How Light effects Melatonin and Sleep

cartoon image depicting restful sleepYou heard me mention color temperature before, and the effect of watching TV or reading on the iPad before bed  (See Sleepy Yet? — How Light from Electronics Effects Sleep), but here’s why it’s important.

This WebMD article examines the hormone melatonin, which helps regulate sleep & wake cycles (the circadian clock). Melatonin production in the body is triggered by darkness and inhibited by light, and that explains why we have trouble with jet lag, shift work, and winter months with fewer daylight hours.

This Wikipedia article describes light therapy and melatonin supplements as treatment for sleep disorders like insomnia. It also describes the light color temperature, from the warm yellow of incandescent light bulbs, to blue light of the new fluorescent and LED bulbs, or the bluish tint of the iPad and TV screens.

One way to fool the body into producing melatonin earlier so you can go to sleep earlier is to select warm-color light bulbs and have them dimmed in the evening. Another way is to wear DARK AMBER or ORANGE sunglasses in the evening to block blue light (short light wavelengths). And of course, that’s why sleep experts advise against using a computer or watching TV shortly before bed.

Because my wife and I often watch TV immediately before bed, and she likes to look at videos of our granddaughter on her iPad then, I checked the iPad Settings and found a way to dim the backlighting intensity and set it to somewhat adjust automatically depending on the ambient light. Go to Settings / Brightness & Wallpaper.

I’d also like the iPad to change the color temperature at night but found nothing native in the iPad, so I searched for a reliable iPad app for that. I found iJetlag and TheSleepApp but was disappointed with both of them. One even used the wrong color of light to encourage melatonin production and encourage sleep.

Additional sources of sleep information include the two articles on this site by PhD sleep consultant Bruce Meleski (Sleep Balance – Your Path to Better Sleep and Brain Entrainment for Better Sleep and Health) and in Jeanie Wolfson’s article on Sleep: Timing of Melatonin, Light, Dark, & Use of Other Aids. Wolfson lists many suggestions for improving sleep, including these few:

  • Keep bedroom dark or wear an eye mask.
  • Keep room cool and feet warm.
  • Find a mattress that works for you, trying harder, softer, coil, foam, gel, waterbed, or hammock.
  • Block distracting sounds with white noise.
  • Use lighting controls to simulate dawn before alarm sounds.
  • Don’t watch TV, use a computer use, or do homework within an hour of going to bed.
  • Avoid caffeine and snacks that can cause a blood-sugar drop during the night.
  • Establish a strict sleep/wake schedule.
  • Exercise regularly.



9 thoughts on “How Light effects Melatonin and Sleep

  1. Light therapy works for 90% of users and this one time investment intrigues more and more people. Light therapy seems to be a universal solution and you can now own acne lights for home use.

  2. Here’s a great resource about the affects of Light on Sleep Quality and General Health:
    Light & Health Research Foundation (SOLG) —

    CLICK the British flag at top/right for an English version.

    Also, I posted a link to my Economic Value of Good Sleep article in a Linkedin group on Light Therapy, and it has started a discussion of sleep benefits among sleep experts worldwide.

    Douglas Steel pointed me to the website for the National Sleep Foundation ( and several statistics there, but I found them less than credible and responded:

    I found the statistics you cited but can’t believe them. $18 billion/year in lost US worker productivity is just $116/year per worker. That’s only 2.6 hours per year or 3.2 minutes per day, based on US Census data of 154 million employed individuals earning an average of $88,000 per year.

    I can’t claim that my model is gospel either, but I do think it’s a more reasonable start at estimating the costs, and I hope others can poke holes in my assumptions or provide other credible data.

    What I tried to do with my model was to put the value of good sleep into terms that everyday consumers can relate to and that might influence their behavior. I’d like to find a similar approach to quantify sleep value for other stakeholders, including employers, policy makers, health care providers, insurance companies, and product manufacturers. The $18 billion per year Sleep Foundation estimate is not credible enough, in my opinion, to post on my website to support the Good Sleep message.

    Total employer benefits must include the trickle-down effects, including increased productivity that leads to better competitiveness and market share. Total social benefits must include the impact on lives saved from fewer accidents, the healthcare system from less chronic illness, auto & health insurance premiums, increased GDP and tax revenue, and the impact on global competition.

  3. Dear Mhealthtalk,
    This might be off topic, however, Dear Mhealthtalk,
    I was wondering on a similar note,, The patio or the backyard is a place where the family can entertain guests, hold parties or just hang out with each other.  It can be a place for dining, cooking barbeque, playing cards or maybe even swim in a pool.  All of these activities usually take part during nighttime that is why the right kind of patio lights should be chosen to provide the right amount of lighting in the patio.
    Great Job!

