Online Class Notes (Mike)

It is quite apparent that there are significant differences in sleep patterns in different parts of the world, and that sleep patterns have also changed over time. Traditions, cultural values and local conditions and environments all have a bearing on sleep practices and attitudes.

One major source of these differences is the widespread availability of artificial light, which, since its introduction in the mid-nineteenth century, has led to dramatic changes in sleep patterns in the industrialised world. It is thought that today we sleep at least an hour less each night than was the custom just a century ago, and probably several hours less than before industrialisation and electricity. According to some studies, artificial lighting has encouraged people to go to bed later and to sleep in a single concentrated burst throughout the night (monophasic sleep), rather

than the more segmented and broken-up sleep patterns (polyphasic or biphasic sleep) that were previously the norm.