An interesting fact: Sleep, like death, is one of those things that animals do (humans included, of course), for which we have no reasonable explanation.
On so many levels, sleep doesn't make sense. It leaves us vulnerable to attack; it puts us into a non-productive state for almost a third of our lives and renders us effectively paralysed for eight hours out of every twenty-four.
If there were a Top Trumps pack called "Top Trumps - Evolutionary Traits." you would, quite understandably, want to avoid being dealt any card that displayed "Sleep - 8 Hours" as one of its attributes. It sounds like a species extinction just waiting to happen.
However, in very recent years, we have begun to understand more about our need to sleep and what happens when we do.
There's possibly a touch of spring cleaning going on as toxic debris is cleared and filtered out of the cells.
There may also be a bit of organisation, filing and refiling of experiences and memories.
It's also thought that sleep may help us process our emotions, that dreams play a part in that process, and that we would spend most of our lives on the cusp of mental breakdown without that nightly purge.
Although we don't know much about what happens when we do sleep, we certainly know what happens if we don't. Like air, water and food, go without sleep for too long, and we die.
But even there, we're still somewhat in the dark because we don't know if it's the lack of sleep that kills or some other stress mechanism triggered by the lack of sleep.
Either way, the relationship between sleep and stress is known and experienced by many people every day.
A lack of sleep leads to increased stress levels, and increased stress levels disrupt sleep, which increases stress levels, which disrupts sleep.
The cycle is vicious and destructive on a cellular level, which is the worst level of destructiveness if you're alive and hoping to stay that way.
Currently, two-thirds of people in the UK suffer from disrupted sleep, with