Often it's just the rumble of a heavy-breathing husband (or wife) that disturbs our sleep in the middle of the night.
But sometimes an underlying health complaint can be the reason, says Dr Neil Stanley, an independent sleep expert.
'Most of us wake many times at night for a few seconds without realising it - it's the body's way of checking our environment is safe to keep on sleeping,' he explains.
Underlying health complaints can be the reason your sleep is disturbed at night - that, or your heavy-breathing partner's rumbles
'However, if there is a disturbance - be it internal, because of our health, or external - that will wake us up properly and make it difficult to fall asleep again.'
Here, with the help of the experts, we explain what those wake-up calls could mean…
LEG CRAMPS
POSSIBLE CAUSES: Too much fat in diet; statins.
The underlying cause of muscle cramps in the calf, thigh or foot at night isn't known, but they may be triggered by taking certain medications, such as statins.
One U.S. study found a 20 per cent increased risk of muscle problems, including cramps, in those on the cholesterol-lowering drugs. One theory is that statins affect levels of enzymes in muscle cells, which are vital for muscle functioning. Why the cramps strike at night is unknown.
Cramping your style: Muscle cramps may be triggered by certain medications (like statins) or an overly fatty diet
They can also be a result of pregnancy or over-exercising, both of which reduce levels of minerals such as calcium or magnesium, needed to help muscles contract and expand.
Cramps can also be triggered by a circulation problem, where the peripheral arteries that supply the legs become damaged, says consultant vascular surgeon Eddie Chaloner, of Lewisham Hospital, London.
This can occur when they become furred with fatty deposits, usually due to a fatty diet, or when high blood sugar levels in diabetes damage the vessels.
'Lying down means the leg lies at the same level as the heart, making it more difficult for blood to get to the foot. This can cause cramps,' he explains. Restless leg syndrome - the overwhelming urge to move the legs at night - can also trigger leg cramps.
Though there is no obvious cause, it may be triggered by low levels of the chemical dopamine, which is needed to control muscle movement. Taking a warm bath before bed and drinking water can help reduce the risk of cramps, says physiotherapist Sammy Margo, as can stretching exercises.
BREATHLESS
POSSIBLE CAUSES: Nocturnal asthma; heart condition.
Waking up feeling out of breath can be caused by night-time asthma, known as nocturnal asthma. More than five million Britons suffer from asthma, some of whom will only realise they have it because it wakes them at night. It can also trigger coughing fits.
Just lying down can bring on the problem, since mucus is more likely to accumulate in the airways, creating pressure on the lungs.
There's no cure, but avoiding triggers such as feather duvets can help, and your doctor may also prescribe medication to open the airways and prevent attacks.
If you wake gasping for air a couple of hours after going to sleep, this could be a sign of problems with your heart - even heart failure - and you should see your GP if this happens regularly.
A weak heart triggers a build-up of fluid on the lungs, says Dr Charles Knight, clinical director of cardiovascular services at Barts Health NHS Trust, East London.
CONFUSED
POSSIBLE CAUSES: Sleep apnoea.
Confusional arousal, as doctors call it, tends to happen when something wakes us from deep sleep and we can't remember where we are.
'We now know that some parts of the brain responsible for our consciousness can remain in a sleeping state when we wake up,' explains sleep expert Russell Foster, a professor of neuroscience at Oxford University.
'So although we may be able to speak or get up, we are not fully awake, which is why we may feel confused.'
If this happens frequently, it may be the sign of an underlying sleep issue such as sleep apnoea, a chronic disorder in which you repeatedly stop breathing during the night, causing you to wake from deep sleep, and characterised by loud snoring.
Losing weight, giving up smoking, and drinking less may help.
Head case: Night-time headaches can be caused by teeth-grinding, or are sometimes a sign that you haven't drunk enough during the day
HEADACHE
POSSIBLE CAUSES: Alarm-clock headache; teeth-grinding.
A common cause of night-time headaches is 'alarm-clock' headaches, so-called because they tend to strike at the same time every night - usually between 1-3am - which tend to affect the over-50s.
Although doctors are not sure of the cause, some research suggests that, ironically, drinking caffeine in the evening may help.
