When all this stuff about blue light affecting sleep began I read a number of articles about it and I've read a few more since. The ones from researchers are focused on tablets, not ereaders. At least that's true of the articles I found.
I often read in bed before going to sleep. Sometimes I watch a TV show on a tablet in bed. Sometimes I listen to OTR shows on an MP3 player. I've been doing all this stuff for years and I've never noticed that one affects my sleep more than others. I sleep pretty well.
I don't doubt the research but I do wonder if marketers, who use it to help sell products, attach more importance to it than do the researchers. In any case I'm not sure it applies to ereaders.
If the marketers have their way they'll convince all of you that you can't sleep after reading unless you use their product.
Anyone remember in the 1950s when an aspirin company, I think it was Bayer but I could be wrong, ran ads for a few years that were designed to give people headaches. The FCC, or maybe it was the FTC, finally forced them to stop showing those ads. This isn't quite the same thing but it sure does remind me of that.
Barry