Blue light and sleep: night-time light, melatonin and circadian rhythm

Light is also a time signal

Phones, computers and bright home lighting are not only visual tools. Light also helps the body interpret whether it is day or night. Its timing, intensity, duration and spectrum all matter.

Blue light is not the enemy

Short-wavelength light is naturally present in daylight and supports a clear daytime signal. The relevant issue is maintaining a bright, day-like environment late at night.

Circadian rhythm and melatonin

Specialised retinal cells containing melanopsin contribute to non-visual responses to light, including circadian timing, alertness and melatonin regulation. This system is particularly sensitive to the blue-cyan region, although it responds to more than one wavelength.

Practical evening habits

Prioritise daylight during the morning and daytime. In the evening, reduce overall brightness, use warmer lighting, lower screen intensity and avoid relying on one accessory as a complete solution.

Where glasses fit

Blue-light glasses can modify the spectrum reaching the eyes, but the filter and timing must match the intended use. Learn more in our guide to blue-light filtering glasses.