A new study published in the journal PLOS Biology says the light humans experience in daily life heavily influences body rhythms, with around-the-clock access to electric lights combined with reduced exposure to natural sunlight leading to disruptions in sleep.
According to the study, the combination negatively impacts human health, well-being, and productivity.
The research also recommends how people should be exposed to bright light during the day and evening to contribute to healthy body rhythms, restful sleep, and daytime alertness.
What to know
An international team of scientists led by Timothy Brown, PhD, from the UK’s University of Manchester, and Kenneth Wright, PhD, from the University of Colorado Boulder, have put together what they say is one of the first evidence-based, consensus recommendations for healthy daytime, evening, and nighttime light exposure.
“These recommendations provide the first scientific consensus, quantitative, guidance for appropriate daily patterns of light exposure to support healthy body rhythms, nighttime sleep, and daytime alertness,” Brown said in a statement. “This now provides a clear framework to inform how we light any interior space, ranging from workplaces, educational establishments, and healthcare facilities to our own homes.”
The guidelines will be meant to help lighting and electronics industries design healthier environments and improve how we light homes, workplaces, and public buildings.
The researchers say light affects our daily patterns of sleep and alertness through a specialized cell in the eye using a light-sensitive protein called melanopsin, which is different from proteins in the eye’s rods and cones supporting vision (upon which traditional ways of measuring “brightness” are based).
Melanopsin is most sensitive to light residing in a specific part of the visual spectrum (blue-cyan light). The team developed a new light measurement standard tailored to this unique property called melanopic equivalent daylight illuminance.
Researchers analyzed data across a range of laboratory and field studies, which they say proved that the new measurement approach can reliably predict the effects of light on human physiology and body rhythms.
By doing so, it could allow the team to form widely applicable and meaningful recommendations as to how we should use — and not use — light in our daily lives.
The researchers say their next step will be integrating recommendations into formal lighting guidelines, which currently focus on visual requirements rather than light’s effects on health and well-being.
They expect increasing sophistication in LED lighting technology and the availability of low cost light sensors to increase the ease with which people can optimize their personal light exposure to best support their own body rhythms.
How screens can affect your health
A study published in the journal PNAS from the Center for Circadian and Sleep Medicine at Northwestern University Feinberg School of Medicine focuses on light’s negative effects on sleep and human health.
The researchers found that sleeping even just one night with a dim light, such as a TV set with the sound off, raised the heart rate and blood sugar levels of healthy young people.
The dim light entered the eyelids and disrupted sleep despite the subjects being asleep with their eyes closed.
The study pointed out that heart rate typically drops at night, slowing down as the brain repairs and rejuvenates the body. Numerous studies have shown that an elevated heart rate at night can be a risk factor for future heart disease and early death.
“The results from this study demonstrate that just a single night of exposure to moderate room lighting during sleep can impair glucose and cardiovascular regulation, which are risk factors for heart disease, diabetes, and metabolic syndrome,” the study’s author and the school’s chief of sleep medicine, Phyllis Zee, MD, PhD, told Northwestern Now. “It’s important for people to avoid or minimize the amount of light exposure during sleep.”
The Northwestern team recommended not turning any lights on while sleeping. If you need to have a light on (for example, for safety reasons) make it a dim light that is closer to the floor.
They also said the light’s color is important.
Amber or a red-orange light is less stimulating for the brain. Don’t use white or blue light, and keep light far away from the sleeping person.
They also recommend blackout shades or eye masks for people who can’t control outdoor light, and you should move your bed so the outdoor light isn’t shining on your face.