How Much Sleep Do You Really Need?

Some people insist they are fine on five hours. Others feel wrecked without nine. So how much sleep does a person actually need?

The honest answer has two parts. There are clear recommendations for each age group, based on a large body of research. And within those ranges, people do differ. This guide gives you the figures and then explains how to work out where you sit.

The short answer

For adults, at least seven hours a night.

The US National Heart, Lung, and Blood Institute (NHLBI) says that experts recommend adults sleep between 7 and 9 hours a night. The US Centers for Disease Control and Prevention (CDC) puts it as 7 or more hours for adults aged 18 to 60. The NHS says that adults need 7 to 9 hours on average.

Recommended sleep by age

These are the CDC's recommended daily amounts. For younger children, the totals include naps.

Two things stand out. Children and teenagers need far more sleep than adults, which is worth remembering when a teenager is hard to wake. And the need for sleep falls only slightly in later life: adults of 65 and over are still advised to get seven to eight hours.

Why the amount matters

Sleep affects almost every tissue and system in the body. The US National Institute of Neurological Disorders and Stroke notes that without sleep you cannot form or maintain the pathways in your brain that let you learn and create new memories, and that lack of sleep makes it harder to concentrate and respond quickly.

The NHLBI states that adults who sleep less than 7 hours a night may have more health issues than those who sleep 7 or more.

The CDC lists what enough sleep does for you. It can help you:

• get sick less often;
• stay at a healthy weight;
• reduce stress and improve your mood;
• improve your heart health and metabolism;
• lower your risk of type 2 diabetes, heart disease, high blood pressure and stroke;
• lower the risk of motor vehicle crashes;
• improve your attention and memory.

The mention of road crashes is a reminder that the effects of short sleep are not only long term. Drowsiness slows reactions the same day.

Can you sleep too much?

Occasionally needing more sleep is normal. The NHLBI says that sleeping more than 9 hours a night is not necessarily harmful, and may be helpful for young adults, for people recovering from a period of too little sleep, and for people who are ill.

Regularly needing far more sleep than the recommended range, and still feeling tired, is different. That can be a sign of an underlying problem and is worth raising with a doctor.

Seven, eight or nine? Finding your own number

The recommended range for adults spans two hours, and people really do differ within it. Three ways to work out what you need:

Notice how you feel in the day. This is the simplest test, and the one the NHS points to: you probably do not get enough sleep if you are constantly tired during the day. If you wake without too much struggle, stay alert through the afternoon and do not rely on caffeine to function, you are probably getting enough.

Look for the signs of too little. These include needing an alarm to drag you out of deep sleep every morning, dozing off in meetings, on the sofa or on public transport, sleeping much longer at weekends, irritability, and difficulty concentrating.

Run a simple experiment. When you next have a week or two without early starts, go to bed at the same time each night and let yourself wake naturally. After the first few days, during which you may be catching up, the amount you settle on gives you a rough idea of what suits you.

It is not only about hours

You can spend eight hours in bed and still wake unrefreshed. The CDC describes quality sleep as uninterrupted and refreshing, and notes that it is not just about how many hours you sleep, but how well.

Signs of poor sleep quality, according to the CDC, include:

• trouble falling asleep;
• repeatedly waking up during the night;
• feeling sleepy or tired even after getting enough sleep.

Timing matters as well. Sleep works best when it happens at a consistent time, in line with your body clock. Eight hours taken at a different time each night is less restorative than the same eight hours kept regular.

Why "I'm fine on five hours" is usually wrong

It is easy to get used to feeling tired. After weeks of short sleep, an under-slept state can start to feel normal. Feeling used to it is not the same as being unaffected.

Individual needs do vary. But the recommendations exist because, for adults in general, regularly sleeping less than seven hours is associated with more health problems than sleeping seven or more.

What about catching up at weekends?

A long lie-in can ease some of the tiredness after a short week, but it is a poor strategy. It shifts your body clock, which makes it harder to fall asleep on Sunday night, and so the cycle repeats.

The NHLBI advises keeping the same sleep schedule on weeknights and weekends, and limiting the difference to about an hour. If you are short of sleep, going to bed a little earlier works better than getting up much later.

Short naps can help too. The NHLBI suggests that adults nap for no more than 20 minutes, and earlier in the afternoon if night-time sleep is a problem.

If you are not getting enough

Sleep is often the first thing that busy people squeeze out of their schedules, as the NHLBI observes. The first step is simply to give yourself enough time: count back from when you need to get up, and protect that bedtime as you would any other appointment.

Then look at the habits around it:

• keep a regular wake-up time;
• get daylight and activity during the day;
• stop caffeine after lunch;
• wind down for an hour before bed;
• keep the bedroom quiet, dark and cool.

Simple habits for better sleep sets these out as an evening routine, and Sleep hygiene explained covers the reasoning.

The figure to remember

If you are an adult, aim for at least seven hours, at about the same time each night. Then let your days tell you whether that is enough. If you are alert and steady without effort, it is. If you are not, try giving yourself a little more before you look for any other explanation.