  4. Incandescent bulbs are so called because of the heat produced. Incandescence means to glow with heat. The tungsten filament is found inside a void within the bulb. When energy is pumped through the wire, the electrons react and there is resistance. Then, the filament will get so hot it will glow.

    (Editor: The light from a hot filament is somewhat like the light from a campfire, i.e. warm coloration, as opposed to the blueish or greenish light of fluorescent lights. I also removed a potentially dangerous link.)

  5. I really enjoyed this article as I am trying to find out as much information as possible so that I can be assured that I am getting the best rest possible. One last thing that I didn’t see mentioned is just to try to get as much natural sun light as possible or going to a tanning salon during the day for what you deem and appropriate amount of time. Both have helped me the past and others that I know. 

    1. Thanks for your reply, Thomas. Getting enough natural sunlight during the day can certainly help program your biological clock and circadian rhythms. Also helpful is high-intensity and full spectrum lights or just positioning your desk by a window, but I don’t recommend tanning beds even in winter due to the cancer risks. 

    1. Thanks, Jeff, for your response. The SleepShield filters seem like a good idea, at least until Apple modifies iOS to support a software solution like flux (See comment at

      I smell “snake oil” in the Good Night LED Sleep Lights, however, because of the wild claims, my understanding of the physics, and the lack of evidence substantiating their claims. Sorry, but an endorsement by Dr. Oz is not enough since he lacks credentials in this space. Here’s some info from the CES trip report I’m finishing:

      I’ve long been a fan of the Philips Hue light bulbs, which you can buy at the Apple store, because you can turn them on & off, control intensity, and even control COLOR TEMPERATURE through the iPhone. What makes that a great feature is how artificial light affects melatonin and sleep. But the Philips bulbs are expensive and require a Zigbee wireless network hub, so I was happy to see new competitors

      Belkin’s WeMo Smart LED Bulbs and home automation kit uses your Wi-Fi home network and allows you to control, schedule and dim your lights from anywhere. The 60-watt bulbs are brighter and last longer than the Philips Hue but have a fixed 3000-Kelvin warm white color (arguably less blue light). Fully dimmable, WeMo Smart LED Bulbs can be controlled individually or in groups. The Starter Set includes two LED Smart Bulbs and a WeMo Link, which can support up to 50 individual Smart bulbs.
      Individual WeMo Smart LED bulbs will be sold separately. 

      YiFang Digital introduced a Bluetooth-connected smart lighting system that gives users similar control over their home lighting through a free app for iOS or Android devices. It allows them to turn the lights on or off; control brightness, color & preset scenes (e.g. Romantic, Movie, Dinner, Relax, Sleep); and program lights to change automatically throughout the day. The system supports 4S/5 and Samsung Galaxy S4 smartphones, and as with most other Bluetooth devices, it has a working distance of about 30 feet.

      The BeeWi LED light bulb also has many of the same features at the Philips Hue, including adjustable colors, but it’s much cheaper (less than $40 per bulb), brighter (60W equivalent), and uses Bluetooth instead of Zigbee (no need for a separate hub). One problem with the Bluetooth connection is that you can’t control the lights remotely, but an optional “Smart Gateway” solves that and bridges between your Wi-Fi home network and Bluetooth, thus giving BeeWi users the best of both worlds.

      The Withings Aura (0:54 video) has a sensor pad that goes under your mattress to monitor your sleep and help wake you up gently. It plugs into a bedside alarm clock, speaker, and LED table lamp, where colors and sounds simulate dawn and dusk. With selected light colors, it can inhibit or trigger the body’s production of the hormone melatonin and either wake you or help you relax and fall asleep.

      Withings says the mattress pad picks up “micromovements” that are far more sensitive than most wristbands and activity trackers. The sensor can even detect tiny movements from under a pillow-top or tempurpedic mattress, which is designed to minimize movement. Separate sensors can monitor sleep
      patterns for two people in the same bed, and it detects not just movements but also breathing and heart rate. This allows Wighings to make much more sophisticated conclusions about that nature and quality of your sleep. With this data, the Aura alarm unit can wake you when it makes sense, rather than abruptly at a specific time.

      The $299 starter kit includes one sensor pad and one nightstand alarm/light. >

  6. You can invertthe the colors on an iPad which makes white backgrounds black. It’s great for reading (I use it every night) but not so good for videos or images (like looking at film negatives). Hit he home button 3 times in a row and it’ll bring up a menu.

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