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What is Circadian Lighting?

What is Human centric or Circadian Lighting?

There’s been quite a bit of talk about human centric or circadian lighting and how LEDs can improve productivity in workplaces or make the residents of nursing homes more comfortable. Essentially, circadian lighting involves changing the colour temperature and brightness of lighting at certain times of day to both optimise alertness and stimulate the sleep response. Circadian simply refers to people’s natural 24-hour sleep/wake cycle.

Natural rhythms

People are sensitive to light levels and produce the hormone associated with sleep, melatonin, as it becomes dark. It’s only recently been confirmed that there are photosensitive cells in the eye that initiate this crucial process. Exposure to blue light or light of high colour temperature interferes with this natural response and keeps people from getting enough sleep. Similarly, people who get very little exposure to natural daylight have their circadian rhythms disturbed. Many sleep experts recommend that you avoid using devices that emit cool light in the hours before bed.


LEDs have made the changing of colour temperatures and intensities at set times much easier. Several places including nursing homes, schools and hospitals have experimented with changing light levels to match the variations of natural light. Some claim that workers can be energised by strong blue light in office environments, but the most promising application for this emerging trend is in aged care.

All day, every day

Old folk in nursing homes, especially those with Alzheimer’s, are exposed to low levels of illumination. Many spend virtually all day, every day inside and see little sunshine. Several studies have found that the disturbed sleep patterns of residents with dementia can be improved by tailoring the light to replicate the variations of dawn till dusk with soft warm light in the morning giving way to strong blue light at midday and then easing back to warm light in the evening.

Sobering address

Whether the promising results from nursing home experiments will translate into a widespread acceptance of circadian lighting in workplaces and schools is unclear. Despite the lighting industry being keen the commercialise the idea, the leading expert in the area, Dr Russell Foster, delivered a sobering address to the Light + Building 2018 exhibition in Frankfurt, saying: “We can’t develop human-centric lighting until we know what impact light has upon human biology across the day and night cycle”. Not all people respond to light in the same way and there can’t really be a ‘one size fits all’ solution.  But as tuneable LEDs connected to smart systems become more widespread you can expect this fashion of attuning lighting to the rhythms of the day to spread as well.

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