The modern bedroom is full of lights, from glowing computer monitors and clock radios to any number of blinking and glimmering electronic devices. Trouble is, chronic exposure to light at night leads to a host of health problems.
To understand why chronic exposure to light at night is so bad, we need to consider human evolution. Prior to the end of the stone age, humans were exposed to two different kinds of natural light responsible for regulating circadian rhythmicity. During the day we had the sun, while at night we had the moon and the stars, and perhaps the light from campfires. The binary day/night pattern was unrelenting, and our biological programming followed suit.
Related:
This is why you aren't sleeping right
So it’s true! The full Moon does mess with our sleep.
Today, we have artificial lighting at night (LAN), and it's a different case altogether. Indoor lighting is considerably less powerful than sunlight, but many orders of magnitude greater than star and moonlight. Check out this chart to see what I mean:
Keep in mind that this is a logarithmic scale, so the difference between sunlight and moonlight is considerable — a difference that influences a series of critical biochemical cascades tied to light periodicity, including the production of cortisol and melatonin levels.
Light is a Drug
Melatonin suppression is key to understanding much of why LAN is so crappy for us. This workhorse biochemical is produced by the brain's pineal gland at night — when it's dark — to regulate our sleep-wake cycle. It lowers blood pressure, glucose levels, and body temperature — key physiological responses responsible for restful sleep. As neurologist George Brainard puts it, "Light works as if it's a drug, except it's not a drug at all."
The part of your brain that controls your biological clock is the Suprachiasmatic Nucleus (SCN), a group of cells in the hypothalamus. These cells respond to light and dark signals. The optic nerves in our eyes senses light and transmits a signal to the SCN telling the brain that it's time to wake up. It also kickstarts other processes, like raising body temperature and producing hormones like cortisol. Our cortisol levels are relatively low at night, allowing us to sleep, and higher during the day, allowing for the stabilization of energy levels and the modulation of immune function.
But LAN unnaturally elevates cortisol levels at night, which disrupts sleep and introduces a host of problems relating to body-fat levels, insulin resistance, and systemic inflammation. It also contributes to sleep debt and a disruption the neuroregulation of appetite.
But if our rooms are dark at night, there's no optic signal to the SCN, so our bodies pump out the much needed melatonin. Moreover, our melatonin levels are regulated according to the amount of exposure we had to light during the previous day.
Related:
The science behind power naps and insomnia.
The science behind power naps, and why they're so damn good for you
The Light Before You Sleep
Indeed, studies have shown that exposure to room light before bedtime shortens melatonin duration by about 90 minutes compared to dim light exposure. In addition, exposure to room light during usual hours of sleep suppresses melatonin levels by more than 50%. That's significant.
So, even before you hit the hay, the light in your bedroom is causing you problems. With the introduction of tablets, smartphones, and energy-efficient light bulbs, it's an issue that's only getting worse.
And just to add insult to injury, many modern devices emit blue light from light-emitting diodes (LEDs) — light that's especially good at suppressing melatonin . This is because melanopsin — a photopigment found in specialized cells of the retina involved in the regulation of circadian rhythms — is most sensitive to blue light .
Recently, scientists warned college students about the impact of light from computer monitors on melatonin levels . They found that computer light at night — particularly blue light that was scanned by wearing different wavelength-blocking glasses — reduces college students' melatonin levels. A related study found that backlit tablet displays suppress melatonin , disrupting sleep. But the researchers write: "[It] is important to acknowledge that usage of self-luminous electronic devices before sleep may disrupt sleep even if melatonin is not suppressed. Clearly, the tasks themselves may be alerting or stressful stimuli that can lead to sleep disruption." Which is a very good point.
Related:
Reading on your tablet computer at night could be disrupting your sleep
The Cancer Link
Regrettably, all this hormone and biochemical disruption is creating downstream effects — cancer being one of them. Scientists aren't entirely sure why, but studies consistently show a correlation.
