Cecil’s column Why Do We Sleep has several theories on why we sleep.
However, there’s a disease called Fatal Familial Insomnia which is a disease where the person cannot sleep. Over a period of months, their heath deteriorates and they get hallucinations and dementia. From diagnosis to death is 18 months, and it’s always fatal.
From what I understand, it’s a Dominate Gene Prion Disease which doesn’t really make too much sense to me.
There was a BBC documentary on it an NPR story.
I don’t know if the lack of sleep is the cause of the deterioration or a mere symptom, but I’ve heard of sleep deprived people sharing many of the same symptoms. Maybe this disease can help queue us into why we sleep.
By all accounts I have seen, both BSE (“Mad Cow Disease”) and fatal familial insomnia are invariably fatal, totally untreatable, and utterly gruesome. According to the wiki article cited above (and other places I’ve read about it), there isn’t even a good palliative treatment – note that even putting the [del]patient[/del] victim into an induced coma was said not to work. You just suffer horribly for the 6 to 18 months it takes. No wonder people got so hysterical about the BSE scare a few years ago. I say, if you ever get diagnosed with any disease like this, you need to commit suicide as fast as you can, while you still can.
In FFI it may well be lack of sleep that kills.
Mammals kept awake for long periods in experiments will die as they lose weight, their temperature drops and there are a number of hormonal changes.
Barring FFI and experiments though, it’s difficult to get to that point. If kept in a sleep deprived state long enough we periodically black out (“microsleep”), and this will happen even during significant stimulation.
Are there any otherwise healthy vertebrates that don’t sleep? If so, the answer probably lies in the biochemistry of a complex nervous system.
No warm-blooded vertebrate species is known not to sleep. Some cold-blooded species don’t. Makes sense. Warm-blooded metabolisms have a much higher energy budget. But it’s even more interesting than that; apparently, creatures that hibernate apparently have to move up to the sleep state from time to time while hibernating.