Just how much sleep you need each day will depend very much on your age and your state of health. But sleep is not simply about the time that you spend sleeping, but is also very much a question of the quality of that sleep. So, if you are getting the right amount of sleep and are still getting up each morning feeling tired and going through your day unable to concentrate fully, and perhaps being a little irritable, then there's a very good chance that you're not getting enough deep sleep and could well be suffering from insomnia.

When it comes to age, newborn babies clearly need the greatest amount of sleep and will normally sleep in cycles of about four hours waking when it's time to be fed and changed. Typically, a newborn baby needs between fourteen and sixteen hours sleep each day.

By the time infants reach the age of about four to six months they should be sleeping through the night and will start to spend longer periods awake during the day when they will begin to take a greater interest in their surroundings and start to play. At this stage their need for sleep will drop slightly, but they will still need anywhere from about ten to fourteen hours sleep a day.

Surprisingly enough older children and even teenagers should also be getting a similar amount of sleep and ten hours sleep a day for children is a good figure to aim for.

For many years it has been thought that children, and particularly teenagers, who were sleeping for more than about eight hours a day were simply lazy, but this is in fact far from the case. Bearing in mind the level of activity that most children are involved in each day, both at school and in their free time, and the fact that their bodies are growing and changing rapidly, there is a genuine need for more than the traditional eight hours of sleep if they are to be given the best conditions for development.

For most adults eight to eight and a half hours sleep each night is just about right and this should be sufficient to allow the body to recharge it's batteries and have you up and about, alert and refreshed each morning.

Another myth is that as we get older we need more sleep. This again is not the case, unless there are also accompanying health problems, in which case more sleep may be necessary. A tendency for older adults to 'nap' during the day is often taken as a sign that they need more sleep but in reality the daytime nap is invariably offset by sleep less during the night.

One exception in the case of adults is that of pregnant women, who should generally increase their sleep during this time by about two or three hours.

The test of whether or not you're getting enough sleep is a fairly simple one and involves nothing more than assessing whether or not you feel refreshed when you get up in the morning and are able to function normally and focus on the tasks at hand during the day. If you find yourself unable to concentrate or dozing off during the day then you're probably not getting enough sleep.

Missing the odd few hours of sleep here and there will not do you any harm but if you find that you're regularly falling short on sleep then this can have serious consequences. We all suffer from the occasional insomnia, but insomnia that continues for more than a month or six weeks can have a marked effect on your health and general quality of life.