Formation and Sleep Ethics

One of the things I have noted in Praying the Pattern and which I will be reworking and expanding (maybe with this research!) in the forthcoming Living our prayer and praying our lives is how choosing bad sleep and rest patterns is choosing to make it more likely that we behave less graciously than we might otherwise. There is research, now, to back that up:

if you don’t get enough sleep, research suggests you are more likely to engage with unethical and deviant behaviour, such as being mean, bullying your fellow employees or falsifying receipts.  -Disrupted sleep article

So, contrary to some medieval asceticism, we should probably not normally be skimping on sleep.
It does, however, make me wonder what the purpose of sleep deprivation regimes was in those medieval regimes. I have the impression (but without researching it further) that it may have had something to do with avoiding sloth; that lying a-bed was seen as sinfully lazy. But I also wonder whether for some at least, there was a sense that we do indeed tend to worse self-censoring and self-checking when we are tired, so the point in that case may have been to push themselves more closely to their limits to make the testing of benevolence etc more real and more frequent, to give more chance to practice.
If that was the case, then I have to say that I wonder whether that is not, in fact, putting God to the test .... more thought needed.