Circadian lighting design: the significance of what you don’t see

Intrinsically photosensitive retinal ganglion cells

These light receptors, also called ipRGCs, contain the photopigment melanopsin and are connected to the nucleus suprachiasmaticus via the optic nerve. This part of the brain contains our biological clock. Light is directly connected to our biological clock via the optic nerve and plays a crucial role in the regulation of our sleep-wake cycle. This allows us to be active or asleep at the right times of the day.

Humans are by nature active during the day. Without exposure to light in the morning, 85% of the population would go to bed progressively later and get up later. We call this “social jet lag”: we start lagging behind the time of our environment because our hormone production and body processes get disrupted.

Exposure to light with a sufficiently high percentage of short wavelengths, the well-known “blue light,” is the most important mechanism for resynchronizing our biological clock with the environmental time. In our current society, we often sit in spaces that may be adequately lit to perform a visual task but for our biological functioning, most lighting is insufficient. As a result, we can say that we are living in biological darkness.

The impact of circadian lighting design

Impact on cognitive functioning

Light can have an impact on all attention levels, although the most obvious short-term effects have been demonstrated mainly at the level of our basal alertness (how awake or sleepy we are). The updated European standards for ergonomic workplace lighting address a “new” light quantity: MEDI, which takes into account the production of melatonin, the sleep hormone. This topic was discussed in detail during the inspiration events of knowledge platform De Derde Long.

Workers exposed to high MEDI levels in the morning feel more alert and can concentrate better. This in turn improves their job performance and productivity. Children also score better on tests when they were exposed to high MEDI levels in the morning.

Impact on emotional functioning

Many studies by vzw Groen Licht Vlaanderen and KU Leuven, among others, have shown that light therapy is effective in treating various forms of depression (see HCL guide 2020). In the long term, the adaptation of lighting according to HCL (Human Centric Lighting) criteria can lead to an improved emotional state of mind as sleep and circadian rhythms are better balanced. Modified lighting has an immediate energizing effect, just as upbeat music can instantly cheer us up. This could lead to less absenteeism and stronger employee engagement.

By following new health insights, Multiline continues to strive for scientifically sound lighting.