Blue light and sleep

The information in this post comes from a newsletter sent by friend of mine, Enid Fox, who is a fitness and nutrition guru. She is a careful researcher and I trust her information.

Our sleep/wake cycles are regulated by the hormone, melatonin, which is produced by the pea-sized pineal gland located in the brain. The melatonin it produces circulates in the blood. Production of melatonin is triggered by darkness, and its level in the blood usually peaks in the middle of the night. The highest levels of melatonin are between midnight and 8:00. One reason teenagers have trouble getting up is that, for this age group, the nightly schedule of melatonin release is delayed, a situation that leads to later sleeping and waking times.

The thing is, melatonin not only regulates our sleep, it is also a powerful anti-oxidant and anti-inflammatory chemical. One study has shown that people who work the graveyard shift have an increased rate of cancer. So you want to keep your levels of melatonin up. Unfortunately, melatonin production decreases as we age—like so much else, dang it.

What’s important for melatonin production is not sleep itself but darkness. The pineal gland responds to signals transmitted by our optic nerves. When it gets dark, a cascade of nerve signals from the eye to the pineal gland triggers the release of melatonin. But if we bombard our eyes with bright light at night we inhibit the usual surge of melatonin at night, thus lowering the overall production of melatonin.

Dim light has little effect on melatonin, but bright lights, especially the blue lights emitted from electronics can stop the pineal gland from releasing melatonin. One study looked at how melatonin levels were affected by looking at an iPad at night. Researchers found that one hour of exposure to the light didn’t significantly curtail melatonin release, but two hours did. Here’s something else to think about: red-lighted alarm clocks don’t disturb melatonin production very much. But clocks with bright light should never be placed at your bedside.

For a while now I have started reading books on my iPad. Now I’m thinking I need to get out my ancient Kindle, which is not back-lit.

Next week: skin cancer whack-a-mole

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