Facts About Sleep

Facts & Myths ,

Sleep is essential for everyone, we spend about one-third of our lives in bed. A healthy sleep helps us to recharge our batteries, both mentally and physically. A good night’s sleep is the best way to cope with daily stress, work more efficiently and fight off illness.

A: Many people think that sleep is a passive and unchanging process. In fact, only the physical body rests during sleep, the brain remains active. There are two basic states of sleep, rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep, which the brain organizes in a regular and cyclic manner throughout a night of sleep. Sleep usually begins with 80 minutes of NREM sleep followed by 10 minutes of REM sleep with this cycle being repeated four to six times throughout the sleeping period. NREM sleep is characterized by a slowing down of the brain and body functions, e.g. the heartbeat, blood pressure and breathing are slower, and the whole body muscles are relaxing; REM sleep appears in brief intervals with increased activity in the brain and body, the body’s sensational responses will be further declined, the muscles become more relaxing, but the heartbeat, blood pressure and body temperatures are increased. If the sequence is interrupted, such as by external stimuli, it will affect the quality of sleep. (See below sleeping chart of a young adult.)

Sleeping chart of a young adult

Sleeping chart of a young adult

Generally, the NREM sleep and REM sleep occur alternatively during a night of sleep, which runs four to six cycles, and each cycle lasts for about ninety minutes. The NREM sleep will dominate the first half period, and the REM sleep will be more frequent in the later half period. Exercise before sleep can elongate the time of REM sleep, and promotes a deeper sleep condition.

A: Although the precise functions of sleep remain unclear, sleep is important for normal physical and mental functioning. Sleep is an essential process for the body to repair itself, synthesize and replenish substances, and cleanse the metabolic wastes. We all recognize the need for sleep, lack of sleep will lead to difficulty in concentration, memory lapses, low energy, fatigue and emotional instability. In the long term, sleep disturbances are associated with serious illnesses such as hypertension, heart disease, stroke, diabetes, obesity, mental disorders, mental impairment and even growth retardation in children. Studies have demonstrated that brain activity declines significantly after 24 hours of sustained wakefulness, there is also a decrease in body temperature as well as a decline in general immunity.

A: The amount of sleep needed varies from person to person, and changes throughout our life. Generally, newborns sleep about 16 to 18 hours a day; preschool children sleep between 10 and 12 hours; school-aged children and teenagers sleep at least 9 hours, while most adults sleep 7 to 8 hours on average. However, many people may need less or more than the average hours but still feeling completely refreshed afterward. The most important criteria for adequate sleep are sleep should be uninterrupted; you should feel alert and refreshed on awakening, and there should be no drowsiness even when engaging in boring activities. If you feel drowsy while awake, you may not have had enough quality sleep.

A: On average, we need 7 to 9 hours sleep per day for optimal heath. When the daily sleep hours are less than an individual’s needs, a “sleep debt” develops. This means the loss of sleep will eventually need to be repaid with additional sleep over the coming nights. Our body seems unable to adapt to sleep less than it needs. When the sleep debt becomes too great, it can lead to impaired body functioning, your daily performances, mental responses and even emotions become disturbed significantly. Caffeine and other stimulants cannot act as substitutes for sleep; they can only counteract some effects of sleep deprivation.

A: There is no evidence to show that older people need less sleep than younger people. In fact, older people don’t need less sleep, but they often get less sleep. While sleep patterns change as we age, older people tend to spend less time in the deeper, restful stages of sleep. They are more easily awakened by light, noise, or pain. For elderly people, it takes longer to fall asleep, and the frequency and duration of overnight arousal increase. Therefore, they should stay longer in bed to ensure they have enough rest for ordinary everyday functioning.

A: Not true. Our body has an internal biological clock to regulate the sleep-wake cycle, that functions according to a normal day-night schedule. Th clock tells the body when to sleep and wake up, and also affects many important functions in the body. Traveling across time zones or working night shifts will confuse the body’s sense of time that makes sleep difficult and inhibit some necessary body functions. The biological clock can be reset, but only through gradual adjusting one to two hours per day at best, therefore it takes some time for our body to adjust to a new time schedule. To reset the sleep cycle, and get better rest and more, some measures are helpful, such as sleeping in a dark and quiet room, getting exposure to bright light at night time, and changing eating and exercise patterns.

A: On average, we spent about two hours dreaming every night and mostly during the REM sleep, when the brain is most active. Experts believe that dreaming helps exercise certain brain functions, promote learning and memory, and even solve problems that require much concentration. We cannot remember dreams, because the brain system responsible for creating memories may shut down during REM sleep. We only remember dreams that occur just before awake.

Nightmares that occur in children and adults are associated with stress, traumatic experiences, emotional problems, drugs or illness. Scientists still know little about how or why we have nightmares, however, being tired, inadequate sleep, irregular sleep routine, stress or anxiety have found to increase the risk of experiencing nightmares. Most nightmares are a normal part of coping with changes in our lives.

A: Generally, if you find it difficult to fall asleep, cannot stay asleep through the night, wake up too early, have a hard time waking up, or are very tired during the day, you may suffer from a sleep disorder. When you experience the following symptoms for a month or more, it is recommended that you seek professional advice:

  • take over 30 minutes to fall asleep every night;
  • wake up several times at night and cannot go back to sleep;
  • wake up too early in the morning;
  • have vivid, dreamlike experiences while falling asleep;
  • feel sleepy, have frequent naps or fall asleep at inappropriate times during the daytime;
  • struggle to stay awake when inactive, such as while watching TV or reading;
  • have difficulty in paying attention or concentrating at work, school or home;
  • become emotional very easily.

 

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