Random Facts: Sleep

The feast day of the Seven Sleepers of Ephesus, a group of youths said to have hidden in a cave to escape religious persecution around 250 AD, fallen asleep and woken up 300 years later, is 27 July.

The legend has led to 27 July being celebrated as National Sleepy Head Day in Finland.

Giraffes only sleep for two hours a day.

Koalas are the sleepiest mammals: they sleep for between 20 and 22 hours a day.

A recent survey found that 12 percent of people dream in black and white. Before colour TV arrived, only 15 percent of us dreamt in colour.

Many aquatic animals, including ducks, whales and dolphins, sleep with one eye open. Half the brain sleeps while the other half is alert.

In 2008 it was found that sloths in the wild sleep no more than human teenagers. Sloths in captivity, however, sleep about 16 hours a day.

Difficulty getting up in the morning is known as dysania or clinomania.