Thursday, February 01, 2007

What is enough sleep?

A question posted in LinkedIn: "Sleep less, live longer? What is enough sleep?"

The responses are quite interesting. Most people would say 6, 7, or 8 hours is "right". Some even say that if they don't have at least 8 hours of sleep everyday, they can't function the next day.

One even go as far as: "I figure I'll get enough sleep when I'm dead. There's too many fascinating things to do in life -- including work... "

The Royal College of Psychiatrists has a leaflet on sleeping well. How much sleep do we need?

This depends mainly on how old we are.
  • Babies sleep for about 17 hours each day.
  • Older children only need 9 or 10 hours a night.
  • Most adults need around 7-8 hours sleep each night.
  • Older people need the same amount of sleep, but will often only have one period of deep sleep during the night, usually in the first 3 or 4 hours, after which they wake more easily. We also tend to dream less as we get older.
There are also differences between people of the same age. Most of us need 7-8 hours a night, but some (a few) people can get by with only 3 hours a night. It's not helpful to regularly sleep more than 7-8 hours each night.

The short periods of being awake feel much longer than they really are. So it's easy to feel that we are not sleeping as much as we actually are.
Of course, there are other studies and surveys. Each has its own conclusion, which makes it more interesting.

An article in says:
"There is really no evidence that the average 8-hour sleeper functions better than the average 6- or 7-hour sleeper," Kripke says, on the basis of his ongoing psychiatric practice with patients along with research, including the large study of a million adults (called the Cancer Prevention Study II).

And he suspects that people who sleep less than average make more money and are more successful.

The Cancer Prevention Study II even showed that people with serious insomnia or who only get 3.5 hours of sleep per night, live longer than people who get more than 7.5 hours.
Another one from an interview in CNN:
The sweet spot appeared to be somewhere between 6.5 and 7.5 hours a night. Those are the people who lived the longest. Now if you got less than 4.5 to 6.5, you were probably going to live longer than those who slept more than the sweet spot.

Hmm... I would conclude that for most people "around" 7 hours of sleep is the best, i.e. healthy yet productive. Also, sleeping less seems to be better than sleeping more...