Deep sleep vs light sleep?

[Vojnik]

There were two girls in my courses. Both probably slept very little. A city/party girls (a'la always going). I saw several times as they drink ''Batteries'' (Finland's energy drink) while our lessons. I guess they were more for student parties than studying (''freedom'' ... as living first time alone). Neither of them came back 2. autumn.

That's silly. Girls shouldn't be like that.

[Voskos]

REM phase is usually after 3:00 am from what I've read so far.

[Zeno]

I usually sleep 9-10 hours lately, with the hours of them being deep sleep probably being 5. I cannot wake up at all during these five hours.

[Finnish Swede]

That's silly. Girls shouldn't be like that.

No one should .... humans needs some sleep. If you compensate that partly with energy drinks / coffeine tablets ... you are playing with fire.

[PaleoEuropean]

REM phase is usually after 3:00 am from what I've read so far.

Probably closer to 1 am to 2 am imo if you are going to bed at 10. Everyone is different but we all cycle inbetween REM and the other stages of sleep. We don't go into our deepest stage of sleep until we go through an REM cycle usually. I have noticed that I have two dreaming cycles per night myself one about 2-3 am and another right before I wake up.

[Faklon]

Do these devices use actigraphy based on simple gyroscopes?

I believe it would be inaccurate in terms of measuring actual brain waves.

Not a doctor to know how movement would relate to the frequency and the amplitude of brain signals but the physics seem too simplistic.