Feeling tired throughout the day could suggest a problem
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A survey is suggesting that only a tiny minority of us are getting eight hours' sleep a night. But do we really need that much?
"Getting your eight hours" is one of those injunctions, like drinking plenty of water or not to swim in canals, that most people take at face value.
When former Prime Minister Margaret Thatcher was reported to need only five hours' sleep a night, it was taken as evidence of a near-supernaturally tough constitution.
And it's become an increasingly common sentiment that too much work and stress and missing out on our eight hours is the modern plague.
We don't need any set of amount of sleep - it's all down to genes and whether we feel fresh and alert during the day
But the good news, says Prof Jim Horne, director of Loughborough University's Sleep Research Centre, is that we don't need eight hours at all.
"It's nonsense. It's like saying everybody should have size eight shoes, or be five foot eight inches.
"There is a normal distribution - the average sleep length is seven, seven and a quarter hours."
Lots of people report having more or less than the average, he said. It may all be down to genes, and what people are accustomed to.
The US National Sleep Foundation suggests seven to nine hours a night is advisable for adults, and a survey it conducted in 2002 suggested three-quarters of Americans had problems sleeping and a third were so sleepy during the day their activities were affected.
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The foundation says: "In the past century, we have reduced our average time in sleep. Though our society has changed, our brains and bodies have not. Sleep deprivation is affecting us all and we are paying the price."
But Prof Horne says: "The test of insufficient sleep is whether you are sleepy in the day or if you remain alert through most of the day."
In a nutshell, if you sleep for eight hours a night go to work and find yourself lolling and drooling on the keyboard, you aren't getting enough. If you're sleeping five hours and running the country, you probably are getting enough.
And Prof Horne, the author of Sleepfaring: A journey through the science of sleep, says the idea that Victorians got lots of sleep and had a better work-life balance is a myth.
Indeed a classic demand of the 19th Century labour movement was "Eight hours labour, Eight hours recreation, Eight hours rest".
Women may need more sleep than men, Prof Horne says, due to the structure of their brains. And he says there is evidence that young children are getting too little sleep, with a detrimental effect on their behaviour.
Sleep patterns disrupted by shift work have been linked to heart disease, but this has also been linked to stress caused by unpleasant jobs, Prof Horne notes.
He stresses that sleep disorders are a 24-hour phenomenon with sufferers spending their days stressed and unable to clear their heads at night.
Leaving the bedroom and doing a jigsaw is one course of action, Prof Horne says. And the insomniac must not dwell on his problems or his condition.
As Mrs Thatcher once told the Sun: "If you brood and brood and brood... you won't go to sleep."
Below is a selection of your comments.
I was told at uni that sleep is cyclical and that as long as you wake up during the lighter part of the sleep cycle you will feel fresh and alert. Wake up during the heavy sleep part and you will be a like a bear with a sore head all day. I think there are even devices on the market now that detect these cycles and wake you at the right moment.
John D, Glasgow, UK
Very interesting - but more to the point is not the length of sleep but when it takes place. My internal clock seems permanently to be set to British Summer Time and I automatically feel energized when we put the clocks forward (which means I go to bed effectively an hour earlier). I don't sleep for any longer but it is considerably more refreshing. Somehow I never seem to be able to overcome the 'jetlag' of GMT!
Garry Humphreys, London
Why does it have to be continuous? I have a 10-20 minute period in the afternoon where, if I'm honest, I would be better off crashing before carrying on. In other countries that would be the siesta period...
I can cat nap, my girlfriend can't.
Allan, St Albans, UK
As a child growing up in London, we were told an old adage that the requrirements for sleep were:- By Nature 5, by Custom 7, by Laziness 9 and by Wickedness 11.
Needless to say we were not allowed long lay-ins in the morning!!
Anne Merryweather, Limerick, Ireland
Alcohol and coffee (any caffeine, really) have a detremental effect on our ability to sleep properly. Go without for a week and see the effects! Easier to get to sleep, deeper sleep, better stamina & concentration throughout the day, less tired driving... The only problem is I really like wine & coffee!
I can't physically sleep for 8 hours! If so, I'll be sluggish or in a bad mood all day.
Andrew McGreevy, Bournemouth
The most disruptive thing towards sleep patterns is the 9 o'clock start at work. Which lunatic ever decided that 'the day' should start at 9? It would be more sensible to work 12 till 8. That way people will naturally wake up and be more alert in work. It will also give families time to have breakfast together.
Daniel Meadowcroft, Stockport, England
....but strangely no mention in the article of the feelings associated with having too much sleep. If on the odd occasion i allow myself a very big lie in, the rest of the day is a right off, feeling like i've been asleep for years and really not able to wake up!
Ed S, London, UK
This is report is nonsense. How can it be natural for an alarm clock to forceable wake the body up? Why do some countries have a siesta? Humans need at least 8 hours sleep and I would even say 10 for myself!
I think the reason the Americans are so sleepy all the time is because they eat too much(carbohydrates) not due to the fact how much they sleep!
I agree with this entirely. I find that going to sleep at 1am, and waking up at 7am i feel fresh all day. Whereas if i sleep for "8 hours" i actually feel worse for it. I occasionally lie in on weekends and perhaps get 8 or 9 hours then, but thats a rarity.
Eight hours, I've never been able to sleep for that long.
I manage and continue with about 4 hours a night and have been doing so for a considerably long time now. It takes me a while to go off whatever the time of night and always I wake before any alarm that might be set, for work.
Every time I hear a debate regards too little sleep, Professor Horne of Loughborough University is wheeled out to say it is all rubbish that we need 8 hours sleep.
Then why is that most people I speak to these days say they feel shattered and just want to go to sleep,and when I ask these people how much sleep have they had they always say below 7 and half hours.
The evidence is staring us in the face - we're not getting enough sleep! Too much late night television might be a good start for any meaningful research into this problem!
Bill O'Rourke, Lancashire
I think we're a sleep-deprived nation. People don't seem to value their sleep - they seem to view it as time wasted. But sleep is vitally important to a happy, productive life.
Andrew Thomas, Swansea, UK
Sometimes I find that I nod off in the middle of a
John Airey, Peterborough, UK