Normal healthy people of different ages have different requirements for sleep. The fetus also has sleep and waking moments in the mother's womb, but most of the time is in sleep. According to the observation of fetal EEG, REM sleep takes up most of the time.
Newborn babies spend most of their time sleeping, averaging 14-16 hours every 24 hours, about half of which is REM sleep. When newborns sleep, we can clearly see that their eyeballs are moving back and forth rapidly. It is precisely by observing the rapid movement of the eyeballs in newborn sleep that scientists discovered REM sleep. In addition to rapid eye movements, newborns can also see that they often clench their fists, make faces and smile with their fingers or toes moving, which indicates that they are dreaming. Unfortunately, we cannot understand the dreams of newborns. In a word, from the analysis of sleep EEG from fetus to neonate, REM sleep is mainly used, indicating that REM sleep is very important for the growth and development of their central nervous system.
With the growth of children, the sleep time of children will be reduced to about 12 hours by the preschool stage, plus 1 hour of nap. At puberty, sleep is further shortened to 9 to 10 hours, and no longer takes a nap. REM sleep is gradually shortened with age, and its proportion in the whole night sleep is also reduced. Generally speaking, if a child is alert and happy during the day and does not look tired, it probably means that sleep at night is enough.
Adults sleep an average of eight hours. There is a slight difference between men and women. It takes 7 to 9 hours for men and 9 to 10 hours for women. That said, the difference between male and female sleep time actually depends on subjective and objective conditions. For example, in women's pregnancy, due to a large increase in progesterone, the endocrine hormone that maintains pregnancy, pregnant women will sleep more than usual. At ordinary times, women's sleep is also shallower than men's, and they are easy to wake up, so they are prone to insomnia. When menopause comes, insomnia becomes more prominent and becomes a major feature of climacteric syndrome.
The structure of sleep at night in adults has changed accordingly. The total time of REM sleep continues to decrease, and the cycle of REM sleep also decreases, accounting for only about 1/6 of the total sleep at night.
People always think that the elderly only need a small amount of sleep, which is not entirely correct. The sleep quality of the elderly in NREM III and IV phases is obviously reduced. Sometimes there is no NREM III and IV phase, but only NREM I and II phases. The sleep quality is not high, and they are easy to wake up early in the morning. The total sleep time per night is only 5-6 hours. But this does not mean that the elderly only need less sleep time, because the 24-hour sleep EEG examination found that the elderly often have light sleep during the day, perhaps they are in this way to supplement the lack of sleep at night. We often find that the elderly who are reading newspapers, watching TV and listening to music gradually lower their heads, close their eyes, and sometimes even snore gently and drool. This is the shallow sleep of the elderly. They are making up for the lack of sleep at night.
In addition to the different length of sleep required by people of different ages, people of different personalities also have different sleep states. Character is a relatively stable psychological feature in people's attitude and behavior. The formation of character has genetic factors, but more importantly, environmental factors. Genetic factors determine a person's physiological quality. On this basis, he gradually formed his character through learning and life training. People usually divide personality traits into introversion and extroversion. Some studies have found that people who sleep short are extroverted, broad-minded, optimistic and confident, active in work, ambitious in career, and confident in life and future; The study of EEG shows that most of these people are "deep sleep" and "moderate sleep" of NREM. Although the sleep time is short, the sleep quality is high and the daytime work efficiency is high. However, most people who sleep for a long time are introverted, cautious, good at thinking, and have unique views on things, but they tend to think too much. Most people like to complain when they encounter difficulties, and are easily frustrated after setbacks; The EEG study found that most of these people were NREM's "shallow sleep" and "REM".
In a word, sleep is absolutely necessary from birth to death, but the time, structure and content of sleep have quite complex changes due to individual differences.