Speaking about Sleeping, session three. Beliefs about sleep. How much sleep do we need?

And this is where things start to get interesting. How much sleep do you think you need? Seven and a half hours? Eight hours? We've been brought up and we read so much in social media about poor sleep and how bad it is, and then we're given a number that we're supposed to sleep for. And these do nothing for helping us to sleep because when we wake at night or we're not getting to sleep and we've put things off and we're worrying about all sorts - we'll worry about not getting enough sleep and that doesn't make us sleep more it makes us sleep less.

So the simple answer is six to ten hours. That is a huge range. And remember that there are outliers to that. There are going to be some people who need less, and some people that need more. My friend Dorothy, she happily slept for nine and a half hours, it meant she was hopeless at a party.

You may know, depending on your age and your terms of reference, that Thatcher, Margaret Thatcher, another type of party was famous for catnapping and not needing to sleep much in the night, so she had lots of time to write rather ghastly policies. Churchill apparently didn't sleep for long hours either and Einstein did. Take from that what you will.

Anyway, suffice to say, the average amount of sleep is six to ten hours and we might be an outlier. We might need less than that. Sleep also changes across the life spectrum. Babies and teenagers need the most sleep. And people after roughly, and remember everything is an approximation, people over the age of 80 sleep across the day more. They break their sleep up and might spend more of the night awake and more of the day asleep.

There are larks and owls. So some of us are really good in the mornings and some of us are much better at night. There seems to be an evolutionary reason for this. So if you're in a primitive tribe, you want 24 hour cover. You want there to be cover early in the morning and later at night. So it makes sense if you've got roughly 50/50 of your peoples being better in the morning and better at night. You've got good cover. Here in my life, I'm the early morning person when we're lambing. I do the early morning checks. My husband very good at tinkering away under a tractor at about 11 o'clock at night.

So there is that spectrum and as well there'll be people who just good in the day. They wake in early morning and they go to bed at normal night time and that's how they are so there's there are definitely patterns of preference and genetic I would say propensities to sleep and be awake at different times of the day. Nothing wrong with that.

Half the problem can be trying to fit yourself in to something that you think you should be. Another misperception is about the amount of deep sleep that we need. So actually, the amount of deep sleep we need is really only around one and a half to two hours. Sometimes less than that. There'll be outliers to that too.

Deep sleep comes at the first part of the night. There is another misperception, a sort of old wives tale. Am I allowed to say that? I'm not sure. That one hour spent asleep before midnight is worth two after midnight. We can see where that comes from. There is a deep sleep that takes place earlier in the night.

But if you're a person that doesn’t need to go to bed until 12, that could be troubling. And it's not true. There are different parts to the sleep cycle, there is deep sleep, there is REM and that's where we dream and that comes quite often, you might notice if you're waking in the morning that you're more aware of your dreams, so that can come in that pre-waking up phase.

You can't die of no sleep unless you are very unlucky and have a condition called fatal familial insomnia. Luckily, in 2012, there are only 26 cases in the whole world, and if you don't know of a person in your family that's died of it, you are not going to die of it. It is also worth knowing that even with poor sleep, less sleep, broken sleep, there is an ability to function well.

And I take inspiration from people like Ellen McArthur and Pip Hare, amazing single-handed sailors who do a race called the Vendee Globe, and they're on their boats for several weeks at a time, highly technical, big boats,  in very dangerous seas. They have broken sleep, patches of sleep, 10 minutes here, 20 minutes there and they come back and they're tired but they are still able to handle a technical breakable boat in very dangerous seas.

So I think the message here is that there is a wide variation in the amount of sleep we need and if you're tired, you will find sleep. You will just fall asleep. Basic take home - don't worry too much. Next time, we're going to work out how much sleep do we need at this time.