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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