20 June

Another interesting tidbit for those who sometimes struggle with sleep. By the time a person is 50, it's quite common for them to fall asleep about 9pm and be awake by 3 or 4 am. This trend starts in many in their 40s, and is thought to reflect an evolutionary history of older people keeping vigil at night in dangerous situations. Our sleep didn't evolve in quiet rooms inside warm and comfy beds, so the '8-hour sleep' is probably more an artefact of modern electric lighting and lifestyles. 'Bad' sleepers are much more the norm, in historical terms. Another example of how I think people always need to look at the assumptions behind research, well before they look at the research itself.