Neuroscientist Dr. Haru's Concerns About Children's Sleep - Vol. 2 Don't Miss the Signs of a Sleep-Deprived Brain!

A 2014 survey report by the Ministry of Education, Culture, Sports, Science and Technology revealed that one in four junior high school students and one in three high school students feel they don't get enough sleep. A brain that doesn't get enough sleep accumulates "memory garbage" without being able to process it, unconsciously building up stress. Do children who are prone to irritability get enough sleep?

Good Sleepers are Good Learners

Smartphones have become commonplace among children. Even my child, who is less than a year old, is very curious about my smartphone, fiddling with it and even trying to bite it. If children grow up in an environment where smartphones are so accessible from such a young age, it's inevitable that smartphones will become a normal part of their lives. Indeed, a 2017 Cabinet Office survey showed that over 55% of elementary school students and over 65% of junior high school students own or use smartphones or mobile phones.

A study that investigated the relationship between academic performance and sleep habits among American high school students found that students with poor academic performance (grades C, D, F) went to bed 40 minutes later and slept 25 minutes less than students with good academic performance (grades A, B). Similar results have been shown in Japan, not just in America.

It has been proven that lack of sleep can actually reduce learning ability. For example, experiments on adults have shown that chronic sleep deprivation leads to a decline in cognitive task performance, such as memory. While we sleep, our brain transfers memories from the hippocampus, a temporary storage area, to the neocortex. This transfer is insufficient when we don't get enough sleep.

Interestingly, a study of 290 Japanese children aged 5-18 found that children who got enough sleep had larger hippocampi compared to those who slept less. Since the hippocampus is involved in information storage and processing, its size may be related to children's learning ability.

If you want your child to get better test scores, instead of saying, "Study!", why not tell them, "Get a good night's sleep tonight!"?

Sleep-Deprived Brains Creating Irritable Children!?

"My child doesn't sleep much, so they're always in a bad mood," is a common complaint. This might actually be true.

A 2014 survey by the Ministry of Education, Culture, Sports, Science and Technology showed that the proportion of children who responded "I get irritated for no reason" increased as their bedtime became later. A survey of junior high school students also showed that the later their bedtime, the higher their level of irritation and the worse their depressive and anxiety symptoms became.

Why does a disrupted sleep routine lead to emotional instability? There was an experiment where healthy adults were divided into two groups: one group stayed awake all night, and the other slept normally. Afterward, they were shown 100 photos, and their brain responses were observed. The 100 photos included a variety of images, from emotionally neutral to those that evoked negative emotions. The results showed a difference in the amygdala, the part of the brain that processes feelings of fear and dislike. In the sleep-deprived group, the amygdala's response to negative photos was 60% higher, while in the well-rested group, the response was suppressed. Further investigation revealed that a good night's sleep strengthened the connection between the prefrontal cortex and the amygdala. The prefrontal cortex is responsible for reason and controls the function of the amygdala, and thus emotions, through its connection to the amygdala. When sleep-deprived, this emotional control "brake" weakens, making it easier for emotions to become unstable.

So, to what extent can parental discipline change a child's sleep habits? A large-scale study of 15,000 American middle and high school students found that if parents set a bedtime of midnight or later, compared to setting a bedtime before 10 PM, the child's actual bedtime was delayed by an hour, sleep duration was 40 minutes shorter, and the risk of developing depressive symptoms increased.

To maintain a child's mental health, it's important to discipline them not to stay up late.

Haru-sensei's profile:
Haruhisa Okawa
Graduated from the University of Tokyo. Received Ph.D. in Neuroscience from the University of Southern California.
Subsequently, worked as a neuroscientist at Washington University for approximately seven years.
Afterward, served as a project manager for neurological projects at a foreign pharmaceutical consulting firm.
Currently works at a foreign pharmaceutical company in the central nervous system department. 

References:

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• Cabinet Office 2017 Survey Report on the Actual State of Internet Use Environment for Youth https://www8.cao.go.jp/youth/youth-harm/chousa/h29/jittai_html/2_1_1.html
• Japan School Health Association 2016-2017 Survey Report on the Health Status of School Children and Studentshttps://www.gakkohoken.jp/books/archives/208
• Tokyo Metropolitan Government Survey on the Use of Mobile Phones and Smartphones by Youth in Householdshttps://www.metro.tokyo.lg.jp/tosei/hodohappyo/press/2019/05/09/16.html
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• Children with Sleep Disorders Masako Okawa