Updated: May 4, 2021
These are the four requirements for life as we know it. Without them (in various lengths of time) people cannot survive. Sleep is a crucial factor as it profoundly influences our performance at work, our risk for chronic disease, illness, and our overall quality of life.
Sleep researchers aren’t clear on the exact reason or mechanism why humans even need to sleep to begin with. From an evolutionary perspective, the act of sleeping would certainly have left primitive humans vulnerable to attack so it must offer some great advantage.
In general terms, sleep is thought to allow our brains and our bodies to mend and repair from the damage and stressors of the day; synaptic plasticity is managed, brain pathways that are not being used are pruned and altered, muscles are repaired, and energy stores are replenished. All of this to prepare us for the following days tasks.
People Are Tired
Short sleep duration (defined as less than 7 hours of sleep per night) is extremely common and 24% – 48% of people report it.
If you are obese, a smoker, consume excessive amounts of alcohol, or are not physically active you are more likely to report short sleep duration.1
Sleep is an active process for humans. In other words, you don’t fall asleep simply because your brain is “fatigued”. Sleep is actively maintained throughout the night. Disruption of this careful balancing act between being awake and sleep results in, what else, disrupted sleep.
Circadian Rhythm is Important
People display a 24-hour cycle known as circadian rhythm. This rhythm is endogenous meaning it is maintained even in the absence of environmental cues. Human beings placed environments without light, time, or social queues, will still display a 24-hour rhythm. However, external timing cues do modulate and adapt the rhythm to the environment.
Sunlight for people is a powerful cue to have the waking phase of our 24-hour cycle during the day. Various other mammals, like rats and mice, have most of their waking phase at night.
These rhythms were created through many years of evolutionary pressure and adaptation. Light cues, which modulate our circadian rhythm, are extremely powerful. Circadian rhythm is endogenous so an internal pacemaker is required.
From an anatomical perspective the suprachiasmatic nucleus in the hypothalamus is a major part of the internal pacemaker of humans. This part of the brain is connected to the retina via the retinohypothalamic tract.2 This powerful connection to the brain and shows just how important light is for controlling circadian rhythm.
Stages of Sleep
Sleep is divided into two categories – non-REM and REM (Rapid Eye Movement)
Non-REM sleep is subdivided into 4 stages, each with its own properties and benefits. During non-REM sleep neuronal activity is low, metabolic rate and brain temperature are at their lowest, heart rate decreases, blood pressure lowers, and muscle tone and reflexes are intact.
In REM sleep the brain activity is similar to that of the awake brain. For this reason, it is sometimes referred to as paradoxical sleep. In REM sleep brain temperature and metabolic rate rise and there is complete loss of muscle tone with the exception of the diaphragm (so you can breathe), and certain inner ear and eye muscles.
The Negative Effects of Blue Light
A study of about 1,500 people found that 90% of adults use an electronic device within 1 hour of bedtime at least a few times per week.
Devices may be an important factor to insomnia because of the short-wavelength-enriched light that is emitted from them. Exposure to light in the evening and the early part of the night, even at low intensity, has several sleep-disturbing effects. First is suppresses melatonin delaying the onset of sleep. It shifts the circadian clock to a later time making it harder to fall asleep at a regular hour by increasing alterness.3
In one fascinating study, 12 people were randomly assigned reading from an E-Book for 4 hours before bed or reading from a print book for 4 hours before bed for 5 consecutive evenings.
They found that those reading an E-book displayed decreased subjective sleepiness, decreased EEG delta/theta activity, suppressed melatonin secretion, increased time to fall asleep, delayed and reduced REM sleep, and reduced morning alertness.3
Why does blue light have this effect on people?
Our eyes have rods, cones, and intrinsically photosensitive retinal ganglion cells. Rods and cones are mostly responsible for image creating vision. Intrinsically photosensitive retinal ganglion cells are used for regulating circadian rhythm and other biologic functions. Retinal ganglion cells form the beginning of the retinohypothalamic tract which transmits light data from the retina to the hypothalamus to regulate circadian rhythms.
These retinal ganglion cells respond to short-wavelength light (blue coloured light) which is emitted from most electronic devices.
This blue light will cause a high rate of fire from the eyes to the hypothalamus, which will change our body’s hormonal and circadian rhythms.4 Blue light also has the ability to stimulate other areas of the brain which are responsible for producing norepinephrine, a neurotransmitter that has potent excitability properties.5
Since we know blue light emitted from almost all devices and is disruptive to the pathways for sleep, it’s important to take steps to fix his if you’re having trouble sleeping.
Here are a few easy steps to take:
Do not use your device in bed.
Avoid using it at least an hour before you plan to go to bed.
Do not watch TV in bed either.
If you have to use a device for some reason, avoid long exposure.
Majority of new devices come with a night-shift mode. This mode shifts the hue of the screen to a warmer, redder tone. This has been studied to see if it offset the negative effects of the light on our rhythm. Unfortunately, melatonin levels were still reduced when using night shift mode.6
In the end, if you suffer from difficulty sleeping, staying asleep or insomnia, reducing your device exposure could have a measurable effect on your sleep. Our devices have become extensions and links of our lives so it may be difficult to completely eliminate exposure at night, however, your brain and body will thank you for the better sleep.
2Kandel, et al., editors. “Sleep and Dreaming .” Principles of Neural Science, 4th ed., McGraw-Hill, 2000, pp. 936–947.
3Proc Natl Acad Sci U S A. 2015 Jan 27;112(4):1232-7.
4Molecular Vision 2016; 22:61-72.
5Blue-Light Therapy following Mild Traumatic Brain Injury: Effects on White Matter Water Diffusion in the Brain. Front. Neurol. 8:616.
6Sleep, Volume 40, Issue suppl_1, 28 April 2017, Pages A290.
Dr. Mike Hadbavny
Chiropractor, Sports Sciences Resident RCCSS(C)
If you are interested in learning more about how chiropractic care can be effective for your particular condition or health goals, contact Dr. Mike Hadbavny at 250-881-7881 today to make an appointment and discover the many benefits of seeing a chiropractor in Victoria BC. Contact us today.