If the pain is severe, your doctor may prescribe painkillers.
Even more painful are cluster headaches, which can wake you at the same time for weeks on end, says Dr Andy Dowson, director of the headache service at King's College Hospital, London: 'It mostly affects men, and causes throbbing pain, usually behind one eye.'
Over-the-counter painkillers aren't strong enough, he adds - but your doctor can prescribe more effective drugs, such as verapamil.
Night-time headaches can also be a sign you haven't drunk enough during the day. The tissues surrounding your brain are largely made up of water. When they dehydrate, they shrink, and the pressure on your brain can cause pain.
Waking up with a dull ache in the jaw can be the result of teeth-grinding, adds Dr Ferber. Other symptoms include earache and headaches.
Studies show that people who snore or have a sleep disorder, such as obstructive sleep apnoea, are more likely to grind their teeth while asleep, as are those who smoke or drink.
A mouthguard may help and is available from your dentist.
BACK PAIN
POSSIBLE CAUSES: Mattress; infection.
Waking up with back pain is usually down to sleeping on a mattress that's too hard or soft. 'You need to change your mattress every eight to ten years,' says physiotherapist Sammy Margo.
'To find the right one, lie on your back and see if you are able to put your hand in the gap between your spine and the mattress. If there is a big gap, the mattress is too hard. If you can't get your fingers out easily, it's too soft.'
Back pain: A common cause of this is a mattress that is too hard or soft; alternatively, it may signal you have an inflammation of the discs in the spine
Sleeping with too many pillows can cause the neck and upper back to flex upwards, putting strain on the lower back. 'The best position is on your back with one pillow under your neck and one under your knees, as this will support the lower back,' she says.
If you already have arthritis, you may find yourself waking up with it at night. This is because inflammatory chemicals in the body are more active between 11pm and 3am, though it is not known why. Taking an anti-inflammatory before going to bed may help.
But if the pain is intense, and regularly wakes you, this may a sign of inflammation of the discs in the spine, possibly due to a bacterial infection, or - in rare cases - because of a tumour on the spine, says Lee Breakwell, consultant orthopaedic surgeon at Northern General Hospital, Sheffield. See a doctor to investigate the cause.
Waking up with stiff muscles is one of the predominant symptoms of ankylosing spondylitis, a form of arthritis in which the spinal joints become inflamed, leading to pain and stiffness in the neck and back, says Professor Alan Silman, medical director of Arthritis Research UK.
The problem is acute at night, as fluid in the joints thickens as we lie down, making it harder to move.
The condition usually develops between the ages of 15 and 35, and is three times more common in men.
The condition usually develops between the ages of 15 and 35, and is three times more common in men.
COUGHING
POSSIBLE CAUSES: Acid reflux
'The main cause of waking up coughing is stomach acid splashing up the gullet and irritating the back of the throat,' explains Mr Vishal Saxena, consultant gastroenterologist at the Queen Elizabeth Hospital, London.
Known as nocturnal or atypical reflux, it happens when the valve closing off the gullet from the stomach doesn't work properly, allowing stomach acid to escape. Lying flat allows the acid to move up through the chest before hitting the throat.
The condition particularly affects those who carry excess fat around their stomach,' says Charles Murray, a consultant gastroenterologist at the Royal Free Hospital, London, 'as this creates pressure on the abdomen, pushing the contents of the gut up the gullet.'
Coughing: A common cause of waking up hacking is nocturnal reflux - not eating before bed can help this
Mr Saxena advises not eating just before bedtime. 'It takes up to six hours for the stomach to digest a fatty meal - though only two if you eat something lighter, such as lean meat and salad.'
Raising the head of your bed or sleeping propped up on pillows may reduce the chances of an attack, as will taking over-the-counter antacids, such as Gaviscon, just before you fall sleep.
NIGHTMARES
POSSIBLE CAUSES: Medication.
Although stress is a leading cause of nightmares, they can be triggered by some medication, such as antidepressants and beta-blockers, which may affect our natural sleep cycle.
After a nightmare, many people wake with their heart racing. Our heart rate naturally rises during our dreaming stages of sleep, known as REM, explains Professor Foster. 'This makes it more likely for us to experience palpitations after a nightmare.'
