Different lights affect our moods and attentiveness differently. They also cause a shift in our circadian rhythms and sleep patterns.
Human beings have a biological clock controlled by circadian rhythm. It is roughly 24 hours and 15 minutes long. Our exposure to daylight keeps that clock synchronised to the external timing.
A hormone called melatonin regulates our circadian rhythm. As we approach sleep time, a gland in our brain called the pineal gland increases melatonin secretion, which makes us feel more sleepy.
When any light falls on the eye retina, its rays generate electrical impulses in the retinal cells that signal to the pineal gland to reduce the production of melatonin.
Since ancient times, as the sun goes down in the evening, melatonin production gets kickstarted. Before the advent of modern lights, the melatonin secretion went uninterrupted till bedtime. However, these days, we suffer from light pollution with ever brighter lights illuminating our world.
Seeing blue lights deceives the pineal gland into believing that daylight has come about and so it reduces melatonin production making one alert and attentive. However, if this happens before sleep time, one gets disturbed sleep. Lack of good sleep is known to trigger many medical conditions such as obesity, heart disease, diabetes, dementia, and depression.
The orange lights also lead to reduced melatonin production. However, they are far less effective at signaling to the pineal gland to reduce melatonin production. Thus, if one were to use indoor lights as one approaches bedtime, the orange lights are better than the blue ones.
Typically, one to two hours before sleep time, one should turn off all the sources of blue lights. They are fluorescent household lights or digital screens such as mobiles and computers. If one needs lights, one should use orange or incandescent lights.
- All lights affect the melatonin production. However, the blue rays have the highest frequency amongst the visible lights. So they trigger the pineal gland the most.
- Ideally, one should reduce light of any kind from reaching the eye a little before and during the sleep hours.
- While orange lights are better than blue ones at not triggering the pineal gland, intense orange lights will also attenuate melatonin production significantly.
- Since digital gadgets are small in size, one may not notice their lights. But since they are held closer to the eyes, their display lights can be more disconcerting than the ambient household lights.
- Most digital gadgets have a night mode, wherein the blue lights from the screen image are automatically reduced. While that alters the colour balance of the images to a reddish tone, it is relatively safer for the eyes.
- Many mobile apps have a night mode, in which the display is reversed from black text on white background to white text on black background.
To Read More
- On this website: Blue rays: How to protect eyes from this new threat
- On this website: Dark side of bright lights
- The National Institute for Occupational Safety and Health (NIOSH): The Color of the Light Affects the Circadian Rhythms
- Harvard Medical School: Blue Light has a Dark Side
- PNNL: Blue Light? Orange Light?
- Healthline: Do Some Types of Light Help You Sleep Better?
First published on: 12th December 2021
Image credit: Matheus Bertelli on Pexels