What is “sleep debt”? Solved by improving sleep quality instead of sleeplessness

“Sleep debt” accumulates unnoticed due to lack of sleep and deterioration of sleep quality. It is noted that this debt increases the risk of dementia, cancer, lifestyle-related diseases, etc. Seiji Nishino, Professor of Psychiatry, Stanford University School of Medicine, will teach you how to get good quality sleep without building up sleep debt.

What is "sleep debt"?

Table of contents

  • Interviewee: Profile of Mr. Seiji Nishino
  • What is sleep debt? Expert Seiji Nishino explains!
  • Sleep Debt Checklist
  • Know the importance of sleep and its health benefits
  • What are the health implications of optimal sleep duration and sleep debt?
  • What is the key to improving the quality of sleep to eliminate sleep debt?
  • Remember! 8 Ways to Eliminate Sleep Debt
  • Snoring, drowsiness… beware of diseases that lead to sleep debt!
  • Held on December 9, 2022! <Online> Akiko Yamashita’s “Rejuvenating Sleep” Lecture

Interviewee: Profile of Mr. Seiji Nishino

Seiji Nishino

Nishino Professor of Psychiatry, Stanford University School of Medicine. He is the director of the University’s Sleep Biorhythm Research Institute (SCN Lab). He is a doctor, doctor of medicine. His book “Stanford’s Best Sleep” (published by Sunmark Publishing) has sold over 300,000 copies, and a comic version is also on sale. He also commented on sleep problems of women, children and the elderly in “Habits of Sound Sleep Taught by a Stanford University Professor” (published by PHP Shinsho). Author of “Sleep Disorders: Overcoming Modern National Diseases with the Power of Science” (published by Kadokawa Shinsho).

What is sleep debt? Expert Seiji Nishino explains!

What is sleep debt

Difficulty falling asleep, waking up repeatedly in the middle of the night, feeling unrefreshed when you wake up in the morning… Such a person may have a “sleep debt.”

Sleep debt is literally the accumulation of sleep debt. Seiji Nishino, a professor of psychiatry at the Stanford University School of Medicine and director of the Institute of Sleep Biorhythm Research at the same university, said, “Daily sleep deprivation accumulates without us noticing, and damages the brain and body. This debt comes not only from short sleep duration, but also from poor sleep quality.”

Sleep is said to change with age. “Especially after menopause, the quality of sleep in women tends to decline. Since female hormones decrease, body temperature regulation and sleep itself are likely to be affected,” says Nishino.

If you think you’re getting enough sleep but still feel tired in the morning or feel very sleepy during the day, it’s a sign that the quality of your sleep is declining. Also, be careful of people who oversleep more than usual on holidays. “If you sleep more than two hours more than usual, it’s a sign that you’ve accumulated a lot of sleep debt,” says Nishino. Well, are you okay? First, check the following checklist.

Sleep Debt Checklist

Check for sleep debt

If even one is true, it might be sleep debt?

  • Takes over 30 minutes to fall asleep
  • Waking up more than 5 times during the night
  • tired when i wake up in the morning
  • Feeling unmotivated and sleepy during the day
  • Waking up late by 2 hours or more on holidays
  • often irritated

Know the importance of sleep and its health benefits

The important role of sleep and its health benefits

Sleep has many health benefits. For example, resting the brain and body that has been active during the day, consolidating memories, or conversely erasing unpleasant memories, balancing hormones such as growth hormone, and strengthening immunity to prevent infections and cancer Keep diseases such as away, etc. According to recent research, it also works to remove waste products from the brain.

“For example, in Alzheimer’s disease, large amounts of senile plaques are deposited in the brain. The cause of this is a substance called amyloid β, and it is known that the action of removing this is greatest during sleep.” Mr. Nishino. It’s brain cleaning time, so to speak, to discharge substances that are no longer needed.

[5 major missions of sleep]

  1. give your brain and body a rest
  2. organize and consolidate memories
  3. adjust hormonal balance
  4. Boost your immune system and ward off illness
  5. Eliminate waste products from the brain

What are the health implications of optimal sleep duration and sleep debt?

Sleep debt is what interferes with the way sleep is supposed to work. When this debt builds up, it causes a lot of damage to the brain and body. It is said that the death rate will rise.

“In a large-scale study in the United States, the lowest mortality rate was found in people who slept seven hours. On the other hand, those who slept extremely short or long hours had a 1.3 to 1.4 times higher mortality rate (graph (See ).In other words, it was found that the mortality rate increases when the sleep time is too much or too little.In addition, the risk of obesity, diabetes, lifestyle-related diseases such as hypertension, cancer, dementia, etc. It is reported that it will increase.” (Mr. Nishino)

The cost of sleep debt is so high. However, post-menopausal women generally tend to sleep less.

“There is no need to stick to 7 hours of sleep because there are large individual differences, but it is more important to get good quality sleep that suits you,” says Nishino. Improve your sleep quality and start living without sleep debt!


What is the key to improving the quality of sleep to eliminate sleep debt?

The Key to Better Sleep to Eliminate Sleep Debt

Don’t accumulate sleep debt, or pay off existing sleep debt. What you want to achieve is quality sleep. According to Mr. Nishino, the key to improving the quality of sleep lies in the 90 minutes before you start sleeping.

