Light and the body
The effect of light on the human body has been a fascination for decades. Many a scientist and research team has looked at various aspects of this, asking many a question. Through these questions and findings, many more continue to surface as more definitive answers become necessary.
Are we jeopardising our health by digitally fiddling with light processes and the way artificial light is used? Is blue light in itself that bad? Or is the problem perhaps in the timing of use?
Before there was ever such a thing as artificial lighting, sunlight was our primary source of light. Evenings were spent in relative darkness. As new technology develops and fiddles with lighting, so our evenings as a human race have become very much illuminated. This has had a profound influence on our body’s ‘biological clock’ (circadian rhythm), but at what price tag?
Where we’ve gone wrong is in the development of habits and uses of light (blue light) that disrupt its natural rhythm. One of the potential adverse health effects of this is how it affects our quality of sleep. But many researchers have raised startling concerns over more serious health conditions which may have direct causal influences in the development of certain cancers (specifically breast and prostate cancer), problems with obesity, heart disease and diabetes.
Colours of light influence its different effects. It has been researched and proved that blue wavelengths are at their most beneficial during daylight hours. When the influences include the boosting of attention span, mood and reaction times, blue light doesn’t sound like such a bad thing at all.
It’s when research conducting various tests look at night-time effects, that blue light appears to have adverse effects, and become disruptive to the body. The reason why research has focussed so much attention on blue light usage at night is because of our increasing exposure to it. Electronic devices with screens are virtually everywhere. We’ve also developed an increasing amount of energy-efficient lighting technologies (such as fluorescent bulbs and light-emitting diodes / LEDs), which also contribute to more frequent exposure to blue wavelengths once the sun goes down.
What is a circadian rhythm?
In simple terms, it’s something like the body’s proverbial clock. Basically, it is an endogenously generated physiological process which operates in an approximate 24-hour cycle. This rhythm is sensitive to external cues such as sunlight (or any light) and temperature.
It should be noted that as a species, human beings have slightly varied circadian rhythms. The average length has been estimated at 24 and one quarter hours. Previous studies of circadian rhythm have shown that daylight influences a person’s ‘internal or biological clock’.
The average estimation applies to a vast chunk of the human race. Early birds have rhythms short of the average mark and night owls have slightly longer rhythms.
How does light affect the body?
Light (daylight specifically) effectively synchronises our circadian rhythm. Cells in the retina of the eye are finely-tuned to short-wavelength light, sending response signals to the brain. This signals them prompts the brain to reduce the pumping out of melatonin in the body, which induces drowsiness (i.e. sleep). The brain then also begins producing more cortisol and ghrelin – the hormones which effectively wake us up in the morning and induce hunger.
Naturally, melatonin levels are supposed to decrease and increase in cycles (between dusk and dawn). When increased, this hormone effectively prepares the body for rest, which is essential for our wellbeing. When melatonin levels rise, our body temperature drops, hunger subsides and sleepiness increases. Whether we are asleep or not, this effect is restorative.
Modern times are tampering with the natural transition of night-time physiology, delaying the process and interrupting circadian rhythm. We have now become, what some have described as, ‘darkness deprived’. Why? In some ways, we ‘bathe ourselves in light’.
This in itself has been studied repeatedly, with some researchers linking light exposure and night shift work with various health conditions. The exact causal reasons, however are not entirely clear. What researchers are sure of is that the body does not fare well with too much light exposure in a 24-hour period. Excess light exposure suppresses the excretion of melatonin. With this as a base to work from research is still being done to try and explain how this lowered secretion may have an influence on the development of cancer.
Diabetes and obesity are also thought to be linked. Research has since shown that when participants gradually shifted their circadian rhythms, their blood sugar levels increased and resulted in a prediabetic condition. Leptin levels (a hormone) decreased at the same time. Dim light was also tested, which showed influences on circadian rhythm and melatonin secretion too.
Stephen Lockley, a Harvard sleep researcher believes that more exposure to light at night is one of the main reasons people are not getting adequate sleep. In his opinion, cardiovascular and diabetic problems are not the only concern as a result – increased risk for depression should also be added to the list.
Did you know? Approximately 80% of melatonin is produced in the gastrointestinal tract (G.I. tract) in the body.
Is blue light all that bad for health and wellbeing?
Any light exposure at night can influence the secretion levels of melatonin. Harvard University researchers have found over the years, that blue light does so too, and more powerfully. In research testing, comparable brightness levels of both blue and green light exposure were assessed (up to 6.5 hours of exposure each). Blue light resulted in melatonin suppression for twice as long as did green light, and shifted circadian rhythms by twice as much too. Where green light had an interference impact of 1 and a half hours, blue light showed a 3-hour difference.
Many a study has been done, introducing different variables and addressing all sorts of questions (even the testing of eyewear that blocks blue light), and most conclude the same – blue light is a potent suppressor of melatonin.
Why has this raised alarm bells?
