It's unfortunate that you're being downvoted without anyone telling you why they're downvoting.

The issue isn't brightness, it's the actual color of the light. The tl;dr version is "blue light definitely messes with your sleep cycle." There's a Wikipedia page about this, with several references at the bottom: https://en.wikipedia.org/wiki/Effects_of_blue_light_technolo... (And I'm sure a search in your favorite search engine will find even more information on this subject)