Lie-ins are good for you Sleeping couple
False: A short lie-in won't do you any harm, but longer ones aren't particularly beneficial and might make you feel groggy.
"What the body really wants is regularity, and anything that moves you away from that starts causing the body a problem," says Dr Neil Stanley from the Surrey Sleep Research Centre.
"The body enjoys getting more sleep so restarts its natural cycle - and you may wake up in an inappropriate stage of sleep, which throws us."
The more you sleep the healthier you are
True: According to the US National Sleep Foundation's 2003 Sleep in America survey of older Americans, the better the health of older adults, the more likely they are to sleep well.
The reverse is also held to be true. Sleep Researcher Dr William Dement stated that sleep-deprived people are less happy and more stressed than those getting eight hours a night.
"I consider sleep deprivation a national emergency," he says.
The older we get, the less sleep we need
False: Or rather, it's hard to tell, says Dr Stanley. "We know that young people sleep more than older people, but how an individual changes over age isn't well known.
"Many times when you talk to the elderly they'll say they only sleep for six hours a night but are actually having two hours in day, so it's hard to tell. There's no definitive science to back up the claim."
It's dangerous to wake a sleepwalker
False. It isn't dangerous in the sense that it won't seriously harm the sleepwalker, but sleep experts say that it could alarm or confuse them. It's probably best to try to get the sleepwalker back to bed.
Some people need very little sleep
True. Bill Clinton snatched just five to six a night and Napoleon didn't need much. Perhaps most famous of all short-sleepers is Margaret Thatcher, who was happy leading the Conservative Party on just four hours a night - "provided that about one day a week you have a night when you can have longer," as she told Brian Lamb in a BBC interview.
Says Dr Stanley, "These people are at the extreme end of the spectrum, but if you need three hours' sleep then that's what you need, and if you need 11 hours the same applies! We do know that it's easier for an 11-hour-a-night person to lose an hour than it is for a three-hour person.
The question is: were these people really short sleepers, or did they just not allow themselves more sleep?"
Power naps are good for you
True: Naps give rise to all sorts of biological benefits, such as cell repair, hormonal maintenance and better heart function. Dr. Sara Mednick, a sleep researcher from the Salk Institute for Biological Studies, says that slipping rapidly in and out of rest maximises such benefits.
And Power Sleep author Dr. James Maas writes that a 20-minute afternoon nap gives more rest than sleeping for 20 more minutes in the morning.
Shame, then, that the Spanish government has just abolished siestas in favour of shorter working days. The research that backed the decision found that almost 50 per cent of Spaniards work overtime, but that the siesta "is responsible for an underpaid and exhausted workforce".
Sleep alone and you sleep better
True: At least, that is, if you're one of the 23 per cent of partnered adults who featured in a 2005 NSF survey, and frequently slept solo because of their loved one's bad nocturnal habits.
According to the survey of 1,506 adults, disruptive bedmates caused their partners to lose an average of 49 minutes' sleep a night.
You can 'catch up' on sleep
True: But it may not be that good for you. According to Mary Carskardon, Director of Vhronobiology and Sleep Research at EP Bradley Hospital in Providence, Rhode Island, teenagers catch up on lost shut-eye by 'binge sleeping', which does help replenish stores of sleep.
But it has a negative impact, because it's giving the brain a different message about when night time is - not so useful for Monday morning when it's time to get back to work.
Sleeping on your side helps you stop snoring
True: Snoring is worse when you lie on your back, because your tongue relaxes and blocks your airway, so lying on your side can help.
Snoring is also associated with being overweight so losing a few pounds could be helpful - as could giving up smoking.
We're all either morning or evening types
True: Research from the University of Surrey's School of Biomedical and Molecular Sciences showed distinct differences in the circadian rhythms (our natural genetic clock) of those who took part, with "larks" going to bed early, getting up earlier and being more alert, and "owls" staying up late, waking up later and feeling more alert at night.
The study showed that a person's genes may predispose them to being an early bird or a night owl.
Successful sleep tips
The National Sleep Foundation (NSF) advises:
- Use your bedroom only for sleep and sex.
- Avoid big meals close to bedtime - spicy, heavy or fatty foods can cause heartburn and discomfort at night.
- Take regular exercise - but not late at night. Exercising produces stimulants that stop the brain from relaxing quickly, and being too hot is also associated with lack of sleep.
- Avoid having caffeine at least six hours before going to bed.
- Set specific times for going to bed and waking up. Night-time habits will help set your body clock, getting it ready for sleep and making it aware of sleep times.
- Make sure your bed is comfy. Change the mattress every nine to 10 years and get the right shape pillows for your head (a good bed shop can help you work out what's best).
- Create a calm environment in your bedroom - use blackout blinds and check your room for noisy distractions.