“There are two types of sleep: non-REM sleep, in which both the brain and body are asleep, and REM sleep, in which the brain is awake and the body is asleep. lasts about 90 minutes.This is also the time when the most growth hormones, which promote metabolism and contribute to health and anti-aging, are secreted.The quality of sleep depends on how deeply and soundly you sleep in the first 90 minutes. It really depends.”

So to speak, “golden 90 minutes”. If you can get this, you will wake up refreshed in the morning, and you will not be bothered by sleepiness during the day. Conversely, if the quality of these 90 minutes is not good, no matter how long you sleep, you will not feel as if you are sleeping well.

So how do you get those golden 90 minutes? Mr. Nishino explains that the point is “body temperature”. “The core body temperature is high during the day and low when sleeping. It is important to control the rise and fall of

Also, preparation for sleep “starts in the morning”. “Good sleep depends on good awakening. What you do when you wake up in the morning and how you spend your daytime are also important conditions for improving the quality of sleep.” We asked Mr. Nishino to give us 8 ways to get the best sleep possible. Let’s try it now.

Remember! 8 Ways to Eliminate Sleep Debt

8 Ways to Eliminate Sleep Debt

Sleep Debt Elimination Method 1: Take a bath 90 minutes before bedtime

Mr. Nishino recommends taking a bath to get a good night’s sleep. “It depends on the conditions, but when you take a bath, your core body temperature rises by about 0.5°C. Since your core body temperature tries to drop by the amount that has risen, a sudden drop occurs after you take a bath. They are connected.” (Mr. Nishino). In other words, the trick is to “raise and lower” the core body temperature. It takes about 90 minutes for your core body temperature to return to normal, so it’s best to finish your bath 90 minutes before bedtime.

Sleep debt relief method 2: Alarm with two time settings

Nishino-style alarm utilization technique is “two time settings”. The first alarm is very faint and set short. The second time, set it to normal sound and after 20 minutes. “In the early morning, there is a lot of light REM sleep, so it should be easy to wake up even with a small sound, and you should be able to wake up well. If you are in deep non-REM sleep, the second alarm will wake you up.”

Sleep debt relief method 3: Take off your socks when you go to bed

Are you wearing socks to sleep because your feet are cold? Actually this has the opposite effect. “When your hands and feet warm up, you naturally feel sleepy. Since heat dissipation is hindered, it is difficult for the core body temperature to drop, and it becomes difficult to fall asleep,” says Nishino. Wear socks until just before going to bed. Take it off when you go to bed. When it is really cold, it is effective to improve blood circulation with a footbath.

Sleep Debt Elimination Method 4: Do not bring your smartphone to bed!

Do not bring your smartphone to bed

Be careful of your smartphone or computer before going to bed. “We know that when the retina detects the blue light emitted from the screen, the level of alertness increases. Also, operating a smartphone excites the brain,” says Nishino. It is a good idea not to bring your smartphone to bed.

Sleep Debt Relief Method 5: Wake Up in the Sun in the Morning

The human body clock is slightly longer than a day, about 24.2 hours. “Sunlight is what corrects this gap. When you wake up in the morning, expose yourself to the sun and switch to wakefulness,” says Nishino. In addition, if you have cataracts, your sensitivity to light may be dulled, which may affect sleep and body rhythms.

Sleep debt relief method 6: Take a nap for about 20 minutes during the day

If you feel sleepy during the day, take a nap. However, do not take a long nap in the evening as it will affect your sleep at night. Mr. Nishino says, “It’s good to take a nap for about 20 minutes” until 3:00 pm. It has also been reported that those who take a nap of less than 30 minutes have about one-sixth the risk of developing dementia compared to those who do not have a nap habit.

Sleep Debt Relief Method 7: Raise Arousal with Bare Feet

Raise your alertness with bare feet

When you wake up in the morning, don’t wear slippers and stand up barefoot. This is a technique that effectively raises alertness. “There is a part called the ascending reticular formation in the brainstem deep in the brain, and it is known that stimulating this part will wake you up. The reticular formation is also activated, turning on the awakening switch,” says Nishino. Washing your hands and face with cool water also cools your skin and wakes your brain up.

Sleep debt relief method 8: Throw away the belief that you can’t sleep

“Some people overestimate their difficulty falling asleep or waking up in the middle of the night and complain that they can’t sleep. It’s normal to take 20 minutes to fall asleep and wake up 3-4 times during the night. No worries!

Snoring, drowsiness… beware of diseases that lead to sleep debt!

Beware of Diseases That Lead to Sleep Debt

I can’t sleep well, I have trouble waking up in the morning, and I’m attacked by strong sleepiness during the day… There may be a hidden illness in the background of such troubles.

“Sleep apnea syndrome is a typical example. It is often associated with obese middle-aged men, but women and thin people are not unaffected. In the case of elderly people, it can be complicated by diseases such as heart failure. It can also develop after a period of time,” says Nishino.

There are also reports that the incidence increases after menopause in women. If your family points out that your snoring is severe or that your breathing has stopped halfway through, get an examination at a specialized medical institution as soon as possible.

Interview/Text: Setsuko Sada

Held on December 9, 2022! <Online> Akiko Yamashita’s “Rejuvenating Sleep” Lecture

A “rejuvenating sleep” lecture was held by Dr. Akiko Yamashita, a neurosurgeon who is familiar with anti-aging and mental health. For good sleep, such as body scan meditation that helps you fall asleep better before going to bed, poses that activate sleep hormones, methods to increase happiness hormones by recording emotions, specific measures to reduce stress hormones, etc. I will teach you simple care that you can do yourself.

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