Light Exposure and Circadian Rhythm
Our internal circadian rhythm (also called the circadian clock) is the engine behind our sleep-wake cycle and is itself governed by light exposure. But not all light exposure is equal: the light intensity (or lux) and timing of light exposure impacts circadian rhythm quite differently. For instance, morning light — especially the first natural light of the day — is a powerful wake-up signal due to the ratio of blue light to yellow light that is unique to sunrise and sunset. Additionally, outdoor light exposure can be upwards of ten times brighter than the brightest indoor lighting, creating a much stronger synchronization between your internal clock and the time of day.
At the same time, exposure to bright light, particularly blue light from screens and artificial light late at night, will lead to circadian disruption. Shift work, jet lag, rapid time zone changes, and an inconsistent sleep schedule cause a misalignment between the light levels hitting the photoreceptors in our retinas and the body’s other biological signals for sleepiness including increased melatonin levels and a decrease in body temperature.
The effects of light on our circadian rhythm extend beyond mere sleep timing. Even mild to moderate sleep deprivation has been linked to mental health issues and temporary declines in cognitive functioning. Therefore, regulating our exposure to different light sources throughout the day is a key strategy in promoting overall mental and physical health and performance.
