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Lights emitted by smartphones eroding your sleep


Japan, says Shukan Asahi (Aug 17-24), is “an insomnia superpower.” That’s an unenviable distinction, as anyone who suffers sleep deprivation knows – and some 80% of Japanese do, experts say.

That’s not to say 80% of Japanese are full-blown insomniacs. Only 20% would qualify as that – a high proportion all the same. But 80% don’t sleep long or deeply enough, to the point that it adversely affects their daily lives. And it’s getting worse – owing, researchers are increasingly inclined to think, to increased use of smartphones. The blue light that smartphone screens emit just isn’t good for us, it seems.

The scientific explanation, courtesy of Kyorin University psychologist Yoshihiko Koga, is this: Blue light waves measure in at 380-495 nanometers (a nanometer is one billionth of a meter). That’s as short as visible light waves get. The shorter the wave, the higher the energy. Invisible ultra-violet light waves, shorter and more energetic, are known to age cells and cause eye damage.

The effects of blue light have yet to be pinned down with certainty, but the following test gives a clue: Participants used smartphones intensively an hour before bedtime, half of them wearing special spectacles that filter out half the blue light, the other half not. Then the sleep of all participants was assessed for quality and length. Those who had worn the spectacles slept on average 30 minutes longer than those who had not, and more of them said they woke up feeling refreshed physically and mentally.

Experts quoted by Shukan Asahi say evidence is growing that blue light damages eyesight over time. Especially vulnerable in this regard are children, whose eye lenses are more transparent than those of adults. “Children nowadays are exposed to LED liquid crystal screens from the time they’re very small,” says ophthalmologist Takeshi Iide. “There are concerns regarding the future effects on their eyes.”

To anyone old enough to remember a different time, it is astonishing to consider that between smartphones and personal computers, between work and personal use, an average company employee spends no less than 11 hours a day peering at a screen. Even if the scientific evidence linking this to increasing sleep disorders has not yet attained the level of certainty, it is at least, says Shukan Asahi, suggestive.

The magazine concludes with a checklist of 10 rules for sounder sleep, most of which we’ve heard before. Get up every day at a fixed time, have dinner three hours before bedtime, bath two hours before, shut down the computer and smartphone three hours before, learn to be satisfied with one beer with dinner, and so on in that vein.

It all makes perfect sense, except that such a calm and orderly withdrawal from the affairs of the world at the end of the day may not be possible in these feverish times of ours.

© Japan Today

©2024 GPlusMedia Inc.

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I definitely sleep better since I stopped taking my iPad to bed... :-)

4 ( +5 / -1 )

So in this researcher's opinion the 30 minutes of sleep people miss out on because they play with their smartphone is more important than the 2 HOURS of sleep the Japanese regularly skip because of their school and work commitments?

.... this research is seriously misguided. Would it be better if people didn't use their smartphone before bedtime? Yeah, sure. Is blue light dangerous... don't be idiotic, it's the same as summer light and may actually be helpful in reducing symptoms of depression (something this article neglected to mention).

... but the REAL problem is that the Japanese don't follow the basic rules for sleeping or get enough. The smartphone thing is tiny part of a MUCH bigger problem.

3 ( +6 / -3 )

There's an app called F.lux which is available on PC, iOS and Android (coming soon) which solves this problem. Check it out:


0 ( +2 / -2 )

The blue light? What are they talking about?

2 ( +2 / -0 )

Do you also have to shut down your TV three hours before sleep?

3 ( +3 / -0 )

Thomas, you beat me to it! I too have Flux and love it. You can even set it for a time zone other than your own, so that if you work odd hours, like I do, you can have the computer in "sunset mode" colors just before heading off to slep.

I started using Flux and while it takes time to get used to seeing what looks like a yellow-orange tint to your screen, it really is relaxing. Much less eyestrain before sleeping -- highly recommended!

(And no, I'm not one of the developers. Just a satisfied user.)

Frungy's point is a good one: smartphones are just one small part of the problem. Japanese society relentlesly deprives people of sleep, and it starts with high school when studying for entrance exams (kids stay up late at their desks; somehow the possiblity of getting an advantage from having a well-rested brain is never considered), and continues into the working world (where a salaryman is lucky to have 8 hours free in his own home per day, much less 8 hours of sleep). Laying off the computer and phone before bed will help, but being able to get to bed more than 8 hours before you have to wake up again will do a lot more.

1 ( +1 / -0 )

Thanks so much for that link Thomas! I'm using it on my laptop (I would have to jailbreak my iphone), but my eyes feel really better after just a couple of minutes using it! You can feel the strain drop away. Please send the link to Shukan Asahi!

0 ( +0 / -0 )

Llearn to be satisfied with one beer with dinner,

Ain't gonna happen.

-1 ( +2 / -3 )

A great chance for an inventor to make lots of money with a "blue light" filter for your smartphone, TV and whatever.

0 ( +0 / -0 )

Blue light is dangerous for your eyes/ creates anxiety/ energy so you can't lsleep VS. Blue light is the same as summer light and not at all dangerous and cures depression??


I agree w/ one or two somebodies above, article could be better written. Japan is sleep-deprived because of smart phones? Or sleep deprived and smart phones making it worse? They start with one, wander off into the other topic, and never resolve the first.

I have no smart phone and cannot sleep the last two years. I will keep my reasons a secret! But it is a high-pressure society here.

-1 ( +0 / -1 )

Don't have any electronic items in the bedroom, other than a battery powered alarm clock. No smartphone, mobile phone, iPod , iPad, computer, or anything with a screen and noise. Telephone is in the room next door, and all the electronic 'stuff' stays downstairs...always get a good night's sleep :-)

-1 ( +0 / -1 )

Right now I am dictating from my iPhone. It is 3:22 am in Brazil ;( Argh!!!

0 ( +0 / -0 )

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