We need more sleep but are getting less. A YouGov poll for Five News found that more than two thirds of Britons are failing to get the recommended eight hours a night, and a third manage only six hours or less. Many of us, it seems, lie awake worrying - about finances (more than half of adults), rising fuel bills (37 per cent) and a fear of crime (15 per cent).

Winston Churchill, Margaret Thatcher and Bill Clinton may have managed on just a few hours of sleep each night, plus a few catnaps, but most of us end up feeling tired and grumpy.

Professor Jim Horne, director of the sleep centre at Loughborough University and author of Sleepfaring: A journey through the science of sleep (OUP, £14.99), says that the average person needs to sleep for about seven hours a night - though a few people need more, and some manage on only four or five hours.

“If all you need is that amount, fine,” says Horne, “but cutting down to five hours or less is certainly not recommended, particularly for people whose lifestyles are already overburdened.” In fact, says Horne, the cumulative effects of too little sleep won't just leave people tetchy - it is potentially risky.

There is plenty of evidence that long-term sleep deprivation can be unhealthy. Horne says that it can affect decision-making and cognitive functioning, and contribute to obesity, metabolic syndrome and related problems.

Last year, a study at Princeton University indicated that missing a whole night's sleep affects the hippocampus - the part of the brain involved in memory forming - and prevents it from forming new cells. Other studies have suggested a link between obesity and lack of sleep, and this year US researchers found that losing three consecutive nights of deep sleep could harm the body's ability to control blood sugar levels, raising the risk of diabetes.

But some experts say that those who sleep less may not be affecting their health adversely in the long term. Indeed, diminished sleep patterns may even instil positive changes in health and attitude - if you handle them well. Here we profile four people who remain sprightly on only four to five hours of sleep a night:

HOWARD BENTHAM, 42, is the presenter of BBC Hereford and Worcester's breakfast radio show. He lives in the Cotswolds with his wife and three children aged 7, 14 and 18. He gets 4 hours' sleep a night.

I have been presenting breakfast shows for seven years. I was a primary school teacher before doing radio and never got out of the student thing of going to bed at midnight or 1am and getting up at the last possible minute before work.

That had to change virtually overnight. My daughter, Molly, now 7, was born the week I started my first breakfast job. Thankfully, she proved not to be a baby that woke up a lot and my wife, Gail, took care of that side of things.

Now my day runs like clockwork. I'm up at 3.15am. Often I anticipate the alarm and only occasionally am I shocked awake from a deep sleep by it ringing. I have a 30-minute drive to work and am in the studios researching the items to be featured on the programme by 4.30am. My show is on air 6-9am and I often have meetings after that.

I once played sport to a high level, but now find I have little time for exercise other than the odd round of golf and cricket in the summer. Despite the way I live my life, the astounding thing is that I no longer feel as if I'm getting tired.

I still teach three afternoons a week and on those days I have an energy dip between 4.30 and 5.30pm so I frequently have a power nap. Even then, I never shut my eyes for more than 20 minutes and have mastered the art of micro-sleeping where I am unconscious for just 2-3 minutes but wake up feeling completely refreshed.”

Professor Horne says: Successful people who enjoy life and are on top of their jobs tend to sleep less.However, the 4-hour sleep that Howard gets is just about the tolerable limit long term.

MARK PERRY, 39, runs a deli and coffee shop, Delizioso, in Cookham, Berkshire. He lives in Bourne End, Buckinghamshire, and has three children aged 14, 12 and 2. He gets between 4 and 4 3/4 hours' sleep a night.

I worked on the London Underground for eight years, four of those as a driver on a Tube train, and my shifts changed my sleeping patterns for good. Before I did that job I had pretty regular seven to eight-hour nights. Now I often sleep for just four hours and the most I get is five.

