Log in
Recently, there has been an abundance of information regarding the importance of sleep in online articles and on television, leading many to want to understand the effects of sleep deprivation on the body.
This article is for those who "sleep less than others but don't feel any particular physical discomfort," and it explains the risks of sleep deprivation, its relationship with illnesses, and its impact on both mind and body.
What is Sleep Deprivation?
While the amount of sleep needed varies from person to person, sleep deprivation refers to a state where one doesn't get enough sleep, leading to symptoms like drowsiness, headaches, and fatigue during the day. It is also commonly called "netsubusoku" in Japanese. Sleep researchers sometimes refer to a state of insufficient sleep as "sleep debt." Chronic sleep deficiency can lead to sleep debt, which significantly impacts both the brain and body.
According to the Ministry of Internal Affairs and Communications' "2011 Survey on Time Use and Leisure Activities," the average sleep duration for all ages in Japan is 7 hours and 49 minutes for men and 7 hours and 36 minutes for women. Furthermore, for the working and child-rearing generations aged 35-39, this shortens to 7 hours and 24 minutes for men and 7 hours and 22 minutes for women. The shortest sleep duration for both men and women is found in the 45-49 age group, with men averaging 7 hours and 18 minutes and women 6 hours and 48 minutes.
Reference: 2011 Survey on Time Use and Leisure Activities | Ministry of Internal Affairs and Communications
Sleep Deprivation Checklist
In addition to insufficient sleep duration, sleep deprivation can also occur due to poor sleep quality, even if you sleep for a long time. If you check even one of the following items and it interferes with your daily life, you should consult a medical institution as soon as possible.
- It takes 30 minutes to an hour or more to fall asleep after getting into bed.
- You wake up multiple times during the night.
- You wake up earlier than your scheduled wake-up time and cannot fall back asleep.
- Your sleep is shallow, and you don't feel rested even after getting enough sleep.
- You experience irresistible drowsiness during the day that interferes with your activities.
- You cannot feel good during the day.
Disadvantages of Sleep Deprivation
Here are four disadvantages of sleep deprivation.
1: Decreased daytime performance
The Ministry of Health, Labour and Welfare's "Deep Relationship between Sleep and Lifestyle Diseases" states that "chronic sleep deprivation not only leads to daytime drowsiness, decreased motivation, and impaired memory, but it is also known to significantly affect hormone secretion and autonomic nervous function within the body."
It is said that "two weeks of 6 hours of sleep per night can lead to the same brain performance as an all-nighter," indicating a close relationship between sleep deprivation and daytime performance.
When your sleep rhythm is disrupted, the sleep hormone melatonin decreases. This decrease in melatonin leads to a vicious cycle of difficulty falling asleep and shallow sleep. As sleep quality declines, body temperature regulation and hormone secretion become imbalanced, making it even harder for the body to recover from fatigue.
Furthermore, stress, which should decrease with sleep, accumulates when sleep-deprived. Continuous sleep deprivation can therefore increase stress and potentially lead to sleep disorders.
2: Prone to Weight Gain
The Ministry of Health, Labour and Welfare's "Deep Relationship between Sleep and Lifestyle Diseases" states, "It has been found that even in healthy individuals, two consecutive days of sleep deprivation (4 hours of sleep) led to a decrease in leptin secretion, a hormone that suppresses appetite, and conversely, an increase in ghrelin secretion, a hormone that enhances appetite, resulting in increased hunger compared to a day of ample 10-hour sleep."
Reference: Deep Relationship between Sleep and Lifestyle Diseases | Ministry of Health, Labour and Welfare
3: Increased Blood Pressure
Sleep deprivation activates the sympathetic nervous system, leading to the secretion of hormones like adrenaline, which raise blood pressure.
Furthermore, if sleep deprivation continues, blood pressure may remain high even at night due to hormonal effects. Persistent high blood pressure increases the risk of cardiovascular diseases, so caution is necessary.
4: Weakened Immunity
In addition to relieving physical and mental fatigue and maintaining overall body function, sleep also promotes the secretion of immune substances (cytokines) that boost immune function. Therefore, sleep deprivation is thought to affect immunity.
Research on sleep and immunity shows that people who sleep less than 5 hours on average have a 4.5 times higher risk of developing a cold compared to those who sleep 7 hours. The risk of a cold progressing to pneumonia is 1.4 times higher for those who sleep less than 5 hours compared to those who sleep 8 hours.
Research has also been conducted on how sleep duration affects the risk of COVID-19 infection. A study of 2,884 healthcare workers in six European and American countries found that for each additional hour of nighttime sleep, the risk of coronavirus infection was reduced by 12%.
Illnesses Caused by Sleep Deprivation
Sleep deprivation, which also affects immunity, is believed to be a risk factor for various illnesses. Major risks include lifestyle diseases such as diabetes, high blood pressure, and dyslipidemia, as well as depression and dementia.
One study reported that 7-8 hours of sleep per night is associated with a lower risk of obesity, high blood pressure, and dyslipidemia, and that the risk of these diseases increases with shorter sleep durations. Furthermore, compared to people who get 7-8 hours of sleep, those who sleep less than 5 hours have a 2.5 times higher risk of diabetes.
Moreover, according to the Ministry of Health, Labour and Welfare's "Deep Relationship between Sleep and Lifestyle Diseases," "it has been clarified that individuals in a chronically sleep-deprived state are susceptible to lifestyle diseases such as diabetes and coronary artery diseases like myocardial infarction and angina pectoris."
Furthermore, research by the National Center of Neurology and Psychiatry has shown that five consecutive days of sleep deprivation, with only about 4 and a half hours of sleep per day, can increase anxiety and depressive tendencies.
How to Avoid the Risks of Sleep Deprivation
While the appropriate amount of sleep varies from person to person and cannot be generalized, it can be difficult for busy modern people to get enough sleep every day. Therefore, recently, attention has been focused not only on sleep duration but also on sleep quality.
To achieve good quality sleep, it is very important to first measure your sleep quality to understand your current state and then create a sleep environment that allows for proper rest.
1: Measure Your Sleep to Check if You Are Sleeping Deeply
2: Optimize Your Sleep Environment with Bedding
Sleeping on bedding that doesn't suit you can worsen sleep quality, potentially leading to sleep deprivation even if you get enough sleep. Therefore, it's important to optimize your sleep environment with bedding that suits you.
Sleep Deprivation Requires Caution
Sleep deprivation carries various disadvantages and health risks, so it's important to get the highest quality sleep possible within your limited time. To do this, why not check your sleep quality or review if your bedding is right for you?
【References】
※2011 Survey on Time Use and Leisure Activities | Ministry of Internal Affairs and Communications
※Deep Relationship between Sleep and Lifestyle Diseases | Ministry of Health, Labour and Welfare
