Question: in what way does sleeping about 4-5 hours a day and going to school affect someone's health or brain?

Joe Bathelt answered on 14 Nov 2016:

That is a great question. According to a recent review that summarised studies that looked at the relationship between sleep and school performance in high school students found that a lot of adolescents do not get enough sleep. The studies also indicated that less sleep and worse quality sleep are related to worse performance at school – worse quality here means more interruptions and less time in deep sleep phases. The studies that manipulated sleep found that disrupting sleep leads to worse performance on memory tests, while increasing sleep duration lead to improvements.

It is has been suggested that the large effect on school performance has to do with the brain regions that sleep deprivation mostly affects. Brain regions at the very fron of the brain (prefrontal cortex) are very important for planning and adjusting behaviour flexibly. These areas were also found to be affected the most by sleep deprivation.

Regarding health, sleep loss increases stress and has been linked to higher risk for long-term illness like heart disease.