Light Impacts Sleep

Now that the nights are longer, it’s time to think about the impact light has on our sleep. And oh, does it have impact! This last month it’s been a pleasure to read two books on light, and human’s historical experience of night – The End of Night by Paul Bogard, and At Day’s Close Night in Times Past by A. Roger Ekirch. Let’s dive into some of the details, and then how you can design light exposure to help your sleep.

The negative effect of light at night
Roger Ekirch talks about the human experience of night over the centuries. Streets until the 1600s had only the light spilling from homes to light them. To be out at night was dangerous, and many towns would close their doors at night and enforce a curfew. For safety, fires and candles would be put out before bed. Their use would be conserved to save money, so some poor people would go to bed soon after dark.

Compare that history to the “sky glow” that many of us are now living in, where we can hardly see the stars at night. In The End of Night author Paul Bogard outlines what is lost when we no longer have dark nights. Not only is human physiology influenced, but migrations of birds and the life-cycle of trees is altered.

Melatonin is a hormone secreted by the pineal gland of the brain. Melatonin is nicknamed “the hormone of darkness,” and helps us feel sleepy at bedtime. Unfortunately melatonin is very sensitive to light, particularly blue light, which suppresses it’s release. And what are 90% of us exposed to during the evening? The blue light of electronics which suppresses melatonin!

The positive effect of light during the dayA recent study compared the sleep of office workers who get natural sunlight to those who work on the interior of the building and don’t. Those who got more light during the work day had better sleep quality, slept longer, and had more physical activity. They also reported a higher quality of life – something we’d all like!

Using light exposure to improve sleep
The basic principle is to get historical light levels during both day and night. In other words, bright full-spectrum light it the morning and during the day, then full darkness at night. How can you do that? Here are some ideas:
– in the morning get some bright outdoor light as soon as possible. Maybe go stand on the porch and look out while having your morning tea.
– continue to get bright light in bursts throughout the day
– in the evening, have lights low, and use the yellow-red spectrum if possible (rather than blue or full-spectrum lights). Avoid electronics for the hour before bed.
– if you are up in the middle of the night, again have low lighting. Particularly troublesome in many homes are the bright bathroom lights, instead put a small night-light in the bathroom to use if need be.
– watch out for your neighbors too by turning off outside lights that aren’t truly needed, and if you need outdoor lights, aim them downward so you are not committing ‘light trespass.’ (Interestingly, Bogard cites studies showing that increased lighting does not decrease crime, that criminals like to work in a well-lit area just like everyone else!)

Be purposeful about making all of these lifestyle changes at the same time. Then notice after a week or two how your sleep has changed!

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Sleep In America Poll – Using Technology

The new Sleep In America Poll came out today, the first day of National Sleep Awareness Week 2011.

This poll was all about our use of technology during the hour before bed, our nightly sleep, and daytime function. Here are some of the highlights:
– 63% say that during the week their sleep needs are not met
– 60% say they have a sleep problem almost every night
– 95% of us use technology during the hour before bed a few nights a week or more
– 20% of 13-29 year olds say they are awoken by a text, phone call or email several nights a week
-22% of 13-18 year olds are clinically sleepy
– About 10% of 13-45 year olds say they drive drowsy 1-2 times a week

Even the light from your TV or laptop is enough to suppress melatonin. During the hour before bed your melatonin should be increasing, allowing you to become sleepy and fall to sleep easily. The time for bright light is in the morning to get energized.

Timing Light Therapy and Melatonin Supplements

It’s been fun to talk with people suffering from Delayed Sleep Phase over the last couple days.  There’s been some questions about shifting sleep phase using light therapy and melatonin supplements.  The timing of these therapies depends on whether you want to delay sleep, ie. make it begin later, or advance sleep, making it occur earlier.  Once you know that, then you use the Phase Response Curve to see when to use these therapies.

A word of warning:  The correct timing is crucial, so it is best to work with a sleep professional if you want to shift your sleep phase.  If you use light or melatonin therapy at the wrong time you can cause problems by shifting your circadian rhythm the wrong direction.

Follow this link to the Phase Response Curve on Wikipedia: http://en.wikipedia.org/wiki/File:PRC-Light%2BMel.png

On the horizontal axis you see time, and the sleep period written in.  On the vertical axis you see hours of phase advance on the top, and hours of phase delay on the bottom.  Bright light is represented by dark purple, melatonin by green.  Note that the light curve goes both higher and lower than the melatonin, that is because a much larger phase shift can be achieved with light.

Let’s look at an example.  Say an adult is unable to sleep until 2am, but must get up for work at 7am.  Getting 5 hours of sleep each night is not enought for her.  She would like to sleep from 11pm to 7am, but is just not sleepy.  Using the Phase Response Curve, she begins using light therapy each morning when she gets up for the day.  She also takes some melatonin 6 hours before bed.   These combined therapies allow her to feel sleepy at 11pm, and fall to sleep easily.  Now she can get a full night’s sleep, and all the benefits of sufficient sleep.

Zeitgeibers

What is a zeitgeiber???

The word ‘zeitgeiber’ comes from the German language, and means ‘time giver.’ Zeitgeibers are clues in the external world that help keep our internal body clock in sync with the 24 hour day/night rhythm. This word is used a lot in the field of chronobiology.

The most meaningful zeitgeiber is light, as it impacts melatonin, which in turn sets our circadian rhythm. Other zeitgeibers include meal times, exercise times, and social activities. When your zeitgeibers happen at close to the same time each day, you will be more firmly in sync with the 24 day/night rhythm. This can pay off in sleeping well, and being fully alert during the day!

Is it Insomnia or Delayed Sleep Phase?

Insomnia is an inability to fall asleep easily or stay asleep throughout the night. Delayed Sleep Phase is when a person is on a later schedule than the norm. The tricky thing is that Delayed Sleep Phase can masquerade as insomnia, because it can also cause difficulty falling asleep.

In Delayed Sleep Phase the circadian rhythm is pushed later, so the person doesn’t get sleepy until later than the norm. So if he tries to go to sleep at a normal time, he lies awake in bed, and experiences insomnia. However, if he goes to bed later when he feels sleepy he will have no sleep problem.

Recently I saw an adult woman who had delayed sleep phase, but who had been diagnosed with insomnia and treated with sleeping pills. One of the clues that she had Delayed Sleep Phase is that she said ” I am never sleepy at bedtime.” We shifted her circadian rhythm earlier, using light therapy and precisely timed melatonin.

Within 6 weeks she was sleeping well through the night, without the sleeping pill she’d previously taken.  Her last comment to me was “Now there’s nothing for me to do but keep on sleeping.”

To learn more about Naturopathic Sleep Medicine and Dr. Catherine Darley please go to www.naturalsleepmedicine.net.  Sleep Well, Naturally.