How much sleep do I need?

As the days are at their longest, my sleep is at its shortest and it’s got me wondering about how much sleep I actually need. I have often stated that without the recommended 8 hours I am a zombie, but who recommended those magical 8 hours, and are they right for everyone?

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Research from the University of California, San Francisco in the USA has found that some people have a particular gene enabling them to function well on six hours of sleep a night. But, importantly, the gene is very rare and less than 3% of people have it. The rest of us, it appears, will be unable to cope with six hours. Indeed, the National Sleep Foundation of America recommends that adults aim for between 7–8 hours of sleep a night. How then, did Margaret Thatcher famously get by on only four hours of sleep a night?

The first thing experts will tell you about sleep is that there is no "magic number”, different people have different sleep requirements. Your sleep needs will vary depending on your gender, age, population, diet, lifestyle, and numerous other characteristics. Whilst most experts agree that there is no magic number, there appears to be some debate as to whether people can function optimally on less than seven hours of slumber. The recommended hours of sleep depending on age are listed below and this is thought to be the amount at which people will function at their best and feel energetic throughout the day. If you have less than this amount and find yourself feeling sluggish, perhaps it is best to hit the hay a little earlier. Dr Michael Breus, a clinical sleep expert, suggests that if people have any of the following traits they should go to bed 15 minutes earlier each day until they start to feel a change.

• Daytime sleepiness
• Fatigue
• Difficulty concentrating
• Poor thinking
• Accident-prone
• Other health complications (i.e. weight gain)

By logging how you feel during the day, based on the hours of sleep from the night before, you will be able to calculate your basal sleep need. Unfortunately, one or two late nights or early mornings during the week can mask this basal sleep need due to sleep debt and make us feel like we need more sleep than we really do. If you have an accumulated sleep debt and feel tired, particularly during the mid-afternoon or during the hours of darkness, you can resolve this by ensuring that each night you satisfy your basal sleep need through earlier bedtimes or napping in the daytime. So much for my Sunday morning lie-in making up for the rest of the week then…

Though scientists are still learning about the implications of basal sleep need, research into sleep has shown that sleeping too little can not only inhibit your productivity and thinking ability, but a lack of sleep can lead to serious health consequences such as high blood pressure, heart disease and diabetes, and it has also been linked to an increased risk of accidents whilst driving and psychiatric conditions such as depression and addiction.

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Ok, I am quite happy to get more sleep, but is there a point at which I can overdo it? There does appear to be a link between long hours of sleep and illness or accidents, particularly within low socioeconomic groups, although researchers are not agreed on whether an overdose of sleep is causing these morbidities or whether it is more closely related to the fact that those people on low incomes are less likely to have effective medical care and are more likely to have undiagnosed illnesses.

Dr Kristen Knutson of the University of Chicago, USA, states that currently “…there is no strong evidence that sleeping too much has detrimental health consequences… [but] there is laboratory evidence that short sleep durations of 4–5 hours have negative physiological and neurobehavioural consequences.” Good news for students and teenagers then, but can there really be no consequences for over-sleeping, and if not, is there such a thing as sleeping too long?

Researchers Shawn Youngstedt and Daniel Kripke think so. They have looked at two surveys by the American Cancer Society which assessed the sleep patterns of over a million people. The findings showed that those people who slept seven hours had less health problems after six years than those sleeping both more and less. Further to this, those people sleeping for more than eight hours a night had the highest mortality risk.

The National Sleep Foundation of America conclude that there is no magic amount of sleep that we all need but that in order to determine your basal sleep need you should aim to sleep until you wake naturally, without an alarm clock. If you are unsure where to start with calculating your sleep requirements, try 7.5 hours, this is thought to be the optimal amount of sleep for the average adult.