At weekends, when I have the chance to lie in a little longer, my body clock won't allow it. I'm still awake at 5am, no matter what time I go to bed. Whenever I sleep an extra hour or two, which is rare, I feel awful all day. It's like I have a hangover that I can't shake off. When I first opened the deli in 2005 I was working extremely long hours - we were open until 9pm - and that did start to affect me. My wife and I also had a baby the following year and he contributed to my tiredness with his night-time waking routine. I tried going to bed earlier, but even then I would wake up, staring at the ceiling, at 2 or 3am, which seemed pointless. Now I work fewer hours and the sleep I get seems to suit me.

The shop now closes at 4.30pm and after that I have to rush around getting the vegetables and other fresh stock for the next day as well as doing the banking and accounts. In the evenings I relax by playing my guitar - I'm in a band and often play with them until midnight before making my way home and crashing into bed. I am also sure yoga helps me to relax - I attend a class twice a week and always come out feeling as if any tensions have lifted.

If I get a tired patch during the day it is usually between 10 and 11am. I drink coffee to keep me going, although I don't get through anywhere near as much as when I was driving trains, which could be as much as 15 cups a day. I never take naps during the week, but will do occasionally at weekends. They are never longer than 5-10 minutes.

Even if I don't get round to it because I am rushing around with the kids, it doesn't make any difference. I set my alarm but am always awake before it is due to go off at 5am.

Professor Horne says: A driven man, Mark should cut back on the coffee he relies on for a perk as it is no substitute for sleep. And he should try to get at least one short nap every day - napping is as good as yoga for revitalising the body and mind, if not better.

KYLE CATHIE, 59, is managing director of the book publishing company Kyle Cathie. She has three grown-up children and lives in London. Kyle gets four hours' sleep a night.

I am sure I inherited my sleep patterns from my mother. I recall hearing her up at 2 to 3am when I was young and, although my three siblings and three children sleep regularly, I am similar to my mother. I go to bed at midnight and usually wake up at 4am, feeling fine and itching to get going with the day.

I drink lots of coffee, then do the washing or other household chores and check my e-mails. Just before 7am I'll have a bath, which is my relaxation, and then I head for work at 7.45am.

I eat extremely healthily and get exercise from walking. I have two of my children popping in regularly for meals and a chat. My life is busy. At 2pm every day I hit a tired patch. It just happens and, wham, my energy goes down.

I never sleep at work, but on Fridays and weekends when I'm not in the office I succumb to this tiredness and shut my eyes for 15 minutes. That is usually sufficient. My daughter sometimes sleeps until 1pm because she needs it. I don't. I have no problem nodding off. I don't need sleep aids. I sometimes read in the bathroom before going to sleep because it relaxes me a bit. But then I hit the pillow and I am off.”

Professor Horne says: Older people can generally get by with less sleep. Kyle is probably a naturally short sleeper but still needs a nap and I recommend that she does that regularly. But she shouldn't overdo the caffeine in the morning.

How to be a better sleeper

To become a more efficient sleeper and avoid sleep taking over your life, take note of the following:

1. “The test of insufficient sleep is whether you are sleepy in the day or if you remain alert through most of the day,” says Professor Horne.

2. If you do sleep less at night, catch up with regular catnaps, which are a life-saving habit, says Dr Sara Mednick, the Harvard University psychologist and sleep expert. A six-year Greek study published last year showed how a midday nap could help to prevent heart disease.

3. Professor Derk-Jan Dijk, director of the Sleep Research Centre at the University of Surrey, says that most people who need to catch up on sleep “naturally feel the urge to nap between 1pm and 3pm, which is ideal”. One reason this is a prime napping time, says Mednick, is because it's when the sun is at its highest and temperatures peak, making us feel intuitively sleepy.

4. For the chronically tired, two 25-minute naps at lunchtime and after work may be enough to help you catch up on sleep debt. The first 20 minutes of sleep is usually rich in slow-wave sleep and therefore deeply relaxing.

5. Few people need more than 7-8 hours' sleep a night and any more than that is just a luxury, not a physiological requirement, Horne says.