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What is sleep debt?
"Humans require a certain amount of sleep, and if their sleep duration is shorter than that, the deficit accumulates. In other words, a sleep debt is incurred."
This is a concept called "sleep debt" that Professor William C. Dement, the first director of the Stanford University Sleep and Circadian Rhythms Institute, the world's leading sleep research laboratory, began using in the 1990s.
Although the term "sleep deprivation" is also widely used, sleep researchers use the term "sleep debt" to describe a state of insufficient sleep.
When insufficient sleep becomes chronic, it leads to sleep debt, which has a significant impact on both the brain and body. This accumulated sleep deficit, which is difficult to resolve and silently builds up serious negative factors, is precisely what "sleep debt" is.
The Current State of Sleep Debt in Japan
Japan has the highest number of people with "sleep deprivation syndrome", suffering from sleep debt, in the world. This is likely due in large part to the unique Japanese value system that considers it a virtue to prioritize other activities over sleep. However, research shows that compared to other countries, Japan has overwhelmingly shorter average sleep durations and a greater discrepancy between desired and actual sleep times.
Can "catching up on sleep" truly resolve sleep debt?
For this reason, many people will "catch up on sleep" on weekends to repay their accumulated sleep debt. However, in reality, this merely supplements the deficit, as sleep cannot be saved or stored. Repaying sleep debt is extremely difficult, and simply increasing sleep time temporarily is not enough.
While there are rare individuals known as "short sleepers" who can function perfectly well with minimal sleep, research shows that most of them have a genetic predisposition, making them different from the average person. Not everyone can become a short sleeper through effort, and doing so is more likely to be detrimental to one's health.
What happens when sleep debt accumulates? What is microsleep?
Sleep debt makes people more susceptible to "microsleep," which is a momentary nodding off of the brain. As a defense mechanism against sleep debt, the brain temporarily stops working and falls asleep for 1 to 10 seconds.
What's frightening is that the person has no subjective awareness of it. If you were to experience microsleep while driving, the recent accidents caused by dangerous driving would not be someone else's problem. This can happen to anyone with sleep debt. While everyone is aware of the dangers of drunk driving and it is legally prohibited, most people are unaware of the dangers of driving while sleep-deprived.
Sleep and wakefulness are two sides of the same coin. Good sleep leads to good wakefulness, and good wakefulness leads to good sleep.
How to resolve sleep debt?
Sleep debt can only be resolved by sleeping. Some people may think that if the quality of sleep is good, short sleep durations are not a problem, but that is not the case.
Ideal sleep is achieved only when three conditions are met: "sufficient quantity (duration)," "good quality sleep," and "waking up refreshed."
