Understanding circadian rhythms.

Jonathan Rush

Jonathan Rush, Partner

How light affects our health and wellbeing.

Part one of our five-part series exploring the latest thinking in circadian lighting – in celebration of the International Day of Light on 16 May.

When one considers the lighting expert’s impact on the interior environment, it’s fair to say we have never had such influence. Solutions have moved from the functional to the aspirational, with a growing trend for spaces to be designed for people in order to enhance their health and wellbeing.

A vital aspect of health and wellbeing is healthy sleep. Disrupted, poor, or inconstant sleep can have a negative impact on our bodies. Not only does it increase risks of serious illnesses, it also impacts alertness, mood, and mental wellness.

Sleep and circadian rhythms.

We have 37 trillion cells in our body each with its own timeclock. For our bodies to function and sleep properly, it’s vital that each cell is in proper synchronisation; this is done by the suprachiasmatic nucleus (SCN), a tiny area of the brain located within the hypothalamus.

The suprachiasmatic nucleus acts as our main timeclock, entraining within our cells what is best described as our body-clock or our ‘circadian rhythm’.

Essentially our circadian rhythm regulates a 24-hour cycle of sleep, wake, hunger, alertness, hormone release, and body temperature… and generally keeps us healthy.

But, as a night-shift worker or arctic explorer will testify, this rhythm can become desynchronised and have major impacts on our health & wellbeing. Night-shift workers, for example, have higher rates of obesity, diabetes, heart attacks, and cancer.

Light’s influence.

Light is arguably one of the biggest influences on our circadian rhythm: 

Our retinas have non-image forming cells called Photosensitive Retinal Ganglion Cells, whose only role is to receive light and subsequently determine if it is night or day.

– These cells are more sensitive to blue light and, should they not receive adequate light for two hours, send a message to our SCN.

– Our SCN, in turn, communicates with the pineal gland, which starts the secretion of the melatonin hormone.

– The increase in melatonin makes us sleep and, in turn, triggers the aforementioned cycles of hormone release necessary for a healthy sleep cycle.

Ultimately, what all this tells us is that lighting – both daylight and artificial – plays a vital role in our circadian rhythms… and therefore our health and wellbeing.

Considering we spend so much of our time journeying through the built environment, it’s vital that we explore the possibilities for circadian-centric lighting design within our spaces. There’s a great deal of excitement about the potential wellbeing impacts that this new understanding gives to the lighting design of interior spaces.

In tomorrow’s article, I outline how sophisticated circadian lighting has become a viable option in the right circumstances.