Module 2. The Color of the Light Affects Circadian Rhythms | NIOSH (2024)

FAQs

How the color of the light affects the circadian rhythms? ›

Exposing the eyes to blue light (or white light, which includes blue light) during the sensitive periods triggers photoreceptors in the retina to send a signal to suppress melatonin and shift circadian rhythms. These photoreceptors do not respond to red light and minimally respond to yellow and orange light.

Circadian rhythms are the physical, mental, and behavioral changes an organism experiences over a 24-hour cycle. Light and dark have the biggest influence on circadian rhythms, but food intake, stress, physical activity, social environment, and temperature also affect them.

Research studies discovered red to be the best color light to help you sleep, because it increases production of melatonin as well as full darkness. On the other end of the spectrum, blue is the worst. Despite being a calm-inducing color on most occasions, blue is not suitable for lighting a bedroom.

For example, red and blue light increases the sense of irritation and reduces the moods relaxation and stability; red light can also reduce the moods calm and pleasure and increase the mood nervousness. To understand how colored lighting regulates mood, scholars have explained the meaning of positive and negative mood.

In general, researchers estimate that light in the evening (about 2 hours before and after usual bedtime) can shift the circadian system about 2 hours later per day, whereas light in the morning (about 1 hour before and after usual wake-up time) can shift it about 1 hour earlier per day.

Blue light not only suppresses melatonin, it also enables the circadian rhythm to help the body maintain alertness.

'Bright shades of yellow and orange are great for helping wake you up in the morning because they are both attention-grabbing, cheerful, and energizing colors that stimulate the brain and make us feel more alert,' explains Vanessa Osorio, a sleep expert and sleep health content specialist at Sleepopolis.

Green light can reset the circadian rhythm through melatonin, the hormone that regulates our sleep-wake cycles. A special photoreceptor system in the human eye picks up light and elicits nonvisual responses, sending signals to the brain to reset the body's internal clock and altering melatonin production levels.

Limit caffeine, alcohol, nicotine, and some medicines, especially close to bedtime. Manage your exposure to light. Light is the strongest signal in the environment to help reset your sleep-wake cycle. You may need more sunlight during the day and less artificial light at night from TV screens and electronic devices.

What disrupts circadian rhythm? ›

Continuous lighting, noise, overnight patient-care interactions, mechanical ventilation, pain, surgery,²¹ fatigue, stress, sedation, and critical illness itself, all disrupt the normal circadian rhythm (Figure 2). Many factors in a clinical setting lead to a disrupted circadian rhythm.

Circadian rhythms are regulated by small nuclei in the middle of the brain. They are called the suprachiasmatic nuclei (SCN). Nuclei act as control centers. The SCN are connected to other parts of the brain.

The best night light colors for sleep are red and amber, as they are warm and soothing colors that promote a good night's sleep. It's thought that colors close to red on the light spectrum stimulate melatonin production. Red light has a lower color temperature than regular sunlight, making it ideal for sleep.

Blue light therapy is often claimed to help mood disorders and anxiety perhaps by influencing the biological clock.

Light blues are known to feel more soothing and healing, while dark blue is more intense. Blue light is meant to be relaxing and can reduce anxiousness. Use blue in your bedroom when you're looking to spend the night in and just chill and relax on the couch.

In order from lowest frequency to highest, they are red, orange, yellow, green, blue, indigo, and violet. Because of the inverse relationship, they are reversed in order by wavelength. The color with the highest frequency is violet.

Brain cells tend to be the most sensitive to blue wavelengths and the least sensitive to red wavelengths. Blue wavelengths can even have an impact on those who are blind when it comes to circadian rhythms. Red/amber light is the least likely hue of light to impact our internal clocks.