The notion that eight hours sleep is essential to health is widely repeated, but -- as we've noted before -- fails to take into account that individual requirements vary. Something else you probably didn't know: the idea that we need a long continuous period of sleep is a relatively modern innovation.
Picture by Phil & Pam Gradwell
Stephanie Hegarty at the BBC World Service highlights a wealth of evidence which suggests that a "segmented sleeping pattern" -- where people would sleep for four hours or so, be awake for a couple of hours and then sleep again -- was very much the norm up until at least 1700. Note that this didn't necessarily mean being highly active during the interim "waking" period; it might simply mean reading, meditating or enjoying the attentions of someone else in the same bed.
Oddly enough, a major factor in the change was the emergence of lighting both in public places and in the home. When resting hours were entirely dictated by whether there was natural light, there was more time in total for "relaxing" without necessarily sleeping. Once it was possible to be active at night, it also become more practical to concentrate sleep in one burst.
The practical upshot? Stressing because you wake up in the middle of the night before dropping off again isn't sensible. For more advice on sleeping, check out our top 10 tips for better sleep.
The myth of the eight-hour sleep [BBC News]