Over the past decade, scientists have investigated whether artificial light – especially wavelengths of blue light – poses a risk to human health.
You may have heard that too many screens in the evening are bad for you, but the truth is that blue light emitted by devices such as phones and tablets can disrupt your dream.
But the blue light is not all bad – and here's why.
Blind mice feel blue light
In 2002, scientists identified a new type of photoreceptor cell in the eyes, when visually the blind mice that were studying were still able to respond to certain wavelengths of light.
Cells, called Intrinsicalli PhotoSensitive Retinal Ganglion Cells (ipRGCs), respond to light to regulate our circadian clock – not to form images such as sticks and cones in our eyes.
By revealing the amount of light in our environment, cells can communicate to our brain and body that it is day, or that it's time to sleep, which puts our circadian clock, says neuroscientist Stuart Peirson of the University of Oxford.
IpRGCs are the most sensitive to light wavelengths of 480 nanometers – directly in the blue light spectrum.
But Dr Peirson actually said, IpRGCs can detect most wavelengths of light, and all this can disrupt our circadian clock.
Disturb your circadian clock
In modern society, artificial light is comprehensive – and this happens with the expected cycle of light and the darkness of our bodies, says the psychology of Lora Vu from the University of Massy, which contributed to the report on blue light published this week by the Royal Society Te Aparangi in New Zealand.
"In our brains we have a masterclass, which is set by light exposure, and each organ and cell in your body have an internal clock," said Dr Vu.
These conflicting signals between your body watches can lead to changes in your physiology and behavior – for example, your mood and metabolism.
Shifting workers – who often need to sleep and eat in odd times – are the main candidates for circadian desynchrony.
Dr. Wu said that people are very difficult to adapt to such disorders, with one exception.
"Sometimes people think that if you are a permanent worker in a shift, you can essentially move your watch, then be awake and work at night and sleep during the day, but the only place where it is found is in offshore oil plants," she said
On offshore platforms, it is possible to have full control over the physical and social environment of workers, so their meals, light exposure and socialization are redirected to the night.
"In the case of [offshore rigs] you may see the adjustment in everyday life, "said Dr Vu.
When it comes to blue light, the time of your exposure is important to your health.
You can get this from daylight, of course.
But there is solid evidence that if you get too much blue light before sleeping from devices such as phones or tablets or from strong lights in a cool environment, it will hinder your body clock.
And that's because ipRGCs in your eye – that are very sensitive to blue light – tell your brain that it's not time to sleep.
Blue light and mental illness
Regulated exposure to artificial light has long been used to treat seasonal affective disorders (USA), while Dr Vu said that blue light therapy is a standard treatment for major depressive disorders.
"Adding artificial light to standard treatments for depression has proven to be really effective," she said.
People with mental health are more likely to have a disrupted daily rhythm, Dr Vu said, including sleeping during the day or staying late at night.
"We see a loss of rhythm in conditions such as a bipolar disorder, but also with the outcome of suicide – in the essence of any kind of behavior or mental illness," she said.
Since circadian rhythms of people with depression are diminished, exposure to blue light in the morning – as well as night restraint – can help to reset the body's natural rhythm, potentially improving sleep and mood.
Getting early nights can also help.
Australian research published earlier this year suggests that SSRI antidepressants were less effective for night owls, compared to early trails.
SSRIs or selective serotonin reuptake inhibitors work by enhancing the way your circadian clock responds to light, which should stabilize if you wake up and sleep in normal time.
But because night owls are exposed to higher light in the evening – often blue light on the screen – SSRIs can even lose their body clock and stop the treatment that works for basic mental health.
And poor sleep quality and lack of routine can contribute to poor physical and mental health by placing unhealthy cycles on the go.
In recognition of the link between the quality of sleep and good health, in September 2018, an investigation into the health awareness of sleeping in Australia was launched.
UV light is the right thing to do with eye disease
When you explore how blue light affects human health, the conversation inevitably turns into whether the blue light is detrimental to your eyes.
According to a report by the Royal Society Te Aparangi, while light exposure to high intensity can cause serious damage to the retina, blue light emitted from the phone and the computer is well below that harmful intensity.
The report also suggests that there is no evidence of the correlation between exposure to blue light and eye disease, including macular degeneration.
In 2017, it was reported that vitamin companies sold products claiming to protect children's eyes from the blue light emitted from their electronic devices – claims they dismissed as "ridiculous" by doctors' eyes.
People, especially parents, need to be more concerned about UV light, said ophthalmologist Shanel Sharma, a member of the Public Health Commission of the Royal Australian and New Zealand Ophtalmologists.
"Blue light gets a lot of attention, but it's not about eye disease," said Dr. Sharma.
Dr Sharma is a pediatric ophthalmologist in Sydney and regularly treats children with damaged eyes from UV radiation.
She said, while parents often think about protecting their children's skin, eye protection is not a priority.
Light up at night or go camping
There are some relatively slight changes that people can do with their behavior in order to reduce the risk of disturbing the body clock from blue light at night, said psychologist Dr. Vu.
"Try to get daylight in the morning, restrict the blue light from the device at night and replace the light-colored white / colored light bulbs with warmer colors," she said.
One study has shown that camping for the weekend and avoiding all artificial light sources can reset your circadian clock.
Camping is not a complete solution, of course.
But research supports the importance of the natural light-dark cycle in the regulation of our body.