Adults usually sleep for 7-9 hours, and the human body requires 7-9 hours of sleep every night.
Newborns sleep 16 hours a day on average, and the sleep time of infants is gradually shortened, and they sleep about 9 ~ 12 hours at the age of 2. The sleep time of adults varies from person to person, generally ranging from 6 to 9 hours, and it is generally considered that 7 and a half hours is appropriate. But old people usually only sleep for six hours. According to EEG analysis, the heterogeneous sleep of newborns accounts for about 50% of the total sleep time, and soon enters the heterogeneous period after falling asleep, accounting for about 20% of adults and less than 20% of the elderly. In adults, those who sleep less than 15% or more than 25% are considered abnormal. Similarly, the fourth phase of slow wave phase decreases with age. As for the cycle of sleep and awakening, newborns sleep about 5-6 times a day, infants gradually decrease, and school-age children sleep about 1-2 times a day. Some old people have returned to the habit of sleeping several times a day.
The default "sleep time" of "biological clock" is "wake up" 6-8 hours after sleep; And when to "sleep" is not the most important. As long as you "sleep", those "physiological activities" that will happen after sleeping will still be carried out, or: as long as you have enough "sleep time", no matter when you start sleeping, it will not affect your "health"; "Work and rest time" is just a "habit" and can be changed at will. Of course, it takes some time to form a new habit, usually 3-6 days, so it is best not to alternate this habit too often.
Sleep time varies from person to person. Although the average sleep time of adults is eight hours a day, in fact, adequate sleep does not depend on the length of time, but on whether you can reach a state of deep sleep. Experts suggest that sleep time should generally be kept at 7 to 8 hours, which varies from person to person. If you really fall asleep quickly and deeply, and generally don't dream or dream less, sleeping for 6 hours can completely restore your energy, of course. However, those who fall asleep slowly and shallowly, sleep more, and often dream more, even if they sleep for 10 hours, their spirits are still difficult to refresh themselves. It is not good for their health to get effective sleep through various treatments.
deep sleep
Generally, it is measured by the decline of physical activity and sensory sensitivity. In addition, some physiological indexes, especially the awakening threshold, also indicate that the third and fourth stages of slow wave phase are deep sleep. As for the depth of heterogeneous sleep, it is difficult to judge, because it is not only manifested in the relaxation of muscle tension, but also often turns over all over, and the muscles of the face and fingers twitch. Sensually, it is difficult for a sleeper to be awakened by external stimuli, but when the stimuli have special meanings or are related to the contents of his dreams, he will think that this is the first time in his dreams, and it is easy to wake up after being stimulated more than once. These contradictions show that during heterogeneous sleep, an active process in the brain can cut off its connection with external stimuli. If judged by the activity of autonomic nervous system, heterogeneous sleep is closer to awakening state. If the sleeping person is woken up at this time, he will say that he is sleeping. On the other hand, waking him up in the slow wave stage means that he doesn't sleep well. It is speculated that this subjective sleep consciousness may be related to his dreams. To sum up, it is difficult to accurately measure the depth of sleep, and the trend is to regard out-of-phase and slow-wave phase as two independent States.
Some autonomic nervous activities change with the development of sleep process, and there seems to be little correlation between them. For example, the body temperature gradually drops from sleep, reaches the lowest point in 5-6 hours, and then gradually rises. It has been suggested that oral materials can still be learned during sleep, but the analysis of EEG proves that sleepers are actually in a hazy state. Sleepwalking mostly occurs in the second stage of slow-wave sleep, while sleepwalking occurs in the fourth stage of slow-wave sleep without exception, both of which are generally irrelevant to the content of the dream.