Does the way you sleep affect your health? Cherill Hicks rounds up the seven most common sleep problems and has a warning for those planning to sleep in this weekend.
Most of us are all too familiar with the effects of a poor night's sleep - irritability, low energy and "brain fog" the next day, to name but a few. But for those who suffer from insomnia, the longer-term effects are more worrying.
Studies have linked sleep problems to obesity, heart disease, high blood pressure, diabetes and depression, while recent research has found that sleeping too much, as well as too little, increases the risk of stroke.
The US study suggested that for those with high blood pressure, regularly sleeping more than eight hours a night or fewer than five respectively tripled and doubled stroke risk.
So what kind of sleeper are you? And should you be worrying about how your sleeping pattern is affecting your health?
The Under-Six-Hours Sleeper
Margaret Thatcher famously made do with four hours a night - and with so much to pack into life, you can do the same, right? Not so, says Dr Vikki Revell, from Surrey University's Sleep Research Centre. "It's true that sleep needs vary between individuals and are partly determined by genes as well as age and lifestyle," she says. "Some people function well on far less sleep than others. But there is good evidence that just a single night of less than six hours' sleep has an effect on immune cells, gene expression and metabolism."
About a third of those getting less sleep than they need struggle to fall asleep in the first place, says Dr Neil Stanley, an independent sleep expert based in Farnley, Hampshire. In humans, he explains, sleep is essential for enabling the brain to recover so we can function and learn during the day. Unsurprisingly, less than six hours' sleep makes us forgetful and moody and can leave us struggling to concentrate or focus. Most experts blame sleep problems on our 24/7 lifestyle - specifically exposure to blue light from mobile phones and other gadgets, which suppresses the secretion of the sleep hormone, melatonin.
"Light exposure disrupts the circadian rhythm - the internal body clock that regulates sleep by making our bodies respond to light and darkness," says Dr Revell. "People should switch off or reduce their blue light exposure two hours before going to bed, or get an orange filter, which cuts down on blue light."
Peace of mind at bedtime is crucial, adds Professor Jim Horne, former head of the sleep research centre at Loughborough University. "You need to leave your worries outside the bedroom door," he counsels. One way of doing this is through cognitive behavioural therapy - the latest treatment for poor sleep. One interactive online CBT programme called Sleepio has been found in clinical trials to achieve a 54 per cent reduction in the time taken to fall asleep.
The Spanish thrive on a four-hour siesta, so shouldn't power napping do the same for you? Most experts agree that regular naps can have cognitive benefits: one study from 2008 found napping was more effective than caffeine as a way of coping with the post-lunch "dip", while US research has found that even catnaps of six minutes can improve learning and memory.
But daytime naps should be kept to less than 20 minutes, warns Professor Horne. Any longer and the "full-blown sleep cycle" kicks in, resulting in "post-sleep inertia", a condition similar to jet lag that leads to grogginess and thick-headedness.
Daytime sleeping can sometimes be a sign of diabetes, depression or chronic pain, especially in older people. And if you're using napping to catch up on sleep lost at night, it might be best to address the original problem.
The Disturbed Sleeper
You drift off to sleep without any problem, only to find yourself wide awake in the early hours, brooding over work, relationships or financial troubles. It's a pattern that affects about a third of insomniacs and can be a vicious cycle: the more anxious you are about getting back to sleep, the less likely it is to happen.
"Waking in the early hours happens during the lighter part of each 90- to 120-minute sleep cycle, known as rapid eye movement (REM) sleep," explains Dr Revell. Some research suggests that in the pre-industrial past, people would often wake up to eat, check the house was safe, talk or have sex, before going back to bed for a second sleep. Which will be of little comfort to those who have to get up for work the next day.
"If you're still awake after 30 minutes, it's best to get up, rather than stay in bed," advises Dr Stanley. Disturbed sleepers are also advised to keep the lights dim and do something - a jigsaw, for example - to stop the mind racing.
Waking in the early hours can also be caused by conditions such as the menopause, depression, diabetes, pain and heartburn. So if you suffer regularly it is best to get checked by a doctor.
The Couch Sleeper
It's 9pm and you're out like a light in front of the TV - only to have trouble falling asleep later.
"People fall asleep on the sofa because that's where they feel safe and secure," says Dr Stanley. "The problems begin later because the body clock has been disrupted. The advice is simple: either stay awake or, if you're that sleepy, go to bed."
Professor Horne says falling asleep regularly in the early evening may be a sign of disturbed sleep the night before, unknown to the sufferer. Disturbed sleep can also be caused by medical conditions that need checking out, such as sleep apnoea (where the throat muscles relax, interrupting normal breathing) or periodic leg movements (waking with a sudden jerk), and also by the side-effects of medication.
The Binge Sleeper
Is it possible to "catch up" by binge-sleeping at the weekend? Some research suggests that sleeping until noon on Saturday can help you bounce back, especially if you're young. Another study, from 2013, found that "recovery" sleep at the weekend may help prevent diabetes.
Not everyone approves, though. Dr Stanley says: "You wouldn't eat junk food all week, then only eat lettuce at the weekend to undo the damage. Sleeping in at the weekend - and maybe staying out late at night - will confuse the body clock further, which is why people then feel so awful on Monday morning.
"The most effective change people can make for good sleep is to stick to one wake-up time - seven days a week, 365 days a year."
Ever woken up by your partner getting up to use the bathroom, or the water running as he or she takes a late shower? You're not alone: a 2005 survey of more than 1,500 adults found disruptive bedmates caused their partners to lose an average of 49 minutes' sleep a night.
Partner-induced insomnia is a relatively modern malaise, according to Dr Stanley, forced on most of us by lack of space and social convention. "Couples need to negotiate their sleep roles, rather than just get irritable with each other," he says. "They need to discuss how to resolve issues. For example, if he comes to bed later, his pyjamas and toothbrush can be kept downstairs, or he could use a torch rather than switch on a light."
"Ideally, I believe partners should sleep separately if they have the space."
The Vampire Sleeper
Oversleeping is very rare but (just like its opposite) has been linked to a host of medical problems, including diabetes, obesity, headaches, back pain, heart disease and depression. Extreme sleepiness during the day, coupled with sleeping for unusually long periods at night may be caused by a rare medical disorder called hypersomnia; other possible causes include alcohol, medication side-effects and depression.
As for all-night clubbers, developing a habit of sleeping right through the day is not recommended. Research on shift workers shows that reversing our natural rhythm is associated with a host of health problems, including increased risk of breast cancer for women.
"Evolution has programmed us to sleep at night," says Dr Stanley. "Going against that has massive negative consequences."
- Canvas, Telegraph