This article from the BBC describes a sleeping pattern involving two sleeps of about 4 hours with a period of wakefulness in between, known as segmented sleep. It seems there is evidence that this was the normal sleep pattern until the night was pushed back by street lighting at the end of the 16th century.
During this waking period people were quite active. They often got up, went to the toilet or smoked tobacco and some even visited neighbours. Most people stayed in bed, read, wrote and often prayed. Countless prayer manuals from the late 15th Century offered special prayers for the hours in between sleeps.
This is interesting to me as I have experienced long periods of wakefulness at night for most of my life. Recently I underwent a sleep test and was diagnosed with mild sleep apnea. The recommended treatment was a dental device manufactured by Sonomed an Australian company. After an adjustment to reduce the pressure on one of my teeth the device is now relatively comfortable to wear – it takes some getting used to having two substantial pieces of plastic in your mouth all night!. The device works by preventing the lower jaw from dropping back during the night which causes the throat to close and the airway to be occluded. The brain reacts by waking you up to some degree. This may occur many times every hour and is can be quite disturbing to anyone sharing the bed with you!
So far I am positive about the Sonodent and look forward to having more energy during the day.