Exposure to blue light at night reduces melatonin levels more than red light in men, but this effect is not statistically significant in women, even though a similar pattern is seen.

Exposure to blue light from LEDs for three hours reduces melatonin levels more than red light in young adults, with melatonin staying low under blue light but recovering under red light.

Exposure to blue light from LEDs at a specific wavelength and brightness for three hours reduces the hormone melatonin in the saliva of healthy adults, and this reduction lasts longer than when exposed to red light at the same brightness.

One hour of red LED light at night temporarily lowers melatonin levels similarly to blue light, but melatonin rebounds after two to three hours, suggesting red light may interfere less with the body's natural sleep-wake cycle over time.

In healthy young guys, better-quality daylight-like LED lights don’t seem to change daily melatonin levels or brain performance like focus and memory — so upgrading light quality might not always boost health or thinking skills.

In healthy adults who have had limited sleep for two nights, exposure to blue light in the morning may shift the timing of melatonin release to occur earlier than when exposed to dawn-like or dim light.