Occasional lack of sleep is a common experience. Usually, you should be able to overcome the problem by altering your lifestyle, but if you have persistent sleep problems you should consult your doctor (see Insomnia).
Why we need to sleep

Although scientists do not completely understand why people need to sleep, research shows that the body and mind require time to rest and recover from the day's activities. While you sleep, your body undergoes a series of repair processes and conserves energy.

There are two types of sleep: rapid eye movement (REM) sleep and non-REM sleep. During REM sleep, brain activity increases, dreaming occurs, and information is processed to reinforce memory and learning. Non-REM sleep consists of four stages: stage 1 is light sleep, in which you may wake sponta neously, and stage 4 is the deepest, in which you are very hard to wake. Each complete cycle of non-REM and REM sleep lasts about 90 minutes, starting with non-REM sleep. An average sleep cycle is made up of three-quarters non-REM sleep and one-quarter REM sleep.
Sleep requirements

Sleep runs on a daily cycle regulated by an internal clock. Although people tend to sleep at night and are awake during the day, the cycle adapts to individual needs. The amount of sleep needed changes over a person's lifetime and depends on the individual. Newborn babies sleep up to 16 hours a day. Most people sleep an average of 7-8 hours a night, but generally the amount of sleep you need decreases as you grow older. Many people over 60 need only 6 hours sleep a night, although they may take a nap during the day.

Most people can cope with a couple of nights in which they have little or no sleep, without experiencing serious harmful effects on their health. At certain times, such as when you are ill or convalescing, you may find that you need more sleep than you usually have.
Promoting good sleep

The most successful approach to getting a good night's sleep is to have a healthy lifestyle and to establish a regular routine before getting into bed.
A healthy lifestyle

The key lifestyle factors that will help to ensure good sleep patterns are getting sufficient exercise, moderating your alcohol and caffeine intake, and not smoking.

Exercise promotes a sense of calm and well-being by increasing the production of endorphins in the brain (see The benefits of exercise). It also helps to tire you out physically.

Caffeine and nicotine are both central nervous system stimulants and may prevent you from falling asleep. Reduce your caffeine intake during the afternoon and evening. If you smoke, giving up may improve your sleep and also your general health (see Tobacco and health). Alcohol is a sedative (see Alcohol and health), but you should not use it to help you to sleep because alcohol-induced sleep is not as refreshing as normal sleep.
Bedtime routine

By adopting a consistent bedtime routine, you may find it easier to relax and sleep normally. Your routine could include listening to the radio, reading, or practising relaxation exercises. Try soaking in a hot bath 2-4 hours before going to bed or having a warm drink made with milk at bedtime. Try to avoid working late into the evening. Make sure your bed is comfortable and your bedroom is well ventilated, not too hot or too cold, and sheltered from outdoor light.
Dealing with sleep problems

At some time in their lives, most people experience changes in their sleep patterns. Common problems are trouble getting to sleep, waking during the night or too early in the morning, and sleepiness during the day. Snoring is another major cause of sleep disturbance. Sleep problems are often due to stress-associated behaviour such as drinking more alcohol than normal or working until late at night.

If you have a sleep problem, examine your lifestyle to see if a change in activity or behaviour could account for it. If you cannot sleep, get out of bed, walk around, or read until you feel sleepy. Try to establish regular times for sleep and waking up. If you have a bad night, try not to sleep during the next day, but if you feel tired a nap of up to 20 minutes may improve your alertness.

If you continue to have difficulty sleeping, you should see your doctor. Your problem may be a symptom of an illness, such as depression, or a side effect of medication.