It turns out we actually need NINE hours of sleep, not eight

How much sleep do you get each night? I can hazard a guess that it's probably not nearly enough – or good enough quality.

Why? Because many of us are walking around with a chronic "sleep deficit" – and feeling tired, lacking energy and irritable as a result.

I know I need nine hours of sleep a night in order to function. This might sound like a lot – especially when there is so much to fit into the day – but it really isn't. It's actually pretty normal.

Before the invention of electricity, people slept for approximately nine to ten hours per night.

Now, on average, people in the Western world sleep for approximately seven to nine hours per night, reports Daily Mail.

So in less than a couple of centuries, our sleeping habits have changed dramatically.

Today, therefore, we are having less than the amount of sleep we need, suggesting that most of us have built up a "sleep debt".

SO HOW MUCH SHUT-EYE SHOULD WE BE GETTING?

We all have our own natural thresholds concerning the number of hours' sleep we need.

Some people need more, others less. If we don't get enough sleep, we develop a 'sleep debt' and, like all debt, this needs to be repaid.

As a society, our sleep debt is partly a direct consequence of our 24/7 lifestyle.

People simply don't sleep long enough. We tend to stay up late watching television or doing other activities, and delay the time we go to bed.

This is OK if you can catch up with your sleep at the weekends, although it seems a shame that you spend a good portion of your quality free time sleeping when you could simply have gone to bed earlier in the week!

Even then, you may not catch up on the amount you need.

Sleep researchers believe many people in Western societies are chronically sleep-deprived, and it is easy to see why.

In the USA, for example, the number of people who report they sleep six hours or less most nights increased from 13 percent in 1999 to 20 percent in 2009.

This is worrying considering that sleep deprivation is associated with reduced alertness, task performance, decision-making capacity, occupational injuries and, of course, many accidents.

There are long-term effects, too.

Sleep is considered to be the most important recovery mechanism available to man – and some people think it may be more influential in terms of longevity than diet, exercise or genetics.

DON'T FEEL GUILTY ABOUT NEEDING NINE OR TEN HOURS SLEEP

Although sleep need varies between individuals – some people can get by on relatively little – most people need 7.5 to 8.5 hours a night.

Don't feel guilty about needing more than eight hours' sleep. There is no absolute set sleep time and people do vary.

It always amazes me that for some reason, many people I speak to don't make the link between going to bed late and feeling tired in the mornings. Listen to your body. If you are tired during the day, try going to bed a little earlier.

Remember the old saying: an hour before midnight is worth two hours after. I guess in their own minds, to many people, 11.30 may not seem that late, but it is if you are tired and fighting the natural urge to sleep.

Sometimes this creates issues in relationships where one partner needs lots of sleep and the other not so much.

Remember, one of the greatest scientific minds of all time, Albert Einstein, was said to sleep around ten hours a night. This was unless he was working on a particularly hard topic – then he would need 11 hours!

WHY I DON'T BELIEVE IN NAPPING…

In the 1990s, the idea of the power nap was born, the idea being that a short nap, between 15-30 minutes, restores wakefulness and promotes performance and learning.

Unless absolutely essential – that is, if you feel too tired to function safely – I think napping should be avoided. People only nap because they have sleep debt – and napping should not be used to supplement abnormal sleep.

Also, there is evidence that workers actually sleep worse on Sunday evenings if they take a nap during the day. Again, these people tend to nap because they have accumulated a sleep deficit.

Furthermore, napping or sleeping for more than 30 minutes appears to be associated with feeling groggy upon waking – which can only make you feel worse.

…AND WHY YOU SHOULD NEVER FALL ASLEEP ON THE SOFA

Many people who have difficulty switching off from work also have trouble with sleeping because they find themselves thinking about and going over and over work issues while in bed. This can be difficulty in getting to sleep, maintaining sleep, or waking up too early in the morning and not getting back to sleep.

Yet many people say they have no problem nodding off on the sofa earlier in the evening.

Rachel, for example, came to see me because she had difficulty sleeping and said that she would lie awake and her mind would go over and over.

She told me that she didn't understand it because she could easily fall asleep on the sofa in the evenings while watching television but not when she went to bed.

She said she would lie in bed getting more and more frustrated and she would start worrying that if she didn't get enough sleep she would not be able to function at work the next day. She also said that she noticed she became very irritable.

Rachel's sleeping problems were quite easy to solve. Her main issue was napping in front of the TV; this suggested to me that she could fall asleep quite easily. The reason she couldn't get to sleep in bed later in the evening was because she was by then less tired and her mind would start to wander.

We developed a sleep hygiene routine which meant putting an end to her evening napping and we also worked on a plan for her to develop a regular bedtime routine.

Within a couple of weeks Rachel was no longer complaining about her mind wandering at bedtime, and she was sleeping much better and (to the relief of her partner and friends) was less irritable.

Other sleep problems and sleep disorders may not be related to the timing of sleep but to work or family-related stress or worries.

In fact, one of the major causes of sleep onset latency – how long it takes to fall asleep – is worry. How we think and feel affects how long it takes to fall asleep.

THE PLAGUE OF WAKING UP DURING THE NIGHT

We have shown in numerous studies that people who have difficulty switching off from work during the evening and at bedtime are on average four times more likely to report problems in trying to fall asleep - and seven times more likely to report restless sleep during the night compared to those who are able to unwind during their evening leisure time.

It has also been estimated that between 29 and 45 percent of the adult population may experience some form of sleep disturbance.

There are many reasons for this but perhaps the invention and the availability of electricity is a contributory factor as we are now exposed to artificial light and stimulation in the evening.

In the short-term, traditional herbal remedies that include ingredients such as Valerian and Passionflower – both used as sleep aids for hundreds of years – can be a good, safe solution. However, always look for products with a THR (traditional herbal remedy) which is a guarantee of quality and authenticity.

Think about the questions below in terms of your sleep over the previous few nights

HOW DID YOU SLEEP THIS WEEK?

Source: Mark Cropley

By completing the table, you should be able to see whether your sleep is disturbed throughout the night (question one) or whether your difficulties specifically relate to sleep onset issues (questions two, three, four and five).

Sleep onset insomnia is trouble falling asleep, and sleep maintenance insomnia is trouble staying asleep.

People who have sleep maintenance insomnia may find they wake several times during the night. Both types can leave you feeling unrefreshed in the morning (question 6).

A total score over the whole table of more than 18 over a number of nights suggests that you do have a sleeping issue.

Everyone wakes up during the night but most of us are not consciously aware when it happens and we normally fall back to sleep without much difficulty.

Moreover, we don't even remember waking up. These short periods of awakening don't constitute a sleep issue and rarely trouble us.

If, however, something has been bothering us at work, we may find ourselves waking up during the night and replaying the event over and over in our minds. Even if we only wake to use the bathroom, we may start thinking about work issues.

• The Off Switch: Leave on time, relax your mind but still get more done by Mark Cropley; Virgin Books

This article was first published on Daily Mail and is republished here with permission.