Human-centric lighting: Circadian rhythms and CCT 

For many years, the extent of the influence that lighting has on our mental and physical wellbeing was unknown. It has since been discovered that lighting can affect our sleep, mood and even our behaviour. Because of this, those in the lighting industry have started using human-centric lighting and correlated colour temperature to use light to promote health benefits.
Scientific research has shown that we have an in-built circadian rhythm, which has developed throughout history. This rhythm is informed by light and tells our biological body clock when to be alert and when to be restful. As our ancestors used to spend most of their time outside during the day and sought shelter during dark evenings, their body clock was linked to the natural 24-hour cycle. These days we spend a lot of our time inside, even staying up late at night with the help of artificial light, therefore our rhythm can be disrupted. This can lead to negative consequences such as fatigue, reduced daytime performance and sleep disorders.
A visual representation of human-centric lighting courtesy of LightingEurope and the International Association of Lighting Designers

An aspect of human-centric lighting (HCL) is the use of different colour temperatures to mimic the natural lighting cycle of a 24-hour period, combating the negative effects of circadian disruption. This can be done through either LED technology or by designing a lighting scheme based on where they are going in your house, how you use each room and selecting the most appropriate colour temperature for each light. Put simply, correlated colour temperature (CCT) is a measure of how warm (red/orange/yellow) or cool (blue/white) a light source’s colour is. It is measured by Kelvins (K) and residential lighting generally ranges from 2700K to 4500K.


During the day, constant exposure to blue light stimulates a physiological response of increased heart rate, muscle strength, alertness and productivity. This is a great light to opt for in kitchen/dining areas and the home office. Having a cool light in spaces you occupy in the day will keep your body clock in line with your circadian rhythm, as it would if you were outside in the sunshine. At Lumi Lighting, we offer lights at 4000K, what we call ‘natural white’. During the night in nature, lights edge closer to the red end of the light spectrum. Think of a red/orange sunset. During this time, when blue light is suppressed, melatonin is released in our bodies. Melatonin is the hormone that contributes to the relaxation and sleepiness you feel at night. Choose Lumi Lighting’s 3000K lights, also known as ‘warm white’, in rooms such as the bedroom, to help you become more relaxed and sleepy in the evening.

An indication of correlated colour temperatures throughout the day courtesy of Ledrise.

Human-centric lighting can be used to maintain the natural rhythm of your body clock, by choosing correlated colour temperatures in lights to mimic that of a natural 24-hour cycle. By choosing wisely, you can maintain alertness during the day and a peaceful, deep sleep at night. Human-centric lighting is an effective tool useful to improve sleep, mood and general wellbeing.