Lighting color affects sleep and wakefulness

June 8, 2016
Credit: Vera Kratochvil/public domain

A research team from Oxford University have shown how different colours of light could affect our ability to sleep.

The researchers, led by Dr Stuart Peirson from Oxford's Sleep and Circadian Neuroscience Institute were aiming to understand why exposing mice to bright light caused two - physically incompatible - responses.

Dr Peirson explained: 'When we expose mice to light during the night, it causes them to fall asleep. Yet, at the same time, it also increases levels of corticosterone, a stress hormone produced by the adrenal gland that causes arousal - wakefulness. We wanted to understand how these two effects were related and how they were linked to a -sensitive pigment called melanopsin, known to play a key role in setting our body clock.'

The team exposed mice to three different colours of light - violet, blue and green. Based on the existing data about the role of melanopsin in , they expected that the blue light would induce sleep fastest as the wavelength of the blue light (470 nanometres - nm) was closest to the peak sensitivity of the pigment (around 480nm).

However, it was green light that produced rapid sleep onset - between 1 and 3 minutes. Blue and violet light delayed sleep - the onset of sleep taking between 16 and 19 minutes for blue and between 5 and 10 minutes for violet.

Dr Peirson said: 'The results meant that mice exposed to blue light had less sleep than those exposed to violet and green light. We confirmed the effect by testing mice using green and blue light at a time when they would usually be less active.'

To investigate the role of melanopsin, the team performed the same test on mice lacking the pigment. For these mice, the colours had opposite effects - blue caused rapid sleep onset, while green and violet significantly delayed sleep, showing that melanopsin is necessary for the substantial wavelength-dependent effects of light on sleep.

The researchers also found that while exposure to all three colours of light increased the level of corticosterone stress hormone in ordinary mice, blue light caused a much higher rise. In mice without melanopsin, the response to blue light was greatly reduced. Blocking the effect of corticosterone reduced the sleep-delaying effect, suggesting that the production of this hormone in response to light actively inhibits sleep.

Dr Peirson said: 'This study shows that there are different pathways from the eye to the brain - one directly regulating sleep and the other increasing arousal. Melanopsin has a more complex role than previously thought, affecting both pathways. This is the first time that it has been shown to regulate adrenal stress responses.

'An obvious caveat of this study is that are a nocturnal species that are active during the night. As such, may be expected to increase wakefulness rather than increasing sleep in humans. We would therefore predict that blue light will further enhance the wake-promoting effects of light by elevating adrenal .

'The results also add to our understanding of the effects of light emitting devices on humans, where recent studies have shown that the blue light from these devices delays sleep. However, as we have shown that there are different pathways in the brain, by which different colours of light have different effects on sleep or wakefulness, we need to understand how the overall colour balance of artificial could affect people's alertness and sleep.'

Explore further: Pre-surgical exposure to blue light reduces organ damage in mice

More information: Melanopsin regulates both sleep-promoting and arousal-promoting responses to light, PLOS Biology, DOI: 10.1371/journal.pbio.1002482

Related Stories

Pre-surgical exposure to blue light reduces organ damage in mice

April 25, 2016
A 24-hour exposure to bright blue light before surgery reduces inflammation and organ damage at the cellular level in a mouse model, according to new research from the University of Pittsburgh School of Medicine.

Bright light and caffeine improve driver alertness

March 29, 2016
Caffeine and blue-green light have significant effects on improving the driving performance of chronically sleep deprived young people, an innovative QUT study has found.

Video: What you need to know about sleep

March 21, 2016
Dr. Alon Avidan, a professor of neurology and director of the UCLA Sleep Disorders Center, offers these tips for getting better sleep:

Study links evening blue light exposure to increased hunger

June 2, 2014
A new study suggests that blue-enriched light exposure immediately before and during the evening meal may increase hunger and alter metabolism.

Can't sleep? Street lights may be keeping you awake

March 1, 2016
If your neighborhood is well-lit at night, you may not be sleeping well, according to a study released today that will be presented at the American Academy of Neurology's 68th Annual Meeting in Vancouver, Canada, April 15 ...

Recommended for you

High-fat diet in pregnancy can cause mental health problems in offspring

July 21, 2017
A high-fat diet not only creates health problems for expectant mothers, but new research in an animal model suggests it alters the development of the brain and endocrine system of their offspring and has a long-term impact ...

To combat teen smoking, health experts recommend R ratings for movies that depict tobacco use

July 21, 2017
Public health experts have an unusual suggestion for reducing teen smoking: Give just about any movie that depicts tobacco use an automatic R rating.

Opioids and obesity, not 'despair deaths,' raising mortality rates for white Americans

July 20, 2017
Drug-related deaths among middle-aged white men increased more than 25-fold between 1980 and 2014, with the bulk of that spike occurring since the mid-1990s when addictive prescription opioids became broadly available, according ...

Aging Americans enjoy longer life, better health when avoiding three risky behaviors

July 20, 2017
We've heard it before from our doctors and other health experts: Keep your weight down, don't smoke and cut back on the alcohol if you want to live longer.

Parents have critical role in preventing teen drinking

July 20, 2017
Fewer teenagers are drinking alcohol but more needs to be done to curb the drinking habits of Australian school students, based on the findings of the latest study by Adelaide researchers.

Fresh fish oil lowers diabetes risk in rat offspring

July 19, 2017
Fresh fish oil given to overweight pregnant rats prevented their offspring from developing a major diabetes risk factor, Auckland researchers have found.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.