The way light alters circadian rhythm depends on the timing of light exposure. In modern society, though, electricity creates an abundance of light sources that affect the brain’s circadian pacemaker. When exposed to only natural light, a person’s circadian rhythm becomes closely synchronized with sunrise and sunset, staying awake during the day and sleeping when it’s dark. The brain then sends signals throughout the body to control organs and other systems in accordance with that time of day. When light enters the eye, it is sensed by a special group of cells on the retina, which is carried to the brain and interpreted as information about the time of day. This rhythm is controlled by a small part of the brain, known as the circadian pacemaker, that is powerfully influenced by light exposure. Circadian RhythmsĬircadian rhythm is a 24-hour internal clock that coordinates a wide range of processes in the body, including sleep. Light has dramatic effects on sleep, influencing circadian rhythm, melatonin production, and sleep cycles. Learning about the complex links between light and sleep allows you to set up your bedroom to be more conducive to consistent, high-quality sleep. From streetlights to office lighting to cell phones, artificial light is a constant part of modern life, brightening homes and the nighttime sky.ĭaily light exposure, including the type of light we see as well as when and how long we’re exposed to it, has a critical effect on sleep. While human biology evolved with sleep following the daily patterns of sunlight and darkness, ubiquitous electricity makes 24/7 illumination possible. Light also affects the production of melatonin, an essential sleep-promoting hormone. Light plays a central role in regulating circadian rhythm, the body’s internal clock that signals when to be alert and when to rest. While most people intuitively know that it’s easier to sleep when it’s dark, the link between light and sleep goes much deeper. Light is the most important external factor affecting sleep.

Lights out 2