Last week a sleep colleague and I gave a presentation to a group of GPs. It was one of those slightly disorganised things where you know what you’re presenting but not a great deal about anyone else’s presentation. Our introduction by a GP colleague of ours gave a light-hearted overview of the importance of sleep… including a recent discovery that our belief that we need 8 hours sleep was a myth. I felt slightly panicked at this suggestion. In most part because I couldn’t believe I had missed a news story this big. Had I really not been paying attention to my RSS feeds that week? However, after a quick search, this is what I found:
BBC News Magazine: The myth of the eight-hour sleep **
Reading this title, what’s your first thought? That we don’t need 8-hours sleep, right? Hands up anyone who thought ‘I knew that I could get away with 6’?
But in fact, this is not what the BBC article reports. It discusses the concept of biphasic sleep — sleeping in two, approximately 4-hour chunks across the night. This concept is not a new one. As the article points out, there are many historical reports of individuals waking for a couple of hours in the middle of the night. In general, these hours were whiled away with activities such as reading, writing, chatting or intimate relations. Note, there were no electrical light, TVs or tablets in these historical times. Bed time was a lot earlier than ours, and the time available for sleep from bed time to final wake time was a lot longer.
I am not particularly knowledgeable of the historical accounts of this phenomenon but it has been studied scientifically. In the early 1990s, Thomas Wehr investigated the effect of changing the length of daytime light exposure (and conversely, night length) on sleep, and found that with long nights, human sleep occurs in bouts, with periods of quiet wakefulness during the night. Wehr hypothesised that it was our modern sleep/wake pattern, with considerably and chronically shortened sleep periods, that increased sleep propensity and drove consolidated sleep. When Wehr gave people a 14-hour sleep opportunity, they had a few days of catch-up sleep (11-hours in total!) followed by sleep in two main bouts, with a period of quiet wakefulness in between. Each bout lasted about 2-5 hours with the wakefulness period lasting 1-3 hours. How long did these people sleep in total? 8.25 hours on average.
** If you didn’t think that one was misleading, have a look at this. I suppose, an exercise in what happens if you rip off another’s news article without reading any of the background material.