What makes lighting affect sleep quality?
Lighting can affect sleep because the body's internal clock responds to changes in light and darkness. Bright light, particularly in the evening, can signal that it is still daytime and may make it harder for some people to become sleepy. A dark sleeping environment generally supports the body's natural transition toward sleep.
Bright light in the evening
Exposure to bright light before bedtime can delay the body's normal preparation for sleep. This is especially relevant when someone spends the evening under strong room lighting or in front of bright screens.
Reducing unnecessary brightness as bedtime approaches can help create a more suitable environment for winding down.
Blue-rich light
Light from daylight and many electronic screens contains relatively large amounts of short-wavelength, or blue-rich, light. Exposure to this type of light in the evening can have a stronger effect on the body's circadian system than some other types of light.
The effect varies depending on brightness, timing, duration, and the individual. It does not mean that every screen automatically causes poor sleep, but limiting bright screen exposure close to bedtime may be useful for people who find it disruptive.
Darkness during sleep
Even relatively small amounts of light can be noticeable in a dark bedroom. Streetlights, hallway lighting, electronic displays, and light coming through windows can all contribute to nighttime brightness.
Using blackout curtains, an eye mask, or covering unnecessary light sources can help create a darker sleeping environment.
Morning light is different
Light is not simply something to avoid. Morning exposure to natural light helps provide the body with a strong time signal and can support a consistent sleep-wake schedule.
Getting some natural daylight after waking, when practical, can help reinforce the difference between daytime and nighttime.
Screen use before bed
Phones, tablets, computers, and televisions can affect sleep in more than one way. Their light can provide a wake-promoting signal, while the content itself may also keep the brain engaged when someone is trying to relax.
Reducing screen brightness, using warmer display settings, and putting devices aside before bed can be helpful, particularly if screen use makes it difficult to become sleepy.
Bedroom lighting matters
A bedroom does not need to be completely dark while you are getting ready for bed. Warm, dim lighting can be more suitable for winding down than bright overhead lighting.
If a light is needed during the night, a dim light can reduce the amount of bright exposure compared with turning on a strong room light.
A simple lighting routine
A practical approach is to:
- Get natural daylight during the morning and daytime.
- Keep indoor spaces reasonably bright during the day.
- Gradually reduce unnecessary lighting in the evening.
- Limit bright screens close to bedtime if they interfere with sleep.
- Keep the bedroom as dark as is comfortable during sleep.
- Use dim lighting if you need to get up during the night.
Lighting is only one part of good sleep. Noise, temperature, comfort, stress, schedule, and other factors can also affect how well someone sleeps. If sleep problems are persistent or significantly affect daytime functioning, discussing them with a healthcare professional may be appropriate.
