Will staying up late for a long time really make you stupid?

Author: Li Cuiluan, deputy chief physician of Shandong Mental Health Center

Reviewer: Mi Guolin, Chief Physician, Shandong Mental Health Center

1. The important role of healthy sleep

About one-third of a person's life is spent sleeping. Sleep is closely related to individual survival and development, biological evolution, and species reproduction.

Good sleep is also one of the health standards recognized by the international community and plays an important role in the human body. Healthy sleep can relieve the fatigue accumulated from a day's work and study, restore physical strength and energy; it can enhance the body's immune function; it can promote growth and development; it can consolidate daily learning and memory abilities. In addition, the metabolic products that are constantly accumulated in the brain during work while awake during the day can also be efficiently cleared during sleep.

Sufficient sleep time is one of the important factors for sleep health. The specific length varies from person to person. Generally speaking, the younger the age, the more sleep you need. Most healthy adults need 7 to 8 hours of sleep a day.

2. Staying up late steals healthy sleep

As the pace of life quickens, "staying up late" has become a behavioral phenomenon that is often heard or done in modern life, and more and more people are losing the normal sleep time required for health.

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There are many reasons for staying up late, one is passive staying up late, the other is active staying up late. The former refers to staying up late due to work or study needs or passively choosing to stay up late after "insomnia". The latter is a lifestyle that people, especially young people, actively choose. After a busy day of study and work, the night becomes a rare private time for oneself. "Reluctance to sleep" has become the common reason for most people who actively stay up late. They will use this rare time to watch TV series, play games, party, etc., so that they can relax temporarily.

However, when healthy sleep is stolen, adverse consequences follow, one of the most important of which is damage to cognitive functions such as memory.

3. Staying up late for a long time will really make you stupid

1. Staying up late will affect memory consolidation

Experiments have repeatedly confirmed that memory consolidation depends on sleep after learning. If you fall asleep immediately after studying hard for a period of time, it will strengthen the content and memory of what you have learned. Among them, different sleep periods play different roles in memory consolidation. Slow-wave sleep is more important for explicit memory (dependent on the hippocampus), while rapid eye movement sleep (REM sleep) is more important for implicit memory (not dependent on the hippocampus).

In recent years, the results of studying the process of sleep and memory consolidation using electrophysiological and brain functional imaging techniques have shown that hippocampal neurons during sleep can reproduce hippocampal activity during wakefulness, that is, brain activity during sleep transforms newly acquired and encoded information during wakefulness from traces of unstable memories into more stable memory patterns. This kind of memory consolidation is essentially restarting the processing of new information in the neural circuits that encode it, which is called reactivation or replay. If the reactivation process is strengthened, the effect of memory improvement is more significant. On the contrary, if the reactivation process of hippocampal neurons during sleep is blocked, memory will be impaired.

Neural activity reactivation has the following characteristics, let’s take a look.

(1) Mainly occurs during slow-wave sleep.

(2) It is more likely to occur within the first few hours after learning.

(3) It occurs in only a minority of the recorded neurons.

(4) The reactivation sequence is consistent with the awakening period.

(5) Unlike the encoding phase, the reactivation phase is accompanied by noise, inaccurate information processing, and faster speed.

Staying up late causes people to lose slow-wave sleep and REM sleep, which has a great impact on the consolidation of both explicit and implicit memory.

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2. Staying up late for a long time increases the risk of dementia

During sleep, the brain can efficiently remove metabolic products that accumulate during the day, thereby restoring brain vitality. During daytime wakefulness, waste products from cell metabolism accumulate in the intercellular fluid. During sleep, cerebrospinal fluid flows into the brain tissue along the periarterial space, constantly exchanging with the interstitial fluid in the brain, and carrying metabolic waste products from the intercellular fluid to the perivenous space, which is then discharged from the brain.

The state of the intercellular space is very different when awake and asleep, which is manifested in two aspects: first, the volume of the intercellular space accounts for 14% of the total brain volume when awake, and increases to 60% during normal sleep, thus significantly increasing the flow of cerebrospinal fluid; second, the flow of cerebrospinal fluid when awake is limited to the surface of the brain, while its flow expands to the deep layers of brain tissue during sleep. Because of the above two factors, the beta-amyloid protein produced by brain metabolism can be efficiently cleared from the brain during sleep. Staying up late for a long time can affect the effective removal of beta-amyloid protein, and the accumulation of this substance in the brain is related to the onset of "dementia". Studies have found that when the sleep time is less than 7 hours/day, the risk of dementia will decrease by 27% for every additional hour of sleep time.

Therefore, in order for us to have a smart brain, please refuse to stay up late for a long time, maintain a healthy lifestyle and get enough sleep.

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