoring with breathing pauses, seek professional advice. Do not drive when drowsy.