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We do not know why exactly we need sleep. Sleep is often described as a “rest,” but it is not true; our brains actively work without lowering energy consumptions during sleep. Our brains work on consolidating memories, erasing and storing information, and restoring functions while we sleep. However, no one can exactly answer the question of why we need to lose consciousness during sleep. It is best to have sufficient sleep every day since chronic sleep deprivation would affect our daily performance and increase the risk for health issues.

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The required amount of sleep defers from person to person. However, epidemiological studies indicate that vast majority of adults needs between 6 – 8 hours of sleep. It is a sign that you need more sleep if you: (a) feel tired and sleepy during the daytime; (b) sleep significantly longer (＞2 hours more) in weekends than weekdays. The only way to find out the sufficient length of sleep for yourself is by examining how you feel with different sleeping hours and seeing if there are any signs of sleep deprivation.

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It is important to create a comfortable environment for sound sleep. You may be able to improve the quality of your sleep by: 1. Try to make your bedroom as dark as possible. 2. Make sure it is a quiet environment. 3. Maintain a pleasant temperature and humidity of your bedroom. Moreover, it is important not to drink too much water before you go to bed, not to consume caffeine, not to drink too much alcoholic beverage, and not to do anything that would excite you emotionally. Having a routine before sleep would also be beneficial.

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With age, a lot of people start to have trouble keeping themselves asleep. It is normal for people who are in their middle age (40-50 years old) and above to wake up in the middle of the night. You do not have to worry too much if you are only waking up once or twice for a short period of time; however, it might be a good idea to consult a doctor that specializing in sleep medicine if it affects your daily activities, if you keep waking up 3-4 times or more during the night, or if you can not return to sleep for a long time once you wake up during the night.

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Cognitive behavioral therapy for insomnia (CBT-I) is an effective therapy. There is a manual on the website that could help you. However, it’s best to consult a doctor specialized in sleep medicine if it doesn’t get any better.
CBT-I：http://uwaims.org/alamedacounty/trainingmaterials/032513/cbtimanual.pdf

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You do not have to worry too much if you snore a little; however, if your bed partner notices that your breathing is stopping periodically, you are suffering from sleep apnea syndrome (SAS). It could greatly affect the quality of your sleep and increase your risk for diseases like stroke. It is best to get checked by a specialist if you think you have SAS. Dr. Makoto Sato of IIIS is a specialist in SAS, and suggests people to sleep on their side while hugging a pillow (this is because snoring occurs when you sleep on your back and your tongue drops down to your throat). Obesity is not the only reason for snoring but losing weight could alleviate the symptoms.

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The function of dreaming is still not well understood. There are theories suggesting that we dream to rehearse prospective negative experience or prepare ourselves for a conflicting state of mind that we could encounter. However, these theories are not scientifically proven yet; we still do not know why we dream.

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Short sleepers are quite rare, much rarer than people expect. It is likely that less than 1% of people is a “true short sleeper” who needs less than 5 hours of sleep per day, although no large-scale epidemiology has been conducted yet to figure out how many true short sleepers exist. There are people who claims themselves as short sleepers, but they likely do not realize they are short in sleep. Insufficient sleep would decrease daily performances and health problems. It is important to have enough sleep you need.

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Narcolepsy is also known as the “dozing-off disease.” People with narcolepsy readily and often suddenly fall asleep in inappropriate times during their day. Many of them also experience a sudden muscle weakness often triggered by positive emotion. Scientifically, it is a disorder in which the switch to retain wakefulness becomes unstable. Approximately 1 in 1,000-,2000 people is thought to have this disease. Drs Yanagisawa and Sakurai found the neuropeptide orexin, and its deficiency is known to cause narcolepsy. IIIS has been trying to develop a medicine that remedies narcolepsy.

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As an example, Professor Mitsuo Hayashi of Hiroshima University implemented an academic course for freshman students, in which they are asked to keep a sleep diary to improve their sleep patterns. Students who took this course experience a vastly improved mental performance, to the extent that they claim they are living in a different world. Majors to improve sleep are being implemented in the community level in parts of the United States and European countries. One example is Start School Later programs, where they delay the starting time of school as much as by 2 hours. Our circadian clock is know to be delayed nearly 2 hours from poberty to adult ages, making it difficult for them to get up early or go to sleep early. Delaying the starting time of school provides an environment for students where they can concentrate better in their classes.