Technological advancements are continuously developing a serious dependency on devices that promote screen time, and especially so during night time hours. Modern society is virtually consumed by screens – in the workplace, in the home and integrated with overall lifestyle, everywhere we go. TVs, mobile phones, tablet devices… you name it. Modern lifestyle is doing more to promote ‘staring into the depths of technology for hours’ than it isn’t.
So, what’s the problem? In short, blue light, and all of its potential side-effects. There’s a good side to blue light, however. It may come down to the timing of use.
Natural blue light radiates from the sun. This natural process is important to maintain our circadian rhythm and keep it functioning as it should each and every day. In essence, it is this blue light that strongly influences and regulates our sleep and wake cycles every 24 hours.
Research has indicated that we, due to modern lifestyle, are becoming increasingly overexposed to blue light through increased computer usage, TV watching and use of mobile phone screen time. This is thus impacting our natural sleep and wake cycles and having adverse effects, overall, on our general alertness and wellbeing.
For nearly a decade, research has been toying with the adverse effects of blue light overexposure. Not only the general public living a regular lifestyle are showing signs for concern. Even those in the medical field, such as doctors and nurses who do shift work in medical facilities are affected. One such concern is the increased risk for melanoma (a severe form of skin cancer).
How is overexposure a cause for concern?
Exposure to blue light at inappropriate times for the body tricks it into ‘thinking it is meant to be awake’ and effectively disrupts the cycle flow. Physically, the body doesn’t sufficiently prepare for slumber and impacts the quality of sleep we are able to get. Even if you are managing to get in 8 hours of sleep overnight, the quality may be lacking and thus means that it will prove difficult to function properly in the day ahead.
The impact of disrupting the body’s natural biological clock (physiological process) affects not only sleeping and feeding cycles, but also brain activity, cell regeneration and hormone production. Effectively, overexposure confuses the hypothalamus in the brain – it simply doesn’t know how to operate seamlessly.
When we add needless amounts of additional artificial light exposure, we cut into the natural sleep cycle by allowing the retina to receive light and transmit brain messages for hormone suppression and production at any time of day. The body doesn’t know when to actually get ready for sleep.
Fluorescent and LED lighting not only provides artificial light to cause disruption, but also blue light too. The purpose of LEDs and fluorescent bulbs is to provide more energy efficiency. These bulbs also provide better lighting than incandescent bulbs. Many appliances and technological devices and products make use of these bulbs too.
Products with these bulbs, such as TVs, tablets and smartphones, produce blue light wavelengths that effectively influence out attention spans, mood and reaction times. During the day, when we are at our most alert, this is more of a positive influence. At night, it breaks the cycle flow. The shorter wavelengths of blue light stimulate the suppression of melatonin. At night, we are far more sensitive to the effects of blue light.
A professor and circadian rhythms expert at the Texas A&M Health Science Center College of Medicine, David Earnest, says that the spectrum of wavelengths has a definite influence on the human circadian system.
"Blue light is the most sensitive side of the spectrum," he says.
Blue wavelengths suppress delta brainwaves and boost alpha wavelengths (i.e. those that induce sleep are suppressed and those that influence alertness are boosted).
Is sending off that last batch of emails at night really something we need to think twice about?
A growing number of researchers think so, yes. PhD, MD, chief of the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital in Boston, Charles Czeisler adds his name to the growing list too and believes that it should be of greater concern to the public.
“The more research we do, the more evidence we have that excess artificial light at night can have a profound, deleterious effect on many aspects of human health,” he says.
E-readers, mobile phones, tablets, laptops, TVs and various household appliances and eco-friendly street lamps… all emit shorter, brighter bluish wavelengths and light that is brighter. When it comes to overall health, Czeisler believes that it is just as important to better manage blue light exposure at night as it is to take the best care when it comes to our nutritional and exercise regimes. We’re compromising it all by influencing restorative sleeping habits in a negative way.
Studies and workshops looking into the effects have been countless. All have looked at the influences on problems with sleep, but have also found linked to issues with weight gain, cancer, heart disease and depression. Many claims continue to be made, showing growing concern for the risk of other chronic health conditions.
The majority of claims, however, have either been assessed based on animal studies or from larger populations, showing distinctive patterns. As yet, a direct cause and effect is still to be conclusively determined.
Does that mean we shouldn’t yet pay attention to the alarm bells? The number of health experts in agreement is still growing. Many appear adamant that even without a direct causal link, the result patterns show enough to take seriously and warrant steps to correct now.
Some organisations are taking steps. For instance, in October 2016, NASA implemented a change in lighting at the International Space Station (ISS) which automatically dimmed light at night, emitting longer-wavelength light instead.
Experts all agree, it’s not that complicated a solution either. Dim lights at night and tone down on blue light exposure. There’s little harm during the day. It’s night-time exposure that should be taken more seriously. Allowing the kids, one last game on the tablet before bed-time or quickly shooting off a batch of mails to finish out the day may seem harmless, but research findings are suggesting there may be long-term health effects.
