Stress activates the fight-or-flight response and it makes sense evolution wise that when we feel threatened or in danger, we should stay awake. And it can be a vicious circle -- stress can stop you sleeping, but not getting enough sleep can also create stress.
Our bodies metabolise the stress hormone cortisol during sleep, but a shortened sleep can mean that cortisol levels do not decrease enough and so you wake up feeling stressed in the morning.
Over time, this can impact on your immune system and hormonal health.
We have so many distractions and reasons to stay awake these days, from the internet and 24-hour TV to social media sites and computer games, that many of us are simply over-stimulating ourselves in the evenings.
Exposure to bright lights at night, from TV or computer monitors, can affect melatonin levels and thus disrupt the sleep cycle. But it's not just what we do in the evenings, what we do during the day can also have a stimulating effect that lasts well into the evening.
As a nation we're drinking more coffee than ever before, which may keep us buzzing during the day but could be having a significant affect on our sleep. The stimulating action of caffeine affects the central nervous system, which increases heart rate and adrenaline and also suppresses melatonin production.
It takes up to eight hours for the body to break down caffeine, so drinking coffee during the day, can easily disrupt sleep at night.
It's true that while some foods can help you sleep (see below), others can have the opposite effect. Spicy, sugary, high-protein or high-fat foods eaten late can lead to sleep-busting heartburn or indigestion. Ideally, you should eat dinner two to three hours before bed to allow your body time to digest.
Alcohol is a sedative and can help you nod off initially. One drink may be okay, but if you have two or more it can prevent you from getting into the deeper stages of sleep which are essential for feeling refreshed.
Sleep-inducing foods contain the amino acid tryptophan that has a calming effect on the brain, which makes it easier to fall asleep and stay asleep.
Your body converts tryptophan into the hormones serotonin and melatonin, both of which have a relaxing and sleep-inducing effect.
Tryptophan is found in many high-protein foods, but to get the benefit of tryptophan's sleep-inducing qualities you need to choose a snack that combines both protein and carbohydrate, see below.
Sleepy Time Snacks
>Porridge made with milk
>Handful of almonds with a banana
>Oat cake with peanut butter
>Natural yogurt with granola
>Cottage cheese with a slice of apple
Good Sleep Rules
>Avoid weekend lie-ins -- your body can't store sleep, so it won't make up for any lost during the week. In fact, it will just disrupt your sleep pattern further.
>Sleep Sex Rule -- do not use your bed for anything except sleep and sex, don't read, eat or watch television in bed.
>Avoid afternoon naps -- a very short cat nap of less than 10 minutes may be helpful but anymore than that can affect your sleep at night.
>Keep the light out -- even a small amount of light can hinder sleep so try black-out curtains or blinds or perhaps an eye mask.
>Have a warm bath before bed -- studies show a drop in body temperature triggers the brain's sleep response. A bath artificially raises it, so when you cool down again you feel sleepy.
>Avoid stimulating activities before bed -- give yourself at least one hour to wind down before bed. Avoid using your computer, smartphone or other gadgets during this time and refrain from watching or reading anything that will get you riled up.