Blue light and light emitting diodes (LEDs)

Blue light plays an important part in keeping our body clock in time with the day and night cycle. Exposure to too much blue light in the evening or at night could disrupt the body clock, causing poor sleep and possible other effects.

Sources of blue light

Blue light is part of the light we get from the sun. We receive most in the middle of the day, and much less at sunrise and sunset. The body has evolved to use these differences to keep our body clocks in time with our surroundings.

Some modern lighting sources, such as LEDs and CFLs (compact fluorescent lamps), can produce relatively high levels of blue light. Computer and phone screens can also produce blue light.

Effects of blue light

Exposure to a lot of blue light in the evenings and at night can disrupt the body clock. This leads to poor sleep and effects on other body processes that depend on the body clock, such as digestion.

The possibility of other effects is also being investigated.

Levels from everyday sources, such as computers, phone displays and LED lights, are too low to cause any damage to the eye.

How to control your exposure to blue light

We need blue light during the daytime to help maintain our natural body rhythms. Being outside or near a window can provide this.

Blue light from lighting can be minimised by choosing LED or CFL bulbs with a ‘warm white’ colour, rather than ‘cool white’ or ‘blue white’. Some bulbs are labelled with a ‘colour temperature’ — choose them with a temperature of 2,700 or 3,000 K.

Computer or phone screens often have a night time setting, which changes the colour balance to reduce the amount of blue light. Do not forget that what you are looking at on the screen can also have an important effect on sleep.