Night-shift nursing staff would be happier working under red lights, rather than white or blue, new research suggests.
US scientists found that exposure to blue light at night can depress night-shift workers, white lowers moods less, while red is the least disturbing colour, according to US scientists.
Researchers, who say their findings gained from tests on hamsters would also be applicable to humans, suggest the results have vital implications for nurses and other night-shift staff.
They claim that round-the-clock workplaces should ideally be red lit at night.
Head researcher Professor Randy Nelson, from Ohio State University, said: “Our findings suggest that if we could use red light when appropriate for night-shift workers, it may not have some of the negative effects on their health that white light does.”
Scientists subjected hamsters to nights with no light, or lit by low-level red, white or blue light.
The rodents were then tested for depressive symptoms.
One sign that hamsters are unhappy is that they lose interest in sugar water, which they usually enjoy.
The findings revealed that hamsters left in the dark at night for a month consumed the most sugar water, followed by those exposed to red light.
White light seemed to drop the animals’ mood, and blue light depressed them even more.
Rodents that spent nights in blue or white light had substantially fewer dendritic spines than those exposed to complete darkness or red light.
Dendritic spines are hair-type growths on brain cells that are used to transfer chemical signals.
Reduced dendritic spine density has previously been associated with depression.
Co-author Dr Tracy Bedrosian, also from Ohio State, said light at night may have unwanted effects on mood-regulating brain regions.
People could benefit from avoiding the blue and white glow of computers, televisions and other electronic devices at night, said the researchers.
The results are published in The Journal of Neuroscience.
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