If you’re reading this blog, chances are you’re already aware of the terrible effect light can have on your sleep. Our manifesto, “Sleep Hygiene 101,” explained the basics. After sundown, the circadian rhythms in a healthy body initiate a hormonal cascade. This leads to glorious, natural, stress-reducing and immunity-enhancing sleep.

But. If you allow any form of unnatural electric light to enter your pretty eyeballs after sundown, your optic nerve sends a signal to you brain: “It’s daytime! Stay sharp!”

If falling sleep, staying asleep, and maintaining robust health are your goals, this is a problem.

It’s even worse if you never experience “sundown” at all. If you stay inside all day and night, constantly pouring streams of digital light into your eyes, you’ll never develop normal circadian rhythms at all. Essentially you’ll live with permanent jet lag, and drastically increase your all-cause mortality risk.

Simply put: keeping the lights on at night will kill you slowly.

Let’s examine how.

Blue Light

Remember our friend from elementary school, Roy G. Biv? (Red, orange, yellow, green, blue, indigo, and violet?) Light exists across a spectrum of colors, and not all wavelengths have the same effect on our bodies.

Think of blue light as “energizing.” When you wake up in the morning and blue-wavelength light pours from the sky, it signals to your brain that it’s time to take action. It boosts your mood, reaction times, and your ability to focus on work. Blue light wakes you up.

Likewise, at sundown, when the sky turns red, it signals to your brain that it’s time for rest, relaxation, and recovery. If you’ve ever gone camping, you’ll understand this process intuitively. The yawns come quickly as evening turns to dusk. Washed in natural light all day, your body knows it’s time to sleep.

Now, imagine what happens if you crawl into the tent and stare at your mobile phone? Quickly, you’re wide awake again.

This is because our digital devices emit strong bursts of blue-wavelength light which tell our brains that it’s morning. In one study, Harvard researchers found that blue-light exposure suppressed melatonin production and shifted circadian rhythms by 3 hours on average. This was twice as long as “green light” exposure, and the exact opposite of red-light exposure which has no effect on sleep onset at all.

When our optic nerves perceive blue light after sundown, it sends mixed signals to the brain. Circadian rhythms get a little less rhythmic. Our pineal gland doesn’t produce melatonin. Your brain says to itself: “Stay alert! It’s daytime!”

For those of us who are particularly photo-sensitive, this can mean an immediate case of insomnia. For those who typically doze off easily, it means shallow sleep and waking up feeling tired.

In either case, the long-term health effects are worrying. Diabetes, heart disease, and obesity have all been linked to nighttime light exposure and its altering effects on circadian rhythms. For this reason, we think of our mobile phones as poison for our sleep.

Electric Light in General

When it comes to the causes of poor sleep, blue light isn’t the only culprit. In fact, any kind of electric light can make it difficult to fall asleep at night.

Just ask the Physicians for Human Rights who’ve exposed how shadowy government agencies use light exposure as a torture technique.

That’s right. Keeping your lights on at night is self-torture. By inducing sleep deprivation, it can cause extreme mental and physical harm in a very short timespan. Even at lower daily doses, the effects are so pernicious that researchers have been studying them anxiously for years.

What’s worse, electric light can lower the quality of your sleep…after you’re already asleep! According to the Sleep Foundation:

"Light exposure at night can hinder transitions between sleep cycles, reducing the quality of sleep. Too much light can cause repeated awakenings, interrupting the sleep cycle and reducing time spent in deeper, more restorative sleep stages."

It’s not just about falling asleep. Many folks claim they can fall asleep easily, even with bright lights on throughout the house and the television blaring. When they wake up groggy the next morning, and feel tired throughout the day, they never realize that their 100-watt lightbulbs prevent them from achieving true rest for hours after they’ve closed their eyes.

What are the health risks?

The scariest thing about light-induced sleep disruption is that it causes serious short- and long-term problems in people who are otherwise completely healthy.

In 2017, Dutch researchers reviewed a giant pile of existing studies to determine the effects of “sleep disruption.” They didn’t analyze sleep deprivation (or getting less than the recommended 8 hours). Instead, they wanted to understand the effects of altered sleep-cycles - the same effect created by electric-light exposure which we described above.

And the results were worrying.

In healthy adults, short-term sleep disruption caused:

• Increased stress response
• Somatic pain
• Reduced quality of life
• Emotional distress and mood disorders
• Cognitive, memory, and performance deficits

Long-term consequences included:

• Hypertension
• Dyslipidemia
• Cardiovascular disease
• Weight-related issues
• Metabolic syndrome
• Type 2 diabetes mellitus
• Colorectal cancer
• Increased all-cause mortality

It’s frightening to consider that sleep disruption, over the long-term, can have similar effects to the common health-destroying culprits which we all know to avoid: alcohol, tobacco, obesity, and more.

What steps should you take to minimize risk?

Step 1: Dim your electric lights after sundown, or turn them off completely. At the Hibernation Lab, we actually light candles after 9PM each night. Try to avoid light for two hours before you sleep. If bed time is 10:30PM, and you want to be asleep by 11:00, turn the lights off at 9:00.

Step 2: In the same two-hour timeframe, avoid looking at your mobile phone, computer screen, or television. Think of them as heavy doses of the blue light that we know is poison for your sleep.

Step 3: If you absolutely must use your phone or computer for work, consider blue light-blocking glasses. Sure, they look dorky. But they do a great job of minimizing exposure to those pesky “energizing” wavelengths of light.

Conclusion

The internal mechanisms that control our sleep-wake cycles are magnificent. They work in perfect harmony with the sun. But by fighting these mechanisms with harsh, unnatural electric light, we send mixed signals to our brains. Electric-light exposure at night can cause both shortened sleep duration and sleep disturbances. Over time, these effects compound and contribute to systemic disease and mortality.

Live the way nature intended for you, friend. Let the sun dictate your waking hours. Sleep naturally when the world goes dark. It’s absolutely essential to living a healthy life, and your body and brain will reward you for it.