ROOM SPINNING
POSSIBLE CAUSES: Infection.
If you wake up feeling dizzy, it's possible you're suffering from benign positional vertigo, says Ayham Al-Ayoubi, a consultant ear, nose and throat surgeon at Chase Farm Hospital, London.
It mainly affects women over 50, and is caused by microscopic fragments of calcium breaking off from the lining of the inner ear - usually as a result of infection or inflammation - and getting into one of the fluid-filled canals of the middle ear.
This confuses the balance system in the ear, and it sends jumbled signals to the brain, which brings on dizziness and causes the brain to wake us up.
Sleeping on your back with two pillows may help, as it stabilises the position of the head, says Mr Al-Ayoubi. If you wake up dizzy, firstly put on a soft light next to your bed. Don't close your eyes, as the visual messages from sight help re-order the confusing messages being sent to the brain. Then focus on an object for a few minutes.
Certain exercises, taught by a physiotherapist, can help, too.
SWEATING
POSSIBLE CAUSES: Alcohol; hormones.
A nightcap might help us drift off, but it can also trigger sweats, as alcohol causes blood vessels in our skin to widen, making us feel warmer.
Night-time sweating can also be a side-effect of antidepressants, which can increase levels of stress hormones such as noradrenaline, says Dr Declan Leahy, consultant psychiatrist at the Private Psychiatry clinic in Kent.
It can also be caused by low levels of hormones. In women, levels of oestrogen, important for maintaining body temperature, drop just before or during a period, or during the menopause.
Men who sweat at night, even when it isn't particularly warm, could have a low testosterone level, says Christopher Eden, consultant urologist at the Royal Surrey County Hospital, Guildford.
Testosterone is also crucial for controlling body temperature.
In rare cases, night sweats can be a sign of underlying illness such as heart problems or cancer. If they occur a few times a week, see a GP.
Burning thirst: Night-time dehydration can be a sign of diabetes, or simply the result of sleeping with your mouth open
THIRSTY
POSSIBLE CAUSES: Hormones; sleep position.
Night-time thirst may be a sign of diabetes insipidis, a condition unrelated to diabetes type 1 and 2. The body becomes unable to regulate water levels, due to a shortage of the antidiuretic hormone. Symptoms seem to worsen at night.
However waking up thirsty can also be a sign of undiagnosed diabetes type 1 or 2, as high levels of sugar in the blood trigger thirst. Other symptoms include losing weight, blurred vision and excess trips to the loo, especially at night.
Waking up feeling thirsty can also simply be the result of sleeping with your mouth open.
WAKING SEVERAL TIMES
POSSIBLE CAUSES: Age; medication.
The older we get, the lighter our sleep becomes, so we are more easily disturbed by external factors such as noise. Neil Stanley recommends your bedroom should be cool (around 16c) and dark.
Some medications can disrupt sleep, including those for high blood pressure, and cold and flu remedies, which often contain caffeine.
NEEDING THE LOO
POSSIBLE CAUSES: Enlarged prostate; age; unstable bladder.
Waking to go to the toilet at night is common in men over 50, because the prostate gland enlarges naturally with age, pressing on the bladder, says Robert Calvert, a consultant urologist at the Royal Liverpool University Hospital.
It can be treated with medication to relax the muscles in the prostate and shrink the gland. And always see your GP, as it can also be a symptom of prostate cancer.
Chris Eden, consultant urologist at the Royal Surrey County Hospital, says our kidneys make more urine as we age, due to decreased levels of the antidiuretic hormone.
Bladder instability, which affects men and women of all ages, is another reason we wake, says Mr Eden. 'It causes the bladder to contract when only partly full, signalling it needs to be emptied. This is more noticeable at night, as it disrupts our sleep.'
It can be treated with medication, but the underlying causes can include kidney stones and cancer, so see your GP.
Read more: http://www.dailymail.co.uk/health/article-2381003/So-THATS-waking-From-heart-failure-diabetes-fatty-diets--bodys-trying-tell-night.html#ixzz2aXiUUl1z
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