1. You're dehydrated
Even mild dehydration can severely hamper your energy levels: researchers at the University of Connecticut found that both men and women struggle to perform simple tasks when they haven't taken in enough fluids.
Another recent study, from Loughborough University, found that dehydrated drivers make the same number of mistakes as drunk drivers. So next time you're feeling tired, drink a glass of water and see what a big difference it can make.
Find out more about dehydration symptoms and learn some strategies for staying hydrated
2. You're a smoker
Smokers tend to suffer poorer sleep quality than non-smokers, according to a German study. The reason? Researchers believe it may be due to the stimulating effects of nicotine. 'If you smoke and suffer from sleep problems, it's another good reason to quit,' says lead researcher Stefan Cohrs.
Get started with our guide to giving up smoking
3. You could suffer from sleep apnoea
If you constantly feel tired despite a full night's sleep, there could be an underlying medical reason. An example? Sleep apnoea – a condition where your throat narrows or closes during sleep, repeatedly interrupting your breathing. This causes you to wake frequently throughout the night – sometimes without realising it – and feel exhausted the next day. Smoking and alcohol can make the condition worse. Worried? Speak to your GP.
Dealing with sleep apnoea
4. Your pet's to blame
Nearly 60% of pet-owners allow their cats or dogs to sleep in the bedroom, according to a study at the Mayo Clinic Sleep Disorders Center in the US. And more than half of these animal-lovers admit their sleep is disrupted to some extent by their four-legged friends. Don't want to lock Rover or Tiddles out of the bedroom? It may still be wise to employ some damage limitation: you could invest in a timed pet-feeder to avoid being woken up when the cat fancies an early breakfast, for instance.
5. You need a new bed
A bed's quality may deteriorate by as much as 70% from its new state after 10 years, according to a study by the Furniture Industry Research Association. Even after just six years, your mattress could offer significantly less support than a new one, due to wear and tear from body weight, movement, sweat, skin, hair and other debris. So you spend much of the night trying to get comfortable, which means your sleep quality is impaired.
6. You're not getting enough fresh air
Spend most of the day indoors – particularly during winter – and your brain will respond to the lack of natural light by producing more of the sleep hormone, melatonin. So you'll constantly feel ready for bed, even after a good night's slumber. The solution? Make sure you spend time outdoors every day, even if it's just pottering in the garden.
Ten reasons to get outdoors more
7. You're not moving enough
Sitting in the same position for long periods of time can make you feel sleepy. Even if your brain is engaged in looking at the computer or TV, you need to remind the rest of your body you're awake. Do remember to get up, stretch and move around as often as you can.
How two minutes' activity an hour can help your health
8. You're not getting enough iron
One of the most common medical reasons for feeling tired all the time is iron-deficiency anaemia. This is when lack of iron leads to a reduction in the number of red blood cells, which hampers vital oxygen flow around the body. One solution, of course, is to up your iron intake: dark green leafy vegetables, fortified cereals, beans, nuts and seeds are all good sources. Alternatively, a supplement may help: taking iron tablets can reduce tiredness in women by up to 50 per cent, according to a recent study published in the Canadian Medical Association Journal.
Find out more about the health benefits of iron
9. You overdid the booze
Even just one or two alcoholic drinks close to bedtime can interfere with your sleep quality. On a normal night, you'd usually have six or seven cycles of deep slumber alternating with lighter, rapid eye movement (REM) sleep. But if you've been drinking, you'll typically only have one or two, so may wake up exhausted.
Find out more about how alcohol affects the body as we age
10. You need to paint the bedroom
The secret to a sound night's slumber? Sleep in a blue room. That's the finding of a 2013 study, commissioned by Travelodge. Chris Idzikowski, sleep expert from the Edinburgh Sleep Centre, explains: 'There are specialised receptors called ganglion cells in the retina part of our eyes, which are most sensitive to the colour blue. These receptors feed information into an area deep in the brain that controls 24-hour rhythms, and affects how we perform and feel during the day. That interaction between light, sleep and wakefulness is supremely important.'