How Light Affects Your Sleep


Nowadays, people spend more time than ever before under different forms of light, such as those emitted from interacting with smartphones, working in front of computers, watching television, etc. Some recent studies indicate that the average American spends over ten hours every day on screen, and the use of digital devices keeps increasing.

Although the light emitted from these devices is substantially less compared to natural sunlight, the rise in the use of these devices poses problems, especially in terms of their effects on the circadian rhythm.

Light regulates human physiology and behavior, affects the internal timing mechanisms of the human brain, and the most obvious is the sleep-wake cycle. Light is one of the factors that cause disrupted sleep, which can be harmful to health. And having a disturbed sleep would generally lead to shorter sleep duration, increased daytime fatigue, and more mediocre daytime cognitive performance.

Overall, low quality of sleep affects our health and the quality of our life. And in this article, we will examine how light affects sleep.

The Effects of Light On the Circadian System

Light is the primary zeitgeber (entraining cue) for the vertebrate circadian system. In mammals, light information is projected to the circadian pacemaker or synchronizer via intrinsically photosensitive retinal ganglion cells (ipRGCs). Light entrainment is modulated, not only by the duration of light exposure but also by its intensity and spectral composition.

Additionally, light can influence sleep timing, duration, structure, and quality. These sleep characteristics and the intensity of sleep are controlled by the circadian drive for wakefulness and the accumulation of homeostatic sleep pressure during preceding wakefulness. Light influences subsequent sleep by either altering the rate of sleep pressure build up or by altering the timing of the circadian-modulated wake drive.

Before the invention of the light bulb, we had no issues with sleep schedules. It was this invention of light bulbs that gave us the ability to lengthen daylight and affected how easy and fast we sleep naturally. 

Our body goes typically into sleepiness the moment it grows dark outside, and this helps to produce more melatonin - a hormone essential four sleep-wake cycle.

However, the different forms of lights emitted in our various houses make it difficult for our bodies to know when it's truly bedtime. Hence, the quality and architecture of sleep is associated with preceding light exposure. Light exposure timing and intensity do modulate not only circadian-driven aspects of sleep but also homeostatic sleep pressure.

How Light Affects Sleep

The amount of light around you controls your brain's production of melatonin, a hormone that makes you feel sleepy. In bright light, you make less melatonin while you produce more melatonin in darkness. Explained below are the different forms of light and the ways they affect sleep.

  • Sunlight: It helps you to wake up in the morning. Cells in the retina of our eyes detect sunlight and send messages to our brain, which keeps active for roughly 24 hours. These light cues trigger all kinds of chemical events in the body, causing changes in our physiology and behavior. Sunlight enables you to feel more alert when you open the blinds and get outside.
  • Light from screens: The “blue" light emitted from devices has a powerful effect on your brain. According to Harvard Medical SCHOOL, IT WAS REVEALED that though blue light boosts attention, mood, and reaction times during the day, it can be the most disruptive at night. Compared to other kinds of light, the blue light affects how we sleep more powerfully. So, you should turn them off about an hour before bed.
  • Artificial light: Bright lights after dark signal the brain to wake up. Several recent pieces of research have revealed that the waking brain is usually more active bright light. Though we might not be conscious of it, we are more mentally agile in bright light. So you should use dim lights and block outside lights in the evening.

Conclusively, sleep is a delicate process that can easily be interfered with. And as you have read, several outside factors play a part in improving or disrupting sleep, including light from artificial sources and temperature ranges. You should, therefore, give more attention to these factors henceforth to enjoy a healthy sleep.