I've outlined the harmful effects of blue light at night (from TV, computers, phones, tablets, and CFL/LED bulbs) on adults. Quick overview: it increases the risk of depression, anxiety, weight gain, diabetes, and certain cancers.
What does light at night do to kids?
There have been several studies over the past few years that paint an alarming picture of what blue light is doing to your kiddos.
A 2014 study in the Journal of Clinical Endocrinology and Metabolism measured the amount that melatonin was suppressed by moderately bright indoor light at night. For adults, melatonin was suppressed by 46% on average, but for kids, melatonin was suppressed by 88%!
Another study of preschool-aged children published in 2018 found a similar result (88% melatonin suppression due to bright light). But this study went one step further and continued measuring melatonin levels for almost an hour after the preschooler's normal bedtime. The children were exposed to the bright light for an hour before their usual bedtime, and then stayed awake, but in dim light for the next hour. Melatonin levels stayed suppressed for that next hour, and for 70% of the kids, it was suppressed for the hour by more than 50%.
Part of the reason for children having a greater susceptibility to light is due to the fact that their eyes are simply more sensitive to light. As you age, the lens of the eye becomes more crystalline and allows less light absorption. A 2008 study showed that by the time you are 45, you have "only half the circadian photo reception of early youth."
Studies that focus on sleep illuminate (pun intended) part of the problem:
Recently, studies have shown that 50-90% of US school-aged kids don't get as much sleep as they need. It is recommended that kids age 6 - 13 get between 9 and 11 hours of sleep each night, with teenagers needing between 8 and 10 hours per night. While busy schedules and homework play a part in keeping kids up later, it is clear that light at night, especially from electronics, is impacting children's sleep and overall health.
A 2014 study from the National Sleep Foundation showed that 72% of kids aged 6 - 17 usually have at least one electronic device (TV, smartphone, tablet, laptop, video game player) in their bedroom at night, with 34% of parents acknowledging that their child leaves at least one electronic device on while sleeping.
Sleep disturbances often go along with ADHD. But some researchers are pointing to sleep disruption actually causing ADHD symptoms. One study found that, even adjusting for TV viewing or outdoor activities, a delayed bedtime was associated with a 2.5X increase in ADHD. The study also found that frequent sleep problems were associated with a 4X increased risk of ADHD.
Other studies have similar findings relating both difficulty falling asleep, bedtime resistance, and shorter sleep duration to an increased risk for ADHD.
This doesn't necessarily prove that light at night causes ADHD for everyone, since ADHD seems to be a multifactorial condition. But why not try blocking blue light at night to see if ADHD symptoms improve?
What about teenagers?
A 2015 study looked at both pre-pubertal and post-pubertal adolescents. The study participants wore eye shades for 10 nights before the in-lab study began. Then the participants were exposed to different lighting conditions over four nights. The results showed that bright light (500 lux) at night, of course, suppressed melatonin quite significantly in both the pre- and post-pubertal adolescents. Overall, the effect of light was more significant on pre-pubertal study participants, and for dim light, (15 lux) the effect on melatonin suppression was only seen in pre-pubertal participants.
Another study looked at the increase in inflammation due to shorter sleep duration in both older and younger teenagers. The study found that younger adolescents had an increase in CRP, a key marker of inflammation, when they had a shorter average sleep duration. The researchers also found that for both younger and older teens inflammation increased due to variability in the sleep duration over the course of a week. Staying up late a couple of nights and then catching up on sleep on the weekends gives a big variability to sleep duration, and this increased CRP levels.
What can you do?
For younger kids, have a shut-off time for all electronic devices that is at least an hour and a half before bed. Yes, it may be a bit bumpy to make the change initially, but plan it out to have bath time, story time, and time for getting things ready for the next day.
To eliminate blue wavelengths coming from your main overhead room lighting, get some lower watt antique style bulbs that are yellowish in color. Amazon has lots of options (photos below), or if you live near a Lowe's, they carry GE bulbs that are labeled as 'candle' glow. Put these into lamps in the rooms that your kids are going to be in before bed – their bedroom, bathroom, living room, etc. And then turn on the lamps and turn off the bright overhead lights. This will create a nice warm lighting environment that is still bright enough to see well, but no longer as bright as it is with the overhead (blue-wavelength containing) lights.
For teenagers, well... anyone who has had teenagers knows how hard it can be to enforce a rule like "no electronics after 8 pm". (Cue the laughter and eye-rolling :-) One option is to turn off the wifi in your home at a certain time of night. You can automate this with a wifi-enabled outlet.
A better option may be to have your teens read through several of the studies that show that light at night is a problem. Let them see the impacts and make the decisions. Then challenge them to a one week trial of eliminating blue light for two hours before bedtime. (Do it along with them.) Pick a week when you don't have many social engagements at night.
Blue-blocking glasses are an excellent option for teens. Let them pick out the style - there are lots to choose from on Amazon. Why do a one week challenge? Studies show that the body's melatonin production will rise by 50% after using blue blocking glasses for one week.
Just like above, also get some lamps for your teenagers' rooms and put in the 'Edison' bulbs or bulbs that are labeled as candle glow. Your goal is a dimmer overall lighting with a shift towards the red end of the light spectrum. If your teens are girls and into crafts, have them find ways to use fairy lights - perhaps by putting them in orange colored glass vases or in Mason jars painted red, orange, or copper.
How much is a 'lux'?
If all the talk above about dim light, bright light, and lux aren't clear, here is a graphic that I made to show nighttime light sources:
Words of encouragement...
Let me end by saying that I hope you come away from this article with two things: one, a realization that blue light at night matters to our kids' health, and two, that there are many inexpensive ways we can mitigate those effects.
Please spread the word! Tell other parents, tweet this or put it on Facebook. We can change the next generation through just a simple, foundational step.