Dr. Haru, Neuroscientist: Troubling Children's Sleep – Vol. 1: Save the Sleepless Zombies!

Everyday is busy. When do you feel most relaxed after returning home? For me, it's when I see my children's faces. I love them so much, but I'm also sleep-deprived every day (sweat). Many of you might think that children are lucky to sleep as much as they want, whenever they want, but are you aware of sleep deprivation in children?

Blue light disrupts the body clock!

Smartphones are now commonplace even among children. Even my child, not yet one year old, is fascinated by my smartphone, playing with it and gnawing on it. If they 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. In fact, according to a 2017 Cabinet Office survey, the ownership and usage rate of smartphones and mobile phones among elementary school students exceeded 55%, and among junior high school students, it exceeded 65%.

So, how has the spread of smartphones affected children's sleep? According to a 2012 survey by the Japan School Health Association, the average bedtime for children becomes later as they get older: 10 PM for 5th and 6th graders, after 11 PM for junior high school students, and 11:45 PM for high school students. On the other hand, various surveys indicate that using smartphones late at night leads to sleep deprivation. In a 2019 survey conducted by the Tokyo Metropolitan Government targeting 2,000 guardians of elementary, junior high, and high school students who own mobile phones, about half responded that owning mobile phones had some impact on sleep, eyesight, parent-child communication, or academic performance. Surprisingly, "using mobile phones/smartphones late at night resulting in sleep deprivation" was the most common answer at 20%.

In reality, sleep deprivation caused by smartphone use is not solely due to going to bed later. The light emitted from smartphones shifts our body clock to a nocturnal rhythm. Our body clock is controlled by a region in the brain called the suprachiasmatic nucleus. The suprachiasmatic nucleus, in turn, acts on a part of the brain called the pineal gland, controlling the amount of melatonin secreted by it. Melatonin promotes sleep; its secretion increases at night, making us sleepy, and decreases in the morning, waking us up. The backlights of smartphone screens contain a lot of blue light, and the system that controls the body clock is particularly sensitive to this blue light. For example, one study reported that using an iPad for two hours before bed reduced melatonin secretion by 23%. Even in strictly controlled laboratory experiments, when participants read on an iPad for several hours before bed for one week, their melatonin secretion decreased by more than 20% compared to reading a physical book, and the onset of secretion was delayed by up to three hours.

Modern children, by using smartphones late at night, may not only be sleeping less but also having their body clocks disrupted, leading to a later actual sleep onset time. The best solution is not to use smartphones at night, but cutting blue light can also be considered a measure. Recently, it has become possible to apply blue light filters on devices, either through OS features that reduce blue light or dedicated apps. Why not try this as a first step to gradually help children return to their normal body clock?

Were Children Originally Night Owls?!

Oh no, I overslept! I have to hurry and get ready for school!

This is common for children who aren't morning people. Especially during adolescence, parents might find themselves raising their voices at children who struggle to wake up, thinking they are just being lazy. However, this is not 100% laziness; it can be considered a physiological phenomenon due to children's body clocks differing from adults'.

During adolescence, the biological clock controlled by the suprachiasmatic nucleus in the brain advances, and the timing of melatonin secretion, which promotes sleep, is delayed. Consequently, while children around 10 years old tend to be morning types, they shift to a night-owl type during adolescence and early adulthood, becoming most nocturnal around age 20. There is even overseas data suggesting that 20-year-old males shift to being nocturnal by approximately two hours compared to 10-year-old males. This means that during adolescence and early adulthood, due to hormones, it's easier to stay up late and oversleep. Even if they go to bed late, school start times don't get later. For children going to school, waking up at 7 AM might be as tough as waking up at 5 AM is for their parents.

Choose bedding that fits your body and helps you relax

Considering that children's body clocks naturally delay, early school start times might not be suitable. In fact, overseas, many benefits have been observed when school start times are delayed, such as increased attendance rates, reduced behavioral and mental problems in children, decreased alcohol and drug abuse, and even fewer car accidents and lower mortality rates. It's not just about reducing problems. For example, a school in Minnesota reported improved student grades when its start time was shifted from 7:25 AM to 8:30 AM. Similar results have been obtained in schools across various states in the US.

While there may still be room for societal discussion on school start times, delaying them is currently a difficult issue. As parents, what we can do is be mindful of children unnecessarily staying up late and accept that oversleeping in the morning is a natural biological change.

Haru-sensei's Profile:
Haruhisa Okawa
Graduated from the University of Tokyo. Graduated from the University of Southern California, Ph.D. in Neuroscience.
Subsequently, engaged in research as a neuroscientist at Washington University for approximately 7 years.
Later, responsible for neurological projects at a foreign pharmaceutical consulting firm.
Currently employed at a foreign pharmaceutical company, belonging to the central nervous system division.

References:

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• Cabinet Office, 2017 Survey Report on the Actual State of Internet Use Environment for Youthhttps://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 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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