There is a lot of research that lack of sleep (under 7 hours, likely 7-9) causes significant problems with memory, working memory, and is directly linked to cancer and Alzheimer's in later years.

In short, it might be feasible in the short term, especially if they have mindless jobs where they can study. I memorized a LOT of vocab during my factory work summers. But it has to be repetitive and mindless for that. I did more thinking at the factory than I did at software jobs.

Anyway, any time anyone says they work 12 hours and study, I don't believe them by default. Once you factor in commuting and maintenance, it's just not realistic...unless you are in a sweatshop dorm, I guess that would save on commuting/grooming/meal prep.

I think it's a combination of youth and dedication that helps people push through such harsh circumstances. There was a time in my life when I would only sleep for 4 hours a day 2am to 6am and I did this for 2 years. Some good things were that I didn't work during the daytime, only studied, and I had access to very good nutrition. If I look back even I marvel at how this is even possible. But I was very young and super passionate back then. Definitely can't do it at this point in my life.

Pretty amazing dedication isn't it?

> I guess when you are living in slave like conditions, you aren't thinking about that.

You guessed it right. And such people generally have(had) no better option. However, the lack of sleep does manifest as an ailment(s) later in life.