I think the first general point to make from epidemiological studies across millions of people is the following - that short sleep predicts a shorter life. It predicts all cause mortality.

We know that efficiency and effectiveness are increased when you're getting sufficient sleep, and it will take you longer to do the same thing on an underslept brain, which means you end up having to stay awake longer. So goes the vicious cycle.

Some people actually sleep better when the significant other is with them. For other couples, it's the opposite.

Matthew Walker Quotes