The first indication that blue light may be affecting our health was short-term sleep disruption. This arose from a study that placed participants in a sleep laboratory, allowing access to read an e-reader at night for 5 days. Findings saw that melatonin levels decreased by 55%. Along with that, participants took longer to fall asleep and experienced poor REM (rapid eye movement) sleep. All felt somewhat groggy the following morning. This was compared to participants who read a newspaper or a book before bedtime, providing a strong hint that the light emitted from an e-reader has an effect on the quality of sleep.
Studies have also assessed teenagers who appear to be sensitive to light during the night. Participants were allowed an hour of exposure from mobile / tablet devices. Findings showed melatonin levels lowered by 23%. When usage time was increased to 2 hours, melatonin levels dropped further (38%).
When it was noted that blue light may influence our natural hunger cycles as well, investigations continued, looking for ways it may be fuelling metabolic diseases and weight gain. Why? Study participants who were exposed to bright light (blue light) at night appeared hungrier and produced less insulin. This means that ‘late-night snacks’ are more easily stored as fat in the body and can increase the likelihood of diabetes.
Obesity came under the spotlight too. In March 2016, a group of researchers from the University of Haifa, Israel, conducted a comparison of data with that of the WHO (World Health Organization). The comparison looked at obesity data and night-time military satellite images (showing lighting). The comparison found similarities between the most night-time illuminated areas and number of obese individuals.
Where children are concerned, studies have made use of animal testing. The Ohio State University found a measurable impact on the brain whereby inflammation increased and hormones needed for promoting new brain cell growth considerably decreased with bright light exposure just 3 feet away. Researchers noted a strong possibility for ‘depressive-like symptoms’ and concerns with memory function as a result.
What about children with existing medical conditions? Those with autism and Attention Deficit Hyperactivity Disorder (ADHD) should be taken into consideration too. Many with these conditions also experience gastrointestinal issues. Overexposure to blue light biologically inhibits the production of melatonin in the bodies of affected individuals and thus affects circadian rhythms, which in turn can make for difficult treatment programmes.
Many parents of children with these conditions utilise screen time as a reward. If a child accomplishes a task or chore successfully, they are then allowed set time using a device such as a tablet. Parents will need to better understand the relationship between blue light and melatonin, especially when coping with an autistic or ADHD affected child. The reward is likely overriding positive effects of treatment to better regulate the body and promote better overall health and functionality.
Studies have also looked at specific populations, including emergency care workers and oilfield workers. Both are chronically exposed to bright light at night. They too showed similar mood impairments and concentration issues to those exhibited in the tested animals.
Chairman of the department of neuroscience at Ohio State University and study author, Randy Nelson sums the findings up as follows, “This is not just a sleep problem. This is a problem of disruption of the entire circadian clock, and sleep is just one hand of that clock.”
Findings from studies have also noted a dramatic risk increase for breast cancer in women – between 50% and 70%. Why? Melatonin is a known anti-cancer agent. Lower levels in the blood stream for female night shift workers places them at higher risk of developing cancer during their lifetime.
With increased blue light exposure at night in the average city / suburban home, are we all effectively ‘becoming night shift workers?’
Experts do agree that although there has been a considerable amount of research, it is still in its infancy. It’s still enough to take note of, however, in order to try and prevent long-term damage.
What should you do?
If blue light and energy-efficient lighting is at odds with our personal health and well-being, how can we take matters into our own hands and correct the situation?
It’s a lot simpler to reduce blue light exposure than we think. Some steps include:
- Switch fluorescent or LED lights (on the blue spectrum) for dim red lighting - Red lighting has the least effect on the body’s circadian rhythm and melatonin cycles. This is best set up in your place of rest – your bedroom. Dimming switches (with longer wavelength lights) in other areas of the home, including the bathroom, can also help minimise effects of artificial and blue light.
- Make use of technology to influence light exposure – Technology has cottoned on too and developed applications which can be used to automatically switch blue light on screens to that of orange-red longer wavelength light. Applications such as f.lux and eye care browser can be downloaded and set to make use of screens less harmful on the eyes, and body clock as a whole.
- Be more mindful of bright screens before bedtime – Ensure that you discontinue exposure to bright screens at least 1 to 3 hours before heading to bed. No TV, tablets, smartphones, computers or e-readers.
- Use blue light (and light in general) more effectively during the day – Lots of exposure during the day can help to promote better sleep at night, as well as enhance your mood and level of alertness during daylight hours. The effects will surely help cultivate a healthier body clock. If lighting in your place of work is insufficient, the body won’t be at its best either. A dim environment will not adequately stimulate positive effects (alertness etc.). Make use of natural light as well – take a walk or ensure that the environment where you spend the most time during the day has ample light. Move your desk near a window if you must.
- Blue-blocking glasses for night-shift workers – Studies have found these to be effective, not only for those working night-shift jobs, but also those who spend a lot of time using electronic devices at night.