For example, a 10-year study found that a sample group of over 1,670 women exposed to higher intensity light in their sleeping environment had 22% higher odds of developing breast
To understand why chronic exposure to light at night is so bad, we need to consider human evolution. Prior to the end of the stone age, humans were exposed to two different kinds of natural light responsible for regulating circadian rhythmicity. During the day we had the sun, while at night we had the moon and the stars, and perhaps the light from campfires. The binary day/night pattern was unrelenting, and our biological programming followed suit.
Related:
This is why you aren't sleeping right
So it’s true! The full Moon does mess with our sleep.
Today, we have artificial lighting at night (LAN), and it's a different case altogether. Indoor lighting is considerably less powerful than sunlight, but many orders of magnitude greater than star and moonlight. Check out this chart to see what I mean:
Keep in mind that this is a logarithmic scale, so the difference between sunlight and moonlight is considerable — a difference that influences a series of critical biochemical cascades tied to light periodicity, including the production of cortisol and melatonin levels.
Light is a Drug
Melatonin suppression is key to understanding much of why LAN is so crappy for us. This workhorse biochemical is produced by the brain's pineal gland at night — when it's dark — to regulate our sleep-wake cycle. It lowers blood pressure, glucose levels, and body temperature — key physiological responses responsible for restful sleep. As neurologist George Brainard puts it, "Light works as if it's a drug, except it's not a drug at all."
The part of your brain that controls your biological clock is the Suprachiasmatic Nucleus (SCN), a group of cells in the hypothalamus. These cells respond to light and dark signals. The optic nerves in our eyes senses light and transmits a signal to the SCN telling the brain that it's time to wake up. It also kickstarts other processes, like raising body temperature and producing hormones like cortisol. Our cortisol levels are relatively low at night, allowing us to sleep, and higher during the day, allowing for the stabilization of energy levels and the modulation of immune function.
But LAN unnaturally elevates cortisol levels at night, which disrupts sleep and introduces a host of problems relating to body-fat levels, insulin resistance, and systemic inflammation. It also contributes to sleep debt and a disruption the neuroregulation of appetite.
But if our rooms are dark at night, there's no optic signal to the SCN, so our bodies pump out the much needed melatonin. Moreover, our melatonin levels are regulated according to the amount of exposure we had to light during the previous day.
Related:
The science behind power naps and insomnia.
The science behind power naps, and why they're so damn good for you
The Light Before You Sleep
Indeed, studies have shown that exposure to room light before bedtime shortens melatonin duration by about 90 minutes compared to dim light exposure. In addition, exposure to room light during usual hours of sleep suppresses melatonin levels by more than 50%. That's significant.
So, even before you hit the hay, the light in your bedroom is causing you problems. With the introduction of tablets, smartphones, and energy-efficient light bulbs, it's an issue that's only getting worse.
And just to add insult to injury, many modern devices emit blue light from light-emitting diodes (LEDs) — light that's especially good at suppressing melatonin . This is because melanopsin — a photopigment found in specialized cells of the retina involved in the regulation of circadian rhythms — is most sensitive to blue light .
Recently, scientists warned college students about the impact of light from computer monitors on melatonin levels . They found that computer light at night — particularly blue light that was scanned by wearing different wavelength-blocking glasses — reduces college students' melatonin levels. A related study found that backlit tablet displays suppress melatonin , disrupting sleep. But the researchers write: "[It] is important to acknowledge that usage of self-luminous electronic devices before sleep may disrupt sleep even if melatonin is not suppressed. Clearly, the tasks themselves may be alerting or stressful stimuli that can lead to sleep disruption." Which is a very good point.
Related:
Reading on your tablet computer at night could be disrupting your sleep
The Cancer Link
Regrettably, all this hormone and biochemical disruption is creating downstream effects — cancer being one of them. Scientists aren't entirely sure why, but studies consistently show a correlation.
For example, a 10-year study found that a sample group of over 1,670 women exposed to higher intensity light in their sleeping environment had 22% higher